I am asked a lot about what tanning materials people should use in their part of the world. Well, be careful what you ask for he he. Here is a very large amount of information to address fill that gap. I had already typed up a partial list for a vegetable tanning book project that I have done some writing on which is mostly presented here (don’t hold your breath on me publishing it anytime soon). That information comes largely from Howe’s book on tanning materials, which I think is still in copyright. But I decided to list a bunch of full text excerpts on tanning materials from some other old out of copyright tanning books. To top it off, at the end there is a surprisingly long bibliography of publications on tanning materials put out by the USDA, with such fun topics as tannin content of some acorns, Tannin content of pacific coast trees, tanning materials in South Africa and the tanning industry of Washington state. There is still much more that could be dug up on the subject. If you want to research a specific material more, you can use sites like googlebooks.com and Archive.org Try different combinations of keywords such and as leather, tanning, tannin, the plant’s common names and the plants botanic name (or names, plural since they often change over the course of 100 years or more in order to keep botanists employed and make them look busy).
Another thing I’d like to point out is that this large body of information illustrates just how common tannins are in plants around the world, and that there is probably something usable where you live, even if you are not seeing it. Even in deserts without trees, there are probably species of shrubs with high tannin contents. An important point however is that not all plants that can be used to tan a hide are actually going to make very good leather. The quality of leather will vary with the tanning material used. That is one reason to test multiple materials if you are forging into experimental territory with unknown plants. Our large oak galls for instance are easy to gather and extremely high in tanning agents. All indications so far though are that those oak galls make a stiff, brittle leather. I would guess that most plants with enough tannin will make at least okay, useable leather for a home tanner. The color will also vary a lot from dark brown, to pinkish, red, light tan and tending toward yellow. You will notice that not infrequently fermentable sugar content is mentioned in the literature. Tanners have often blended materials together to insure adequate fermentation and to impart various qualities; now we are getting into the realm of the real art of leather tanning which is waiting for us to rediscover.
Speaking of color, one of the most common mistakes in Vegetable tanning is to assume that color and tannin are synonymous. Just because your tanning liquor is still colored, doesn’t mean it still has any significant tannins left. Similarly, just because skin is colored all the way through, doesn’t mean it is well tanned yet. The reason this is relevant is that a material could be high in non tannin dye substances which color the skin or the skin could just be partly tanned and not well tanned, and capable of adsorbing a lot more tannin. Tanning of thin skins should progress relatively fast. Just because you can leave a hide in a watery weak solution for 6 months or a year, it doesn’t rot away, and it appears to be penetrated with some color, doesn’t mean that it is well tanned. In fact it is probably not well tanned and is likely damaged.
Don’t mess about with marginal materials if you don’t have to. Unless there is some reason that you just find some exotic or new material especially compelling, favor known tanning materials over very experimental materials at least until you know what you are doing a little bit. I understand that many of you don’t have access to quality known tanning plants, but if you do, favor those over things like coffee grounds, random dead autumn tree leaves, black walnut hulls and used tea leaves. I’ll offer some ideas on where to find materials shortly.
Experimenting: when people first start tanning, they often bite off more than they can chew. Usually there are a lot of mistakes and mishaps involved in the learning process. Tanning is typically a bit of a learning journey, especially using traditional natural tanning methods. If you are going to experiment with tanning materials, EXPERIMENT SMALL! Even something as small as a squirrel skin could be cut into 4 to 6 pieces to test different materials. Pick up road killed squirrels to experiment on. Another option for something larger, like a deer, goat or sheep hide, is to cut off the neck and run through your process with that before attempting to tan the rest of the skin. You can dice that neck up into 8 or 10 pieces and try all kinds of stuff while doing a miniature run through of the process with the very same skin you will be tanning. Another great source of experimental material on bigger skins is to cut off all the legs. A paraplegic piece of leather is quite nearly as useful as one with all it’s limbs. I often cut them off anyway, just because I don’t want to go through the trouble of tanning bits of leather that I probably won’t ever end up using.
Here are some ideas on acquiring materials. Tree barks can often be gotten from road crews, firewood cutters, lumber mills, small portable wood mill owners, and tree trimming professionals. Reach out to these people in your community and you may develop a good relationship with someone that will keep you supplied with bark. For instance large scale firewood cutters typically dispose of piles of bark by burning every year. Keep your eyes peeled for downed limbs and trees after storms, which happens even in cities. If you dry the material carefully and store it dry, it should keep indefinitely. If you live in logging country, drive into a current logging operation or get in immediately after and you can probably score a ton of material. Lumber mills often water the logs over a long period of time, so that can leach and damage the bark, but if they have fresh bark, they will probably give you some.
A few suggestions for various areas of the United States. In much of the East, Sumac is a common plant. Several species in the U.S. are very high in tannins and are excellent tanning materials. Collecting the leaves does not kill the trees and I understand that they commonly grow in waste areas as a weedy plant. In the SouthWest U.S. Canaigre, aka Sand Dock is common and weedy. It is easy to collect and is very high in tannin. You may also have Mesquite, the whole tree, wood included contains tons of tannins and the accounts below are fairly glowing about it’s positive attributes. Willows grow in most temperate parts of the world. They are usually abundant, often growing in areas that no one really cares about and grow back from the roots rapidly when cut down. In fact, some species of willow practically rely on floods and beavers to take the tops out and renew growth. Poplars of various species are common in the north and frequently die of disease or blow over. The same is true of alders in many areas. In the far north you have larch, spruce, willow, alder and uva ursi. Florida probably has many materials, but the Saw Palmetto root is apparetly an excellent tanning material. In any wooded area, it is uncommon not to find at least one downed tree or large limb in any given year within a fairly small area. I heard a gigantic tree fall in the woods just yesterday and another large limb or small tree the previous week.
In spring, bark can usually be peeled right off the wood and dried for later use. A draw knife is a great tool to harvest tree barks that are not peeling off of the wood, for instance in winter when broken trees and limbs are common from snow and storms. Try to shave it off in the thinnest, smallest pieces you can easily manage, so that you don’t have to grind or cut it up as much later. As long as you keep your materials dry, they should last indefinitely.
Tannins are water soluble and if your material is old, dead and rained on, or partially rotted, it is not going to be very good. Dry is totally fine, but not dried and weathered.
Being spoiled with abundant oak bark of numerous species, I have really only used a handful of different materials. I’ve gotten small amounts of tanning materials from other regions brought or sent to me by friends and fellow tanners, but not enough to really gain any true knowledge from. To gain any significant useful knowledge about all the different materials would be a daunting task, nearly impossible, and we should just familiarize ourselves with what we have locally.
I don’t measure the stuff that I use at all. I don’t own a barkometer (yes, there is such a thing) and I don’t want to at this point. I’m more interested in continuing to develop an intuitive feel for how strong to start solutions and how to use the materials that come from my area. My point is that I can’t tell you how much of any particular material to gather, but it’s probably more than you will think to, or want to, gather. I can tell you that in tanning skins with oak bark that I gather here, I use more weight in dry bark than the wet weight of the prepared wet skin.
This quote refers to ground oak bark sprinkled in layers between hides laid in a pit:
“At Sedan, the barkings consist of 85,75 and 65 pounds, that is 225 in the whole, for one hide which when green weighed 100 pounds, and when dry 50.”
The video embedded here shows pit layering of cattle skins with shredded bark.
To translate this excerpt: for each of three times the hides are layered in the pit with bark and left for probably several months each time, the amounts of dry bark applied in each layering were 85lb for the first layering, 75lb for the second, and 65 lbs for the final. This for tanning a 100 pound fully prepared wet skin, a ratio of 2.25 lb bark to 1lb skin. This is an extremely interesting reference, but be cautioned that it only tells us so much. For one, this is an established traditional tanning material, so we know it is of high quality and reasonable tannin content. Other materials may contain more or less. It is using an inefficient method of tanning. When the scientific minded got involved in the tanning industry, they were horrified at the inefficient use of materials in this traditional layered pit tanning, and set about discouraging the practice, looking toward the most thorough extraction methods to get every speck of tannin out and use it to maximum advantage.
The bottom line is there are too many variables to apply broad rules about ratios, and they really don’t apply until we are familiar with a specific material and context. A good starting point for experimenting with new tanning materials might be around 2 or 3 lbs dry material for each 1 lb of wet prepared skin.
Most of the information in this first section is gleaned from from Vegetable Tanning Materials, by F. N. Howes,1953 and Tanning Materials, by Arthur Harvey, 1921 (which you can read here under TANNING MATERIALS) both of which have a lot of good information about materials from all over the world. There is also information from other sources though and some personal experience sprinkled in. The following sections are full excerpts from various old tanning books.
This book has many plants used in tanning listed for India and Pakistan. Useful Plants Of India And Pakistan J.F. Dastur, read free.
Bark is so commonly used, that we often refer to vegetable tanned leather as bark tanned leather. In most barks, the usable tannin is contained in the part that is alive, rather than the outside. In some species the outer dead bark, or “ross” has traditionally been removed, though I have never done that.
“The bad quality of the bark, or of the tan, contributes also to that of the hides; old bark full of crevasses, covered with moss, blackness, or whose fire is extinguished by the moisture it has contracted, forms a bad tannage.” The art of Tanning and of Currying and Leather Dressing.
Tannin content, as well as it’s extractablity, can vary in old v.s. young specimens, but there is no reliable rule to follow since in some species tannin is higher in young, not old barks or vice versa. Further, the tannin may more or less extractable in different ages of trees. Tannin Content varies by season, one source below claiming that spring gathered oak Bark has 4 times the tannin content. That would be convenient, since as far as actually getting the bark off the tree, it is best gathered in the spring when the sap is up and it peels away from the tree easily. Some species peel over a longer season, and for others the window is very short. If the bark is peeling and you cut it into short lengths, it should come off easily by cutting down one side and prying it off with a wedged stick or axe blade. Spring bark probably has a higher carbohydrate content as well. Dry the bark, but never leave it in the rain for any period of time, or the tannins will begin to leach out and mold will form. If a tree is felled or falls on it’s own during the season when the bark is stuck to the wood, you can shave it off in thin layers with a drawknife.
Larch bark: Medium, variable tannin content, L. decidua used in Europe, as a tanning agent, but possibly not very preferred. High sugar content.
*European Larch- Larix decidua synonym europaea 8 to 9% average
*North American- L. xoccidentalis 10.6%
*Asiatic- L. gmelini 9%
Douglas’ Fir: Pseudotsuga menziesii Howe says “7 - 18%, bark of young trees richest; yields light, even coloured well plumped leather”. When I visited the Muir Macdonald bark tannery in oregon many years ago before it closed, they expressed a preference for mature old growth Douglas’ fir bark, which the blended with Quebracho extract. Young bark is certainly easier to come by, and I’ve seen nice leather tanned with it.
Hemlock Bark: Tsuga Can use both Western (heterophylla) and Eastern (canadensis) Species. Eastern hemlock was the basis for a huge tanning industry in the east. It yields a high quality red leather 10 to 11% tannin. Especially good for heavy leathers- shoe soles, harness etc... Western Hemlock: 15 to 16% tannin, store hemlock at least 4 months before using. Reddish color, tanning properties similar to Eastern Hemlock. Sometimes acidified due to low fermentable sugar content.
Spruce: Picea species variable tannin content. European, Picea abies most used in the past. Some of the tannins become insoluble as the bark is dried. This problem can be prevented by steaming the bark briefly before drying. Maybe it is best used fresh? 10-12% average tannin, as low as 5% as high as 18%. Other spruces, Sitka- Picea sitchensis 11-37%; White Spruce- P. glauca21%; Yezo- P. glehnii, 19%; Japan- P. jezoensis 11%; Black Spruce- P. mariana 12%; Colorado Spruce-P. pungens 8.7%
Oak Barks: Quercus species Too many to possibly cover all of them. Most species probably contain appreciable tannin. Thick outer dead bark often removed due to low tannin content. Though not as high on average as some sources, many oak barks are considered excellent for tanning and are often a good place to start if they are accessible in your area. Usually contains lots of fermentable sugars and acids and probably more likely to give good results for beginning tanners than some other materials. Caps and acorns sometimes contain enough tannin to use as well.
Oaks known to be used in tanning (not to say they are the only ones that can be used).
British Isles: Quercus robur synonym Q. pedunculata; Durmast Oak- Q. petraea synonym sessiliflora
Central Europe: Turkey Oak- Q. cerris; woolly oak Q. pubescens
Southern Europe/Mediterranean: Q. cerris, Q. coccifera, Cork Oak Q. suber
North American oaks: White Oak- Q. alba; Chestnut Oak Q. prinus 16%, Swamp White Oak- Quercus bicolor; Scarlet Oak- Q. coccinia; Spanish Oak; Q. falcata; Q. laevis; Q. maxima 11%; Black Oak Q. kellogii; Chestnut oak- Q. montana 11%; Yellow Chestnut Oak- Q. muhlengergii; Pine Oak- Q. palustris; Willow Oak- Q. phellos 10%; Red Oak- Q. rubra 8.7%; Black Oak Q. velutina 8.4%; Live Oak- Q. virginiana 15%;
Tan Oak: Lithocarpus densiflora (recently changed to Notholithocarpus densiflora by people with nothing better to do than confuse us): Not a true oak, but has acorns. Abundant in my area. Central to Northern California. Easy peeling, thick bark, high tannin, makes excellent leather of light color. Use it while you can as it is very susceptible to sudden oak death. Do not transport raw fresh bark that may be contaminated. Tannin is variable, but high for an oak and up to 30%. The bark from the base of the tree is particularly rich. Old trees growing in the sun have the highest tannin. It is valued for heavy leathers. (You can read the entire USDA publication on Tan Oak in the Free Stuff section of this website under TANNING MATERIALS)
Mangrove: Many species, some good for tanning. 10 to 40% with older trees having richer bark. Extract known commercially as Cutch. Tends to make harsh leather, often mixed with other materials.
Wattle, aka Mimosa: Acacia mollissima: 30 to 45% tannin. Australian tree, cultivated in other regions for tan bark where it is harvested every 6 to 10 years. Especially good for heavy leathers,but also light leathers when blended with other materials. Bark at base of tree richest in tannins. Pods are also sometimes used. A. decurrens, a. dealbata, A. pycnantha have also been used in tanning. Other species can also contain appreciable tannin as follows, but not necessarily having been used in tanning- A. acuminata 14-20%; A amoena 23%; A. bancroftii 20%; A. binervata 27-30%; A.brachybotrya 21%; A. cunninghamii 12-18%; A. companata 10%; A. decora 23%; A. elata 27%; A. excelsa 16%; A. falcata 27-37%; A. flaescens 15-22%; A. harpophylla 14-17%; A. implexa 14-22%; A. linifolia 11%; A. leptocarpa 10%; A. maidenii 3-23%; A. microbotrya 19%; A. neriifolia 14%; A. oswaldi 10%; A. penninervis 14-34%; A. podalyriaefolia 8-12%; A pravissima 11%; A. porominens 15%; A. pruinoasa 23%; A. salicina 20%; A. sentis 10-18%; A. vestita 28-33%.
Alder: Alnus species Variable tannin by species, more easily extracted from younger trees. Often mixed with other tannin sources, because it tends to cause brittleness in leather. the seed pods, or “cones” can also be used @ 14 to 26% tannin, or less if rained on, so best gathered as fresh as possible. Alder bark I’ve used in Western N. America lends a reddish or orangish color.
Pine Barks: Pinus species Many species contain appreciable tannin. Notably for North America, where I live, Ponderosa pine 5-11%, Loblolly pine 12%, and Monterey pine 17 to 18%, Pinus Palustris (long leaf) 17-18%, Pinus Echinata (short leaf) 11-18%, Pinus Rigida 14-16%, Pinus Laricio 13% I would suspect that most have enough tannin to use and if you can’t find yours listed anywhere, just try it and find out.
*Aleppo pine- Pinus Halepensis and Calabrian pine- Pinus halepensis var.brutia13-25% used in N. Africa and Mediterranean. Reddish leather.
*Pinus roxburghii, Himalayas11 to 16%; P. khasya, Burma 7 to 10%; P. sylvestris, Europe 16%.
Willow Bark: Salix species Too many species to list. Variable tannin content, but mostly medium. I remember it being known for making soft leather, but I can’t find any reference to back that up. Tannin higher in bark from lower part of the tree.
Birch Bark: Inner bark long used in tanning skins. 11% tannin. Older trees yield more tannin. Pliable, light colored yellowish brown leather. Often mixed with with willow bark, which is similar. Distilled oil from bark also used to treat russian leather.
“Ox-hides require a stronger liquor than any others, and more astringent ingredients ; Birch Trees of three or four years old must be used, or the small branches of birch or chestnut; the Birch makes the best leather ; it is still best if the rind of oak be mixed with the Birch, but they need not be ground so small or so fine for gross Hides, as calve and cow hides.” The Art of Tanning and of Currying Leather 1773
Chestnut Bark: Used as a substitute for oak bark, but said to be inferior. See chestnut wood below.
Eucalyptus: Eucalyptus species.
*Mallet bark Eucalyptus. astringens aka E. occidentalis var. astringens 40 to 55% tannin. Leaches easily with cold water. orange to red. Mixed with other materials or acids to improve plumping.
*Mugga or Red Ironbark, 30-45% tannin, tanning slow, usually mixed with other materials.
*Wandoo and Edunca: both commercial sources of tannin.
*Other Eucalyptus contain enough tannin, and might be worth experimenting with.
Some woods yield tanning material if chipped and cooked.
Quebracho: The basis of a major industry exporting extract used by many tanneries around the world.
Chestnut: Used in Europe and North America. 7 to 20% tannin. Most in heartwood. Probably best more than 25 or 30 years old. Wood dried before extraction. Prickly husks also contain 10-13% tannin.
Oak: Use old heartwood. not particularly high in tannin
Wandoo Eucalyptus: 8-13% in wood, 13-21% in bark. Extracted from fresh wood. Produces firm leather.
Osage Orange, aka Bois D’arc: Maclura pomifera Wood used in tanning tannin 40.6%. Said to brighten or lighten leather color
Mesquite: According to some of the references below, mesquite contains tons of tannin and makes an excellent tan. People I know who live in the SouthWest seem to consider it a weed of the most part.
FRUITS AND NUTS
Myrabolan fruits: Terminalia species 30-32%. Slow penetrating Progallol tannins. Prone to producing low weight spongy leather, so usually blended. Extract at low temps. Also a highly valued medicinal known as Haritaki. I take it.
Pomegranate: Punica granatum bark 10-25%, fruit skins 26% long use in tanning. Also used with alum as a yellow dye for leather.
Acorn Caps Quercus species: Some species have been long used in tanning and even form a commercial industry. I’ve used the gold cup oak Quercus Crysolepis for dyeing skins and it seems to have great potential. If you can’t find information on your species, just try it! Remember to gather fresh caps that haven’t been rained on too much. Species known to have been used for tanning Quercus aegilops 25-31% forms the basis of an industry. called Valonea. Acorns around 6-7%. Valued for heavy leathers. Pyrogallol type tannin with high ellaginannic acid. Used in ground form for layering to give extra weight. High ph value.
Q. tournefortii, Q.ehrenbergii, Q. ungeri, Q. pyrami, Q. ithaburensis, Q. oophor, Q. graeca, Q. macrolepsis, Q. cretica, Q. calliprinos (Kermes oak)
Harvest before rains. Valonea (Q. aegilops is harvested from the trees when ripe) Half developed acorns rejected by the tree in summer (first drop) can be harvested and contain even more tannin than the mature cups.
Acorns: probably used in tanning somewhere, but not all species contain enough tannin to be useful. Caps may be more useful.
THE TANNIN OF SOME ACORNS.
By Henry Trimble.
Contribution from the Chemical Laboratory of the Philadelphia College of Pharmacy. No. 159.
Having been repeatedly questioned concerning the astringent value of acorns, I determined this year to make some tests of them from a few species of oaks. The season just passed has been one in which the oaks of this vicinity fruited abundantly. In a good season the chestnut oak, Quercus prinus, probably yields the greatest amount of fruit, as the acorns are very large ; the white oak, Q. alba, however, bears very abundantly, as shown in the accompanying illustration, Fig. I. A tree covered with fruit is a conspicuous object about the first of September, and until the acorns fall a month later.
In order to refresh the memory of the reader, a sectional illustration of a chestnut oak acorn is shown in Fig. 2.
The several parts of the chestnut oak acorns were assayed for tannin, commencing September first, when they had reached their full size, and continued at intervals until the first of October, when they had fallen. The acorns of this species were taken for investigation because of their large size and abundance, also because they are the fruit of the species of oak whose bark is the most highly prized for its tanning value.
The estimations of tannin were made as soon after the collection of the fruit as possible. It was necessary, therefore, to determine the moisture, and make a calculation of the amount of tannin in the absolutely dry substance, so that in the following results, tannin and ash are both based on the absolutely dry substance.
The cupule usually attracts attention on account of its astringency, and it will be observed that when it is collected during September it is valuable; but the difficulty of collection from the trees would be an industrial drawback, and after it falls the deterioration is considerable, as shown in that collected on October 4th, which collection was from those which had fallen to the ground.
A quantity of the tannin was extracted from the cupules of the chestnut oak, and purified. It resembled, in physical and chemical characters, that of all the oak barks heretofore examined by me, by giving a green - color and precipitate with salts of iron, a precipitate with bromine water, and a pink color with calcium hydrate. On combustion it yielded the following percentages, which are compared with the average composition of the tannins obtained by me from nine species of oak bark:
The following are the percentages of tannin found in the cupules of an number of other oak species.
I am indebted to J. C. Peacock for the preparation, purification and ultimate analyses of the tannin from the cupules of the chest- nut oak ; and to G. H. Maghee for the estimation of the tannin in the cotyledons of chestnut oak, and for repeating my estimations in a number of other cases, thereby confirming them. The hide-powder process was used in all the estimations.
Tannins are very common in plants and if concentrated sufficiently, even low tannin plants could be used to tan skins. I may have leaves that are only 3% tannin, but if several batches are brewed in the same water, a reasonably strong solution might result. But, that is a lot of extra work and if there is something stronger around, I’m probably going to use it. There are long lists of other plants and leaves that maybe used, but below are those that I know were more used and more esteemed, and which have a high tannin content. Obviously, many of the trees that yield tan barks have leaves which also contain tannin. The other factor to consider though, is that tannin content alone doesn’t necessarily make a good or complete tanning material.
Sumach Rhus species: Many species used in various parts of the world and a great choice for home tanners if it grows where you live. Generally very highly regarded. Especially good for light and soft leathers. High in tannin, usually 25% plus. Tannin destroyed by boiling, so extracted instead at 120 to 140 F (50 to 60 C). Species used R. Coriaria (mediterranean, most used. 25-30% pyrogallol, slow penetrating); R. coggygria, Turkish sumach 21 to 30%,; R. myrtifolia (French, Montpellier or Provence sumac less tannin darker color);
Dwarf or Mountain Sumac R. copallina. Considered best of the American sumachs- higher tannin and lighter color. 32%
White, Smooth, Scarlet or Red Sumac R. Glabra 27%
Staghorn, Hairy or Velvet Sumac R. typhina 25%
Read the full USDA Bulletin on sumac as a tanning material in the Free Stuff section under Tanning Materials
Manzanitas: Arctostaphylos species. Many species. Uva Ursi- A. uva ursi leaves and twigs used in Russia for tanning 10-14%; A. glauca in California “has similar properties” Howe. Dozens of species, most in California.
“In Sweedland, they use the bark of the smallest mountain Sallow or Willow, as also of the plant called uva Ursi” The Art of Tanning Currying and of Leather Dressing 1773
Tea Leaves: Not particularly high in tannin to start with and some is leached out in making tea. I would hesitate to try these on anything big, unless you can acquire large quantities, like buckets upon buckets. Howe says they were never used, but I recall reading otherwise somewhere.
Canaigre (Sand Dock, Tanner’s Dock): This is a plant which grows in the western deserts. The leather I’ve seen made from it by friends in the SouthWest has been very nice. The tannins are supposed to be very soluble and penetrate skins readily. It is easy to harvest by all accounts and usually abundant where it grows. Consider yourself lucky if you have ready access to it. Slice thin and dry to store. (20-35% tannin dried, Howe) (18-43% dried, Harvey). Roots 1 year and older contain more tannin. extract at low temperatures, 104 to 113 F to avoid extracting the abundant starch. Catechol type tannin. Read more below and you can download and read the full USDA report on Canaigre Here, under Tanning Materials.
Other Docks, Rumex species: Not widely used, but high in tannins and may be similar to canaigre. Soluble non-tannin content high, usually higher than the tannin content. Some tannin contents of various species are: R. hydrolapathum 21.3% June-11.5% September; R patientia 21.4% April-16.5% june; R. acetosa 22.6% January-20.8% April-15.2% July; R. abyssinicus 15%; R. conglomeratus, Europe 9-10%; R. cordatus, South Africa, 10%; R. crispus, Europe, 3-6%; R. ecklonianus, S. Africa, 6%; R. hasatus, Himalayas, root bark, 21-23%; R. nepalensis, India, 5-6%; R. paluster, Europe, 6%; R. Sanuineus, Europe, 12%.
Galls are abnormal growths of tissue on a plant, usually caused by the deposition of larvae forming eggs into the bark or leaf of the host plant. The larvae live in the gall until they mature. Some are high in tannin and can be used as a tanning material. Harvey says to process at 50 to 60C, 120 to 140F
Oak Galls: Quercus species: Galls from Quercus infectoria, asia minor and Eastern Mediterranean, are the most commonly used. polygalloyl-ellagic acid type. Also may be able to use galls from from Q. Ceris; Q. Ilex, Mediterranean; Q. robur; Q. petraea. I would try any gall from an Oak tree that is available in large quantitiy.
I’ve used the large Galls the grow on Valley White Oaks in California a little bit for tanning and dyeing. The color of the leather is dark brown and my impression is that it is always a stiff and brittle leather.
“At Vienna and in Hungary, they never use Oak bark, but a rug they call Knoupren, and which I believe to be the gall nut ; this is the quickest and most durable tan known ; it may be kept nine months without losing it’s virtue ; very little of it goes to a pit, as they only scatter a small quantity on each hide with their hands. A cow hide may be tanned with this in twenty=four hours. (hmmmm, I don’t know about that)” The Art of Tanning and of Currying Leather 1717
Tamarisk Galls Tamarix species: Best known are from Tamarix aphylla (articulata) and T. gallica. Aphylla used in Morocco for finer grades of sheep and goat skins. Galls are called tak-out or teggaout and come in various grades, the best of which are used for goat skins. Galls are ground, placed in boiling water and skins soaked for 10 days. Also used in Sahara and parts of North Africa. Known in Europe from early times and probably used in the 16th century. Average tannin content 40 to 45%. Regarded similar to oak gall and sumac. Fresh galls produce very light, almost white leather, with rose or violet tint, but skin becomes darker with ageing. Galls of T. Gallica are larger than those from T. Aphylla, but similar in qualities- China and Japan, southern Europe and many parts of Africa. Collect in October or November and dry carefully to avoid fermentation and deterioration. A well developed tree can produce 25 kg of galls a year.
Pistacia Galls: From P. terebinthus, P. vera, P. atlantica, P. khinjuk, P. mutica and P. integerrima
A few more species that have been used in tanning, or may have potential:
Arbutus: Arbutus unedo (strawberry tree) bark and leaves. This is a common landscape tree in California. It is related to both Madrone and Manzanita. Manzanita has been used for tanning. The bark that spontaneously sheds off of Madrone in summer has been used by a friend of mine, and seems worth experimenting with.
Alianthus: A. altissima (tree of heaven) 11%. This is one of the most upleasant smelling plants I’ve ever encountered.
Caffea: Coffee beans
Catalpa: C. longissima, bark,
Ceanothus: C. vlutinus 17% N. Amer. (many species of Ceanothus in North America, most in California).
Cornus amomum, swamp dogwood, 13%, firm leather
Persimmon: Diospyros D. kaki leaves and fruits rich in tannin. A fermented liquor of green persimmons called Kakishibu is made in japan and used to waterproof paper and fabric and to protect steel parts. It doesn’t seem to have been widely favored for tanning, but was apparently used. There is an old U.S. patent claiming it as one ingredient in a process for producing leather.
Walnut: Juglans J. Regia (English or Carpathian walnut) bark only 5%, husks 20%. Everyone asks me about Black Walnut. There are numerous species but no mention in tanning literature that I have seen. Naturaldatabase.com says black walnut hulls contain 45% tannin, this probably refers to the Eastern Black Walnut Juglans Nigra. There is also two Southwestern species, Juglans Major (arizona walnut) and Juglans Microcarpa (dwarf black walnut) and our California Black Walnut, Juglans Californica. I haven’t use any of them for tanning, just for dyeing. I saw a hide tanned with them once that was very dark brown. The tanner said it seemed to take a huge quantity of hulls. It is of minimal interest to me because I don’t like the color. I think that there is probably a lot of coloring matter in the hulls that has no tanning power, so be cautious about the potential to misjudge the strength of the solution.
Myrtle: Vaccinium myrtilus
Palo Verde: Not sure which part is used.
The following verbatim extract is from the book:
The Manufacture of Leather: Being a Description of All of the Processes for the Tanning and Tawing with Bark, Extracts, Chrome and All Modern Tannages in General Use ... with Special Reference to the Best American Practice ...
by Charles Thomas Davis, 1897
Palmetto root.—Palmetto root is found abundantly in Florida, and also grows in Alabama and Louisiana. There is some in Tennessee. It shows 10 percent of tannin. The root can be cut up like bark. The tannin produces tough grain, and strong durable leather. Its action is rapid. Palmetto has long been studied in regard to tanning. It tans rapidly, giving pleasing light color, toughness and pliability, and is a good filler of leather. It has attracted much attention of late years in the south, a tannery using this material having been in operation at Sanford, Fla., for some time. Palmetto is a comparatively new material to leather manufacturers. Its merits will no doubt be fairly tested particularly when offered for sale in the convenient form of extract.
Chestnut oak wood is also for tanning; it is prepared in the form of an extract and is fully described in Chapter V.
Walnut bark from Juglans regia gives a very soft leather, but can only be obtained in small quantities.
Lombardy poplar bark gives a light-brown leather with an odor resembling that of Russia leather.
Elm bark from Ulmus campestris, is especially used in Norway for manufacturing the beautiful Norwegian glove leather.
Horse-chestnut bark, from Aesculus hippocastanum. The bark of this tree contains a tannin which is colored intensely green by ferric oxide. Besides the tannin, which is also found in other parts of the tree, the bark contains fraxin, fraxetin, ajsculin, aesculetin, and aesculetin hydrate, a small quantity of a peculiarly yellow crystalline body and a pectine substance which is decomposed into formic acid, oxalic acid, and protocatechuic acid by boiling potash. The leaves of the horse chestnut* contain also tannic acid, wax, a variety of resin (CMH,,On) and a resinous substance (C„H,.07) possessing a peculiar odor of frankincense. The young leaves and buds contain a peculiar tannin to which Rochleder has applied the term "phyllocitannic acid." Esculotannic Acid.\—Different kinds of tannic acid are found in the horse-chestnut, aesculotannic acid (CMH„0„) occurring, according to Rochleder, in the bark, leaves, flower-buds, ripe and unripe seeds, roots, and the trunk. In a pure state it forms an almost colorless amorphous powder readily soluble in water, spirit of wine and ether. By the action of the air and an alkali, or substances containing oxygen, such as chromic acid, it is decomposed into a brown body having the constitution CMHBOu. Fusing with potash changes aesculotannic acid into phloroglucin and proto-catechuic acid. Ferric chloride colors the tannic acid green. An aqueous extract of the bark comes into commerce under the name of'" horse-chestnut extract." The percentage of tannic acid in the extract varies according to its specific gravity. It is at present much used in Germany and other portions of Europe as an addition in oak-bark tanning, and is said to give good leather. It is considerably cheaper than quercotannic acid. (editor note: the california buckeye Aesculus californica, is closely related. If horsechestnut is so valuable, it might be worth trying, or researching it’s tannin content.)
Willow Bark.—The following are the principal willow barks used in tanning; Salix alba, S. arenaria, S.fragilis, S.purpurea, etc. There is not much difference in the value of the barks, though it is claimed that barks containing salicin, as for instance that of 5. purpurea, are not so good as others. The amount of tannin varies from 6 to 16 per cent. In Russia willow bark is used for tanning Russia leather, and in Sweden and Norway for preparing the well-known Swedish glove leather. The tannic acid contained in willow bark colors ferric salts green, and, when treated with dilute sulphuric acid, yields sugar and possibly gallic acid, though this is doubtful.
Alder Bark contains a high percentage of tannin, amounting, according to Gassincourt, to 36 per cent.
Beech bark from Fagus silvatica mixed with oak bark may be used as a substitute for the latter, but the resulting product is of an inferior quality. It contains according to Davy, 2 per cent. of tannin, and besides a peculiarly red matter and a substance with an odor of vanilla.
Protacea Barks.—The trees from which this tanning material is obtained are indigenous to the Cape and Australia. The principal ones are the Protca canocarpa (knotted tree) and Banksia serrata. The tannin of the latter imparts a beautiful violet-blue color to solutions of ferric salts, while that of the first colors iron green. Both give a brown color with potash lye.
Snouba Bark.—The Aleppo fir (Pinus halepensis) yields two important tanning matarials, namely the snouba bark, and the scorsa rosa. The first is the inner bark of the tree freed entirely from the rind, and comes from Tunis and Algiers.
The scorsa rosa is the rind of the same tree, obtained in Southern Italy, and especially in Sicily, from the living trees ina very rational manner, so that the flesh of the bark remains intact, and produces, like the cork tree, new bark, which is periodically taken off. Snouba bark contains 25 per cent. of tannin, and scorza rosa 13 to 15 per cent. The tannin colors ferric salts green, while it becomes brown by an addition of potash lye.
Ratanhy root is obtained from Krameria triandra, which grows in Peru. The root comes into commerce in a comminuted state, and is very rich in tannin, which is extracted with water, and the resulting solution used as an addition in tanning. The proportion of tannin is, according to Peschir, as much as 42.6 per cent. It corresponds, according to A. Rabe,* with the formula C^H^O,,. It is not a glucoside, and passes, by the splitting off of FLO, over into ratanhy red C,0HlgO8.
Avens root, from Geum urbanum, contains, according to Trommsdorff, up to 41 per cent. of tannin. Solutions of it have occasionally been used as an addition in tanning.
Tormentil root and Sassafras root show a still higher percentage of tannin, the first containing, according to Gassincourt, 46 per cent. of it, and, according to Reinsch, up to 58 per cent. Both roots being very expensive are not often used for tanning.
Geranium wallichianum is a new tanning material which grows in India and contains about 25 per cent. tannin. Leather tanned with it greatly resembles that tanned with canaigre, it being only somewhat darker.
The wood of the Algarobia glandulosa of Gray, mesquite oak, and Quercus virens, live oak, contains much tannin in its entire mass, and is very successfully used in America in place of tan.
Mimosa.—Besides the foregoing, the following tannins have been proposed and occasionally used: Barks of Butea frontosa and Butea gibsonis, both indigenous to the West Indies; fruits of Balsomokarpon brevifolium\, bark of Eucalyptus; Pangue, a root growing in India; Pimica granatum, etc.
TANNING MATERIALS OF THE BRITISH EMPIRE
Tannin content of some Japanese trees, table from The Leather Manufacturer 1921
The following verbatim quote is from Annual Report of the Geological and Agricultural Survey of Texas, 1876
TANNING MATERIAL—SUMAC, OAKS, MESQUITE, ETC.
There are several species of sumac indigenous in Texas, which abound in tannin, vz: Rhus typhina, R. glabra, R. copalina, R. pumila, R. aromatica, R. virens and R. microphylla. The first four of these grow in the eastern and central portion of the State, the three last in the central and western part. In the east, R. copalina is the most abundant, where it and the first species are often associated, both having the common name of sumac and both being used for tannery. Rhus glabra, or the smooth sumac, abounds in swamps, and is poisonous to some people, to others it is harmless. Rhus virens, or the evergreen sumac, grows on limestone hills in the vicinity of Austin and westward to the Rio Grande. It is a short or small tree. Rhus microphylla, or the small leafed sumac, is common on some of the hills of San Saba county, from which it also extends westward to the Rio Grande. It is a large and much branched shrub. R. aromatica is a shrub growing in thickets on hills near Austin and westward to the Rio Grande.
Sumacs abound throughout the larger portion of the State, apparently so common as to seem to be sufficient to supply tannin for all the tanneries in the United States.
In my last report, page 106, a large tannery at Dallas is noticed. This tannery was reported by one of its proprietors, Mr. Dodge, to be making §160,000 worth of leather annually, using largely for tanning purposes the Texas sumac, paying about $20 per ton for its dried leaves and leaf stems. This company report the Texas sumac to be the cheapest, and to make leather equal to the best.
The following analysis of American sumac is taken from the report of the chemist of the Agricultural Department, at Washington, D. C, for 1869:
1. SUMAC FROM GERARDSTOWN, WEST VIRGINIA.
Vegetable fibre 79.20
2. SAMPLE FROM GEORGETOWN, D. C.
Vegetable fibre 81.75
3. SAMPLE FROM FREDERICKSBURG, VA.
Vegetable fibre. 76.50
4. TWO SAMPLES FROM R. T. KNOX & BROS., FREDERICKSBURG, VIRGINIA—AVERAGE OF BOTH.
Vegetable fibre 71.80
These sumacs are of the R. copalina and typhina species, which also grow abundantly in Texas.
These analyses show a great richness in tannin, although some of the samples were not of the first quality, yet they show that we can compete in the foreign markets with the best sumacs.
For the purpose of comparison, I give some analyses of European sumacs, as made by European chemists:
Sumac, first quality, tannin 16.50
Sumac, second quality, tannin 13.00
Gauhe gives us an average of six analyses of European sumac from the countries on the borders of the Mediteranean, 13 per cent. of tannin.
Fine samples of Palermo sumac yield from 22 to 24 per cent of tannin.
Sumac is also used for its coloring matter in dyeing and calico printing. It gives, with a mordant of tin, a yellow; with acetate of iron, a gray or black; and with sulphate of zinc, a brownish yellow. The bark of the smooth sumac (H. glabra) is used as a mordant for red.
The sumacs richest in tannic acid are said to be those which have small dark-green leaves; hence our small leafed western sumac (R. microphylla) must be richer in tannin than any other known American species, because its leaves are very small and also of a very dark green.
Of late years Virginia has had quite a large trade in sumac. It is no»v demonstrated and admitted by consumers in our own country and dealers in Europe, that American sumac, well prepared, is superior in tanning material to most of that in Europe. An importing house, having branches in New York, Philadelphia and Savannah, in a circular to the trade, dated Dec. 31st, 1869, states:
"We would call the attention of the trade, to a very fine Virginian sumac, now being received by us, equal in every respect to the finest Sicily. We recommend its use from the following comparison in the analyses: Finest Sicilian marked with Finest American from Virginia
a lead seal. Pojire and ginia.
ne plus ultra.
Tannin 23.65 Tannin 30.00
Sand 1.00 Sand 50
Vegetable fibre 75.35 Vegetable fibre 69.50
100.00 , 100.00
Alexander Macrae, a produce broker of Liverpool, England, in his Importers' and Exporters' Circular of January 10th, 1870, says:
A great revolution is about to be witnessed in this tanning and dying material. Supplies have commenced to arrive from Virginia, the quality of which is the best that has ever reached Great Britain. The official analysis (Huson), shows that the finest brand of Sicilian, the "ne plus ultra," gives twenty-four and a half per cent of tannin, but the best samples of American (same analysis), yield thirty-one per cent. of tannin.
Yet tons of sumac are wasted annually in Texas, for want of gathering, drying and grinding.
The Dallas Tanning Company have paid $110 per ton for Sicilian sumac. This was before they knew the value of the Texas sumac. For tanning they use Gambier or Terra Japonica, and an extract of oak bark.
Gambier or Terra Japonica, is an astringent substance, sometimes called catechu. It is made by boiling and evaporating the brown hard wood of the acacia catechu, until the juice acquires a proper consistency when strained, and . when cool, coagulates. Imported from the East Indies.
The importance and great value which would result to the State, if the hides which are annually exported were tanned in Texas, leads me to dwell on this subject,and append the following article on the tanning properties of the mesquite tree (Algarobia glandulosa), a genus belonging to the same family as the acacia. The wood of the mesquite has a resemblance to that of the acacia catechu, from which the Terra Japonica is made. The article is from the pen of the; Rev. J. M. Wilson, who has during many years, been principal of high school at Seguin. It was originally published in the Texas Almanac.
Mesquite a Superior Tanning Material.
Besides the value of mesquite for various purposes indicated, it is destined to be a source of vast wealth to Texas and the world, as one of the best known materials for tanning and manufacturing leather. During the war, when we were shut out from the world and cut off from the sources of our supply of the necessaries and comforts of life, we found ourselves under the necessity of meeting these wants from our own resources. Leather was an urgent necessity. Dr. J. Park, then of Seguin, an intelligent gentleman of a scientific turn of mind, directed his attention to the examination of the materials for tanning to be found in Western Texas. He tested the various barks usually used, and found the black jack the richest in tannic acid, live oak the next, and post oak to have the least of the oaks. He then examined the mesquite, and found that the whole body of the wood was rich in tannin. He ascertained that the wood was fully equal to the bark of the black jack in quality and quantity—that it abounded in tannic acid. This was an unexpected and very important discovery. He made practical tests of it, and found it promptly acted in converting the hide into leather of a good quality. He improvised a chopping machine by which he reduced the wood and put it into a form to have the tannin extracted by boiling, and established a tannery, and successfully carried it on for some time after the war. He was so fully satisfied of the value of the mesquite as a tanning material, that he took out a patent for his discovery. The points established by the experiments made with the mesquite are the following, viz:
1st. It is rich in tannin.
2nd. It is cheap, and of inexhaustible abundance.
3rd. By suitable machinery, it may be readily reduced into a form favorable for the extraction of the tannin by boiling or steaming.
4th. It is prompt and effective as a tanning agent in precipitating the gellatin of the hide and converting it into leather. It forms good leather in a shorter time than the tannin of the oak barks.
5th. The quality of the leather is superior.
6th. Its operation is such, from some peculiarity of the tannic acid it yields, that it prevents the decomposition of the hide, so that the tanning process may be successfully carried on during our hot season as well as during the winter.
The difficulty of tanning successfully in this climate during the hot months, with the ordinary tanning materials, is the liability of the hide to decompose or spoil in the centre before the tanning, which is a powerful antiseptic, can reach it so as to preserve it. With other materials the tanning process begins on the external surfaces of the hides, and gradually progresses toward the centre. Hence the liability of the hide to decompose in the middle and become spoiled before it is tanned. The operation of the tannin from the mesquite is different. When a hide is examined, by cutting it after it has been subjected for a sufficient time to the action of the mesquite ooze, it is found that the tannin has penetrated through and through it, and the tanning process has affected its centre as well as its surface. The whole body of the hide is thus preserved, so that there need be no loss from this cause, no matter how hot the weather is. Western Texas has in the mesquite an agent which will exert a very important influence on her future—a source of exhaustless wealth which will enable her to manufacture all her millions of hides into the best of leather—a material in sufficient quantity to manufacture leather for the whole country. Let tanneries, then, spring up. It is a business, properly conducted, highly profitable. And boot and shoe and harness manufacturing should follow, saving in our own country the immense sums we are now paying to enrich other sections and impoverish our own State. J. M. Avilson.
[The great importance of the valuable properties of the mesquite, as stated above by Dr. Avilson, induced us to ask him, if possible, to furnish us with some corroborative evidence in confirmation of his statements, and in reply, he kindly sent us the following letter, inclosing the one from Mr. Coorpender.]
ADDITIONAL EVIDENCE OF THE SUPERIOR TANNING PROPERTIES OF THE MESQUITE.
Near Seguin, July 20, 1869.
W. Richardson, Esq.—Dear Sir—Yours of the 2d inst. came to hand during my absence, or I would have answered sooner.
In your letter, after a favorable notice of my article on the mesquite, you mention: "But when you say the wood itself is superior to the best oak bark, and that it (the tannic acid) penetrates to the middle of the thickest hides simultaneously with its effect on the surface, I fear the assertion may challenge incredulity with many scientific readers." The statement, I confess, in both its parts, seems extraordinary, and if true, it invests the mesquite with great value and interest as a tanning material. The experiments made with the mesquite were confined to Dr. Park, who discovered it. He established a tannery, and conducted it successfully until the close of the war. It then passed into the hands of Mr. R. Coorpender, near Seguin, who carried it on for some time, but was finally compelled, by the difficulty of getting skilled labor, to abandon it. The proof, then, is confined pretty much to the developments of this single tannery, conducted first by Dr. Park and then by Mr. Coorpender. I am sorry I am unable to give a a statement from Dr. Park himself; it would be interesting and satisfactory. He is now living somewhere in Tennessee. I was with him a good deal while he was making his experiments, and we discussed freely the scientific principles involved, and I am well acquainted with the facts and results. He always stated to me that even with his imperfect mode of extracting the tannin—the chips being coarse and his boiling apparatus imperfect—he found the mesquite wood equal to the best black jack bark, and superior to all others. When properly comminuted and extracted, the yield would be larger than from the best bark. The sap of the mesquite, on exposure to the air, becomes tannic acid. In splitting the wood, frequently the tannin or tannic acid, will be met with in circular crystals occupying small cavities in the body of the timber. From experiments made by Dr. Park in making an extract from the mesquite, he was satisfied that the richness of the wood in tannin was such that, with proper appliances, it would be a profitable business to make catechu from it. The catechu of commerce is made from a tree of the same family with the mesquite, the acacia catechu of India.
With regard to the action of the mesquite tannin in striking through and through the hide, instead of beginning on the external surfaces and gradually carrying the tanning process into the interior,. I learn that it is a process which marks some other tanning materials. In a conversation with Dr. Lyon,of San Antonio, an intelligent gentleman who is engaged successfully in the tanning business in a small way, he told me that the bean used in Mexico for tanning, the name of which I have forgotten, and also some other article—perhaps catechu—operated in the same way. It is a highly important quality of a tanning material in the southern country, as it pervades the whole body of the hide with its antiseptic virtue and prevents decomposition. The experiments made during the war in tanning with the barks of the country during hot weather were attended with great loss from the hides spoiling in the middle before the tannin reached it. In cutting the hide, the external surfaces are affected by the tannin, but the middle was decomposed, and the hide would split open. Dr. Park, to show me the manner of the action of the tannin of the mesquite, cut into the hide, and the section revealed plainly that the process had passed entirely through, affecting the centre as well as the surface. It is not to be understood that the whole body of the hide was perfectly tanned, but that colored fibrous lines developed in a few days passed from surface to surface, showing that the whole body of the hide was penetrated by the agent, and secured it against all danger of decomposition. Dr. Park lost no hides after adopting the mesquite, and was satisfied that, with ordinary care and skill, all danger of failure from that source was removed, even in the hottest weather. All the facts revealed respecting the tanning properties of the mesquite convince my mind fully of its excellence—of its special adaptiveness to our climate, and that it offers exhaustless resources for the manufacture of all our hides into leather, and indeed, all the hides of the United States. Farther, I think it will be found that our country, with this material, has advantages over the north in the manufacture of leather, as far, and perhaps in a greater degree, than it has in the manufacture of cotton and woolen goods. The warm temperature of the climate the year round. will hasten the perfecting of the chemical process of making leather, while our climate is also equally in our favor in cotton and woolen manufacture; but the cheapness and abundance of the raw material gives us advantages that must make these manufactures more profitable here than they can be where the raw material has to be imported at great expense. All we want is capital and skilled labor, and these cannot much longer be kept from our country when they can be so profitably employed.
LETTER FROM MR. COORPENDER.
River Side, Near Seguin, July 20th, 1868.
W. Richardson, Esq.—Dear Sir—The Rev. Mr. Wilson read me his reply to your communication calling for additional statements and explanations by way of corroboration of his description of the mesquite as a tanning material. I am happy to be able to state that my experience in the use of the mesquite as a tanning agent confirms in the fullest degree all that Mr. Wilson has written as to its qualities and even more
I will remark that I was connected as a partner with Dr. Park for two years in the tannery. When he left, I carried it on myself for a year, and only abandoned it from the difficulty of procuring skilled labor to carry it on. I will give, under different heads, my views of the mesquite, derived from experience and observation.
1st. As to its richness in tannic acid, according to actual test, it is richer than the best of bark. When properly comminuted, and the tan well extracted, its amount is enormous. The whole body of the tree, limbs, twigs and all, are used.
2nd. The tannin is different in its qualities and its energy as a tanning and antiseptic agent from other tanning materials. Its mode of operating is different from most; others. Instead of being confined to the surfaces, it strikes through and through the hide very promptly. In less than five minutes, a thick hide will show that it has been pervaded by its influence. A simple fact will illustrate its peculiarity in this respect. A negro man who was a practical tanner was asked by Dr. Park, while at work with his material in tanning, how he liked it. "Why,'' says he, "massa, it differs from anything I ever saw. Other things tan as they go, but this strikes right through the hide." This peculiarity was manifest to the negro, and struck him with force. When I stopped operations, I had a few hides on hand. They were about half tanned, and have lain in a very weak ooze for eighteen months without any addition of tan. They are as sound now as the day they were put in. There is no difficulty at all in tanning hides during the hot months. The preserving property of the article is so strong, there is no danger of decomposition. Neither Dr. Park nor myself ever lost any hides, although worked in during the hottest months, while others using bark lost largely.
3rd. With regard to the quality of the leather, I regard it as decidedly better than that made from the usual materials. Workmen in leather pronounce it superior. It is remarkably firm and durable, outlasting northern leather. This fact is so generally understood, that I could sell any amount of it if I had it on hand.
4th. Another peculiarity of mesquite ooze is, that no matter how strong it is when the hide is put in, it never burns the leather or causes the grain to crack. Other strong oozes would ruin the leather. We employed an old tanner, who was raised in a tan-yard, and had worked for thirty-five years at the business; he was greatly delighted with the material, and looked upon it as being the best he ever knew.
The foregoing statement of facts I feel fully authorized to make, from my own observation and experience. I do not feel that they give anything more than a truthful view of the merits of the mesquite. I am fully satisfied it offers to Texas an inexhaustible source of wealth; and it should be a source of large profit to Dr. Park, who has brought it out to a knowledge of the public, and has placed it before the country.
R. J. COORPENDER. .
This and my communication were read to General J. R. Jefferson, of Seguin, an intelligent and practical gentleman. He brought the mesquite to the notice of Dr. Park. He fully sustains the representations made of the mesquite as a tanning agent. He has used and is now using the leather made from it, and regards it the strongest and most durable he ever saw. J. M. Wilson.
Texas has more than fourteen species of oak, all of which have more or less tannin. Experiment shows that oak bark cut in the spring has more tannin by four and a half times than when cut in the winter. It is also more abundant in young than in old trees.
When at Isleta, in El Paso county, Mr. Blanchard of that place showed me a plant used by the Mexicans for tanning. It flowers in early spring, and I did not see its flowers or fruit, but judging from its leaves and roots, it is a species of Rnmex; some of which are called "dock." Polygonum amphibium,. which belongs to the same family of plants, has lately been used for tanning in some of the Western States. This plant abounds in wet places in eastern and northern Texas.
Report of the Governor of Arizona Made to the Secretary of the Interior for the Year 1895
CANAIGRE. Canaigre is the American corruption of the Spanish “cana agria” (sour cane), by which the plant is chiefly known.Canaigre is chiefly remarkable for its tuberous roots, and grows in a wild state in all of the river valleys of Arizona, and, owing to its valuable properties as a tanning material, it is at present receiving much attention by agriculturists. For some time there has been a demand in the commercial world for a good, cheap tanning material as a substitute for the more expensive matter extracted from the oak and hemlock bark, and it is thought that canaigre will fill every requirement. Although the agriculture of this plant is yet in its experimental stage, its utility as a tanning material has been demonstrated, and it is possible that it may yet prove of further value as a food, fuel, and fertilizer.
The conditions favorable to its cultivation are nowhere more perfect than in Arizona. At present a farm of 1,500 acres, 9 miles southwest of Phoenix,.is devoted exclusively to the cultivation of this plant, and the erection in the near future of a factory for the manufacture of canaigre extract is contemplated.
The cultivation of canaigre is destined to be an important industry of this Territory, and the manufacture of its extract a useful and profitable business.
The following extracts are taken from Bulletin No. 21, issued by Professor Forbes, of the University of Arizona, and chemist of the Agricultural Experiment Station:(EDIT, you can read the entire bulletin on Canaigre in the free stuff section of this website under TANNING MATERIALS). LINK
The best conditions for the growth of canaigre are a cool, but not freezing climate, a moderate amount of moisture, sandy, fertile soil, and probably, also, a sunny and arid atmosphere. These conditions are nowhere combined more perfectly or for a longer period of the year than during the six or seven cooler months in the dry, sunny, winter climate of Arizona.
As to locality, canaigre is found most commonly in sandy washes where water is more abundant. With irrigation it will make a good growth in any fertile, tillable grotilind, but the influence of soil conditions on actual production has been little studied. It seems to stand considerable alkali, and is even reported in the salt-grass meadows of Tia Juana Valley, near San Diego, Cal.
As a fuel canaigre bagasse apparently has considerable value. The heating and evaporating power of three samples has been compared with that of an average soft coal and with mesquite wood, which is a leading fuel in the arid Southwest, the comparison of fuel values being made fromthe evaporating powers in each case, which means theknumber of pounds of boiling water which can be evaporated the,oretically by 1 pound of dry fuel. Compared with soft coal canai‘grje bagasse appears to be as 8.87 to 13 in evaporating power, or about two-thirds, while it is even better than in mesquite wood.
Probably an excellent use for canaigre waste is as a fertilizer. When the wet bagasse is piled it ferments vigorously owing to its starchy nature, and shortly rots down to a black mold, rich in organic matter and containing part of the nitrogenous and mineral constituents which the crop removes from the soil.
The canaigre industry is properly concerned with three facts: (1) The demand for canaigre tanning materials; (2) the preparation of extract; (3) the culture of the plant.
THE UTILITY OF CANAIGRE IN TANNING—As regards the value of canaigre tanning materials the writer has been at some pains to obtain the verdict of practicing tanners, and finds that the earlier favorable opinions of tanning chemists have been excellently supported by the experience of the trade. From various sources it is learned that canaigre chips and extracts have been successfully employed, either alone or in connection with other tanning materials, for the production of a remarkable variety of leathers, including both heavier and lighter grades.
‘According to the statements of different tanners it is employed in the production of:
(1) Patent and enameled leathers for the carriage, saddlery, and upholstery trades,
(2) Patent and enameled leather for fine shoes.
(3) Carriage covers and dashboard leather.
(4) A high grade of carriage and furniture leather and a fair grade of patent shoe ti pin .
(5) lgppcr, grain, or similar light leather.
(6) East India kips finished as waxed leather.
(7) . Yellow leather for mittens, horse hides, butts, kangaroo, glazed kid, and other fine shoe leathers. , ‘ , , , ‘
(8) The heaviest sole and harness leather and for the lightest calf and sheep, with best results for all kinds. ‘
The application of cana1gre to such a variety of results is due to various causes, such as the peculiar nature of the union between the hide and the tannins, the effect of color, and that of sugar. With proper management these factors may be so controlled as to produce one or another result.
Some special qualities in leather which may be secured by its use appear from the following extracts:
(1) For light leathers it gives excellent wearing or strain-resisting qualities.
(2) It gives split leather far greater strength than either gambier or hemlock 1quors. , ‘
(3) New canaigre liquor will give a fair color and produce a very fair leather in
(4) The stock plumps very much and fills well after changing into other tanning liquors, and again, canaigre plumps the grain. . - (5) The permanence and speed of canaigre tannage is also noticed by other correspondents.
Certain peculiarities of canaigre seem favorable to its agricultural future: ‘
(1) It grows in winter, when water is more abundant throughout the arid region. ‘ his fact may render possible the reclamation of large tracts of land for which there 1s not suflicient irrigation in summer. I , r, ,
(2) The climate is mild at this season of the year, and labor is therefore more com
fortable and effective.
(3) In case of extreme drought the crop is not lost, but the plant simply stops growth and waits for better conditions.
(4) Harvesting may occur at any time, the mature crop remaining in the ground indefinitely without injury, and even with a certain amount of improvement.
AMERICAN SUMAC: A VALUABLE TANNING MATERIAL AND DYESTUFF.
By F. P. VEITCH, Chemist in Charge, 1918
TANBARK AND TANNING EXTRACT
DEPARTMENT OF COMMERCE AND LABOR
BUREAU OF THE CENSUS
HENRY S. GRAVES,
The following verbatim exerpt is from: Packinghouse Industries, Cottonseed Oil and Products, Manufacture of Leather, Manufacture of Soap, International textbook Company, 1902
General Remarks.—With a view to increasing the number of vegetable tannins available for tanning, diligent researches have been going on for some years. As a result, the number of tanning materials has been greatly increased and their cost lessened.
The economical leaching of bark of late years has served to lengthen the time during which our native barks will be available; the use of wood extracts has also served to protect and increase the life of bark tanning, and as the supply of wood from which these extracts are made is practically unlimited, this generation has nothing to fear as to a shortage of tannins.
Vegetable Tanning Materials.—In the tanning of sole leather, the following vegetable tanning materials are most commonly used:
Hemlock bark is the most important tanning material used in America, about 70 per cent. of all leather made being tanned by it. It is the bark of Abies Canadensis, and in the East contains about 11 per cent. of tannin. The Western hemlock may run as high as 17 percent. of tannin. Leather tanned with it is tougher than that tanned with oak bark, but is not so pliable. Both solid and liquid extracts of hemlock bark are on the market.
Oak bark is also one of the most important tanning materials. It is the inner bark of several varieties of the oak tree, as the English oak (Quercus Robur), the rock-chestnut oak (Quercus monticola), and the yellow oak (Quercus tinctoria). White oak (Quercus alba) and the red oak (Quercus rubra) are not so valuable, because of their lower tannin content and undesirable color. The tannin of the several varieties of oak is known as quercitannic acid CnHtOt. There are four anhydrides of this acid, the first, phlobaphene the second C,tH^Oit, the third Oser's oak red CtlHuOlt, and the fourth Lowe's oak red C„f/,tOlt. Quercitannic acid and phlobaphene only are of importance in tanning.
Canaigre (Rumex hymenosepalus) is a native of the arid Southwest. Some recent attempts have been made to cultivate it and introduce it as a tanning material, but with little success. The coloring matters and starch that are extracted from it affect the quality of the tanned leather.
Quebracho is the name of several hardwood trees growing in South America. The wood and bark of Quebracho colorado contain from 15 to 20 per cent. of a bright-red tannin, but does not contain enough non-tannins to aid the formation of fermentive acids necessary to plumping, nor will it yield a full, well-nourished leather unless combined with other forms of tanning agents richer in non-tannins.
Palmetto root is obtained from the palmetto tree found abundantly in the Southern lowlands. It is attracting considerable attention among the Southern tanneries. The root is cut up and treated like bark. Its action is quick and leather tanned with it is tough.
Gambler (pale catechu) is an important tanning agent. It is the dried extract from the leaves of Uncaria gambier and Uncaria acida. The extract is readily soluble in warm water. It contains, from 36 to 40 per cent. of a brown tannin that rapidly penetrates leather and tends to swell it; taken alone, it produces a soft, porous tannage. It is largely used with other materials for tanning both light and heavy leathers. It is exported from Singapore in pressed blocks and cubes.
Catechu, or cutch, is the dried extract from an East Indian tree, acacia catechu. It contains from 45 to 55 per cent. of a special variety of tannic acid. The extract is evaporated until a thick, dark-brown product is obtained, which solidifies on cooling. In this form it is exported.
Gallnuts, or nutgalls, are excrescences on certain plants, caused by gall flies, which puncture the bark in order to deposit their eggs. Oak gall, or Aleppo galls, and Chinese galls are the most important. The oak gall is formed by the insect on Quercus infectoria. The eggs hatch and the larva develops within the gall. The best galls are gathered before the fly becomes fully developed, and contain from 60 to 70 per cent. of gallotannic acid. The Aleppo galls are the most valuable.
Sumac in all its varieties is a common and valuable tanning agent. It consists of the powdered leaves, stems, and other parts of the so-called tanners' sumac (Rhus coriaria, Rhus typhina, and other varieties of Rhus). The best sumac comes from Sicily. Italian, Spanish, and French sumac is found on the market. It contains from 12 to 25 per cent. of tannin. The American variety, although containing from 6 to 8 per cent. more tannin than the European, is not so valuable on account of a dark coloring matter contained in it, which injures light leathers. When used it is generally mixed with the imported sumac.
Valonia is the commercial name for the acorn cups of several species of oak (Quercus agilops and Quercus maerolepis) coming from Asia Minor and Greece. They contain from 25 to 35 per cent. of tannin, somewhat resembling that of oak bark, but giving a browner color and heavier bloom. It makes a hard, water-resisting leather and is sometimes mixed with oak bark for sole-leather tanning.
Divi divi is the dried seed pods of a South American bush. The pods are about 3 inches long, of a brownish color, and bend in the form of the letter S in drying. These pods contain from 30 to 50 per cent. of a peculiar tannin, somewhat similar to that of valonia.
Myrobalans are the dried fruit of several species of Terminalia from Hindustan, Ceylon, etc. It contains quite a large percentage of tannin. It is generally used mixed with oak bark to modify its color and produces a soft tannage.
6. Classification of Tannins.—The tannins in tanning materials are different members of a, large group of organic bodies, known chemically as tannic acids, or tannins. They differ widely in chemical constitution and reaction, but all have the common property of precipitating gelatine and forming insoluble compounds with animal tissue. They are all compounds of carbon, hydrogen, and oxygen, but their ultimate structure is little understood.
When heated, the natural tannins yield catechol C.H^Of/), or pyrogallol CtHt(OH)t, and sometimes both; this has found a basis of classification. The classification of tannins on these chemical lines bears out an old classification made on the appearance of the tannage.
7. They were formerly divided into tannins that yield the whitish deposit on the surface of the leather, called bloom, and those that do not. Most tannins that give a bloom to the leather are pyrogallol tannics; a solution of their non-tannins when separated has an opalescent appearance. The tannins that give no bloom to leather are classed as catechol tannins.
When treated with sulphuric acid, the pyrogallol tannins yield gallic acid or ellagic acid, the latter combining with tannic acid to form the bloom. Under this treatment the catechol tannins yield the reddish-brown insoluble bodies known to all tanners as reds. These differ from the original tannins in containing fewer molecules of water, and are therefore anhydrides of their especial tannic acids.
Hemlock bark yields a series of these reds; the higher members are soluble, precipitate gelatine, and are the principal coloring materials of the bark. The lower members are insoluble at ordinary temperatures and form the sediments found in the tannery vats.
WOOD AND BARK EXTRACTS
8. General Remarks.—The use of bark and •wood extracts in the process of tanning is becoming more general every year. There are few tanneries where extract is the exclusive tanning agent and but few tanneries where it is not used to some extent. Primarily, an extract is valuable because of the annual decrease of tan bark. It brings the strength of distant virgin forests to the aid of our own failing supply of bark. As a convenient means of quickly strengthening a weak liquor, without the addition of the same amount of insolubles that would be added were the ordinary bark liquor used, it is decidedly useful. The extracts made from some barks and woods are valuable for the color that they impart to inferior tannages on which they may be used.
In sole-leather manufacture, extracts are generally used for strengthening the liquors and occasionally to improve the color of the stock. In some branches of the upper leather industry, the pelts are partially tanned in bark liquors and then finished in liquors made up entirely from extracts, thereby imparting the distinctive characteristics of the tannin of the bark or wood from which the extract was made.
9. Manufacture of Extracts.—This business is carried on to a large extent in this country and of late years in South America. The material to be extracted is ground fine and the leaching takes place in the same manner as at the tannery; details as to the duration of the leaching, temperatures, etc. being determined by the particular substance undergoing extraction. The liquor is then treated by some sort of clarification process, either mechanical or chemical, or both, to remove fine insoluble materials.
Numerous chemical methods of clarification are in use among extract manufacturers. Dried blood and other albuminous products are made use of, which in coagulating envelop the solid particles and settle out. Inorganic processes, such as the use of acetate of lead, or the precipitation of barium sulphate directly in the tank, and many other ways have been devised for purifying, but all remove more or less tannin in addition to the insolubles taken out. Mechanical processes of clarification consist in the settling of the liquor in vast settling tanks or by slow filtration through some coarse fabric.
After clarification, the liquor is pumped to a vacuum pan, where it is reduced in volume by evaporation until the desired consistency is reached. Some extracts are marketed with a specific gravity of 1.22, or 44° Twaddell, others are still further reduced to a specific gravity of 1.26, or 52° Twaddell, and lately solid extracts containing 10 to 15 per cent. water have appeared.
Hemlock-bark extract has been longest on the market. It is made from the common hemlock bark in localities where hemlock is common and shipped to other points not so favored.
Rock-oak bark, chest nut-oak bark and wood, sumac, quercitron, mimosa, quebracho, gambler, and other woods and barks are extracted, and their extracts form valuable adjuncts to the ordinary tan liquor.
Quebracho extract is gaining in popularity with tanners. It is made from the wood of the quebracho tree, a close fibered wood that grows in South America. It produces a fine-colored tannage, but is better adapted to the tanning of upper leather than for sole, as its low non-tannin content tends to keep it "sweet," i. e., does not foster the growth of organic acids necessary to plumping.
The following Verbatim quote is from:
Leather From the Raw Material to the Finished Product, by K. J. Adcock
CHAPTER III TANNING MATERIALS
Tanning materials are derived from the vegetable, mineral, and animal kingdoms.
The vegetable materials used are woods, barks, shrubs, leaves, and fruits, either in their natural state or in the form of extracts. The majority of the minerals have a more or less tanning effect on animal fibres, but the principal are basic chrome salts, formaldehyde, alum and salt. Titanium, iron, cerium and potassium salts also convert skins into leather, but are not yet used commercially.
The animal matters that will convert skins into leather consist of oxidized oils (chamois leather), fats, and brains (crown, Helvetia, or Preller's leather).
Each of these classes of tanning materials has characteristic effects which render them easily distinguishable. The use of combinations of vegetable and mineral tannins has lately increased, and it is possible that the blending of the two classes of materials may produce an ideal tannage for certain classes of leather. In fact, this result is already claimed for a chemically combined tanning material which, according to the American patent, is prepared by the following method: 125 lb. of solid quebracho extract is dissolved in the same weight of hot water and allowed to cool; 16 lb. of commercial caustic soda dissolved in two or three times its weight of water is added, and the mixture agitated about half an hour; 150 lb. of chromium sulphate is then added. In this way an insoluble tannate of chrome is produced, but, on boiling and agitating, it changes to a greenish brown colour and forms a sulphotannate of chrome. The combination of the alum tannage and gambier (a vegetable extract) has been used successfully for years past. Another combination which has given good practical results is the tannage with alum and chrome salts in the manufacture of glove leather.
The vegetable materials containing tannin should be arranged botanically, but the following classification is simpler for practical purposes.
Natural Tanning Materials
1. Barks.—Oak, Hemlock, Pine, Fir, Alder, Khaki, Willow, Cork, Mimosa or Wattle, Babool, Larch, Mangrove, Spruce, Elm, Birch, Pomegranate, Cebil.
2. Leaves, Twigs, etc.—Sumach, Mangrove, Mango, Eucalyptus, Pistacia, Lentiscus.
3. Roots.—Canaigre, Palmetto.
4. Fruits.—Myrobalans, Valonia, Divi-Divi, Cascalote, Mangosteen, Pomegranate, Celavinia, Bablah, Algarobilla.
5. Excrescences.—Gall Nuts, Chinese Galls, Pistacia Galls, Tamarisk Galls.
1. Woods.—Oak, Quebracho, Hemlock, Chestnut, Mimosa, Mangrove, Spruce.
2. Barks.—Oak, Wattle or Mimosa, Larch.
3. Shrubs, Leaves, etc.—Gambier, Cutch, Catechu, Kino, Sumach.
4. Fruits.—Myrobalans, Valonia.
Of these materials, only about twenty are of much importance commercially, the principal being oak, chestnut, quebracho, hemlock, valonia, gambier, myrobalans, mimosa or wattle, sumach, mangrove, divi-divi, spruce, larch, and babool.
Oak Bark (quercus robur) is still an important material, but is rarely used alone. The bark from English oaks contains from 8-14 per cent. of tannin (quercitannic acid) as estimated by the impregnation of a standardized hide powder in a given quantity of the tanning material in solution. Owing to its weakness in tannin compared with other materials, oak bark tans very slowly. Used for sole leather, it would not produce the essential quality of firmness and solidity, and it is now customary to use a stronger tanning material, such as valonia, or valonia extract, or gambier in the latter stages of the process. This is the nearest approach to the pure oak bark tannage of former days, and, if carefully regulated, is a great improvement on the old method.
If dressing hides and calf skins required for boot upper leather are bark-tanned, the tannage is often completed in a sumach liquor, the object in this case being to lighten the colour so that the leather can be dyed evenly.
In England, oak bark is harvested in April and May, when the sap rises in the tree. Rings are cut round the tree soon after it is felled and the bark is peeled from the tree with a special tool which is forced between the bark and the wood. It is peeled in narrow strips about 3 ft. in length, and on delivery to the tannery is stacked in huge ricks. If harvested in a good, dry condition, the bark is said to improve with age, although analytical tests have shown that there is always a certain loss of tannin. An old rick is much darker in colour than a new one, owing to exposure to the air. Coppice bark from young trees is preferred by tanners, as it is free from ross and generally contains more tannin than the rough bark.
In view of the modern demand for materials in extract form, English oak bark would almost certainly be preferred in the form of a concentrated liquid, if the supply of the raw material was plentiful within a limited area. During the last few years it has not met with a ready sale, owing to the large supply of other materials, but it would doubtless regain some of its former popularity if it were prepared in the form of an extract containing about 25 per cent. of tannin. The only oak bark extract on the market is the American chestnut oak (quercus prinus).
Oak Wood is very largely used for the manufacture of tanning extract, especially in Hungary and Canada. The extract contains from 24-28 per cent. of tannin, and is extensively used in the tannage of heavy leathers, as it strengthens the liquors and hastens the process, while keeping the quality of the leather at a high standard.
Valonia (quercus aegilops) is the acorn cups of an oak tree which grows abundantly in Asia Minor and the Greek Archipelago. No other part but the acorn cups is exported. The harvest in Asia Minor takes place in August, when the fruit ripens and the cups can be easily beaten from the trees. They are left to dry on the ground and are then sent to stores in seaport towns, and principally to Smyrna. The drying is still further completed in spacious warehouses, where the cups are spread out and turned over until fermentation ceases. During this process the acorns shrink and are rejected. The cups should be perfectly dried and very hard before export. The Turkish valonia contains from 30 to 35 per cent. of tannin, and is of much better quality than the Greek, which is usually harvested before it is ripe, and, therefore, contains the acorn. As the acorn has practically no tannin value, the Greek valonia contains only 25 to 28 per cent. tannin. There are several grades of valonia, the best going to Russia, Austria, and Italy. English tanners seem to prefer the lower qualities at present, probably because the price is much less than that of the best grade.
The beard of the valonia cup is much richer in tannin than the shell, and, as several of the spines become detached during the storage of the material, there is always a certain quantity of beard (trillo) on offer. This may contain up to 42 per cent. of tannin, but its price is usually the same as that of ordinary valonia. Of late years, very large quantities of valonia have been made into extract at two works in Smyrna. The production of extract will no doubt increase, with a corresponding reduction in the export of the raw material. The great advantages of the extract over the natural cup are its superior strength of tannin (60 to 65 per cent.), easier solubility, uniformity of quality, lower cost per unit of tan, and guaranteed purity.
Valonia is well adapted for the tannage of sole leather in conjunction with oak bark, for it deposits a heavy bloom (ellagic acid), imparts weight and solidity, and increases the resistance of the leather to moisture.
The Chestnut Tree (castanea vesca) probably provides the next tanning material of importance. This must not be confused with the chestnut oak, an American tree which also yields a very useful tannin. The chestnut is indigenous to the South of France and Italy, where the forests have been considerably reduced in size to meet the great demand for this popular tanning material. The greater part of the denuded forests have not been replanted with the chestnut, as the land has been put under cultivation whenever possible. A further depletion has been caused by the ravages of an insect, which turns the interior of the wood quite black and renders it unfit for tanning purposes. It will, naturally, be several years before the supply is exhausted, even if no reafforestation is undertaken. As it is the most important tanning material grown in France, and the chestnuts are used as a food, steps may be taken to cultivate the trees on areas unsuitable for agriculture. Liquid chestnut extract contains from 30 to 32 per cent. of tannin, and, when decolorised, gives a light brown colour to the leather. It is rarely, if ever, used alone, but generally in conjunction with quebracho, valonia or myrobalan extracts.
The Chestnut Oak Tree is indigenous to America and the wood yields a very good tanning extract, containing up to 30 per cent. of tannin. This material is the principal tanning agent used in America, where the tannages are roughly classified in three sections: (1) oak, (2) hemlock, and (3) the union (i.e., a mixture of hemlock and oak). American tanners also use other materials to a smaller extent, chiefly for blending with the principal tannins. Quebracho and spruce extracts are specially favoured.
Quebracho Colorado is a tree indigenous to South America, the best wood for tanning purposes being found in the Gran Chaco district in the north of Argentina, and in Uruguay. The wood contains from 17 to 22 per cent. of tannin, and is so hard and heavy that it sinks in water. In fact, its name is derived from two Portuguese words meaning "axe-breaker."
After felling the trees, they are cut up into logs about 4 ft. in length and either exported in this state to Hamburg, Havre, and Liverpool, or sent to the numerous factories in close proximity to the forests to be made into extract, in which an enormous trade has of late years been developed. Very little of the natural material is now used, as, even after cutting the wood into chips, the tannin is extracted only with great difficulty, whereas the extract can be treated with sulphites, alkalies, or neradol (the artificial tannin) to render it easily soluble, besides which the concentration of the material raises the percentage of its tannin to 65 or even 70 per cent. Owing, perhaps, to faulty preparation, this tanning extract was not well received at first, but it is now among the principal tannins and increases in importance every year.
Myrobalans is the unripe fruit of an Indian tree (terminalia chebula) and contains from 35 to 40 per cent. of tannin which gives a light colour to leather. This material is useful both for light and heavy leathers, but is generally used in admixture with other tannins. It deposits much bloom (ellagic acid) and is largely used for brightening the dark colour produced by other tannins. A large quantity of this material is now made into extracts, which are more convenient to handle and more uniform in strength of tannin. Natural myrobalans have the appearance of shrivelled nutmegs, except that they are yellowish in colour; they are very hard and require a special milling machine to reduce them to powder. The quality of myrobalan nuts varies in different districts, the best being Bhimlies and Jubbalpores.
Sumach is a valuable tanning material, and is used for a large proportion of the light and fancy leathers. It is a small bush plant which grows in Italy, Spain, Southern France, America, and Algeria, but of the numerous varieties the Sicilian (rhus coriaria) is by far the most important. Sumach is one of the few materials cultivated on an extensive scale; most tanning materials are derived from natural sources and, chiefly owing to the length of time before trees reach maturity, it would not be a paying proposition to cultivate them. The sumach shrubs are propagated from small cuttings and the leaves can be picked at the end of the first year, but it is better to allow the shrubs to become more firmly established before stripping them. The leaves are dried and sometimes exported whole, especially for the use of the silk manufacturers in Lyons; but they are more often ground to a fine powder. All sumachs should be ventilated to remove foreign matters and all traces of iron, which would cause dark bluish stains on the leather. "Ventilation" is effected by passing currents of air, preferably with a fan, through a narrow room, when the pure sumach is sent forward, while the heavier particles of dirt and small pieces of wood remain behind. Sometimes the process is repeated, and the best brands of sumach are generally described as "pure, extra ventilated." As far as possible, the male plants (mascolino sommacco) are cultivated in Sicily, where the best sumach is grown. Female sumach (femminello sommacco), grown in parts of Italy, is weaker in tannin than the male, but is rarely sold separately. The serious amount of adulteration formerly practised by the admixture of inferior plants, and particularly of lentisco (pistacia lentisco) led to the Italian Government taking strong action a few years ago, and it is now possible, for a very small sum, to have any consignment inspected and analysed by the Government. Lentisco is now sold separately and is used for common work.
Sumach has been successfully introduced into Australia, but its development is retarded owing to difficulties of labour, which render competition with the European product almost impossible. An inferior sumach (rhus glabra) is grown in America, chiefly in the State of Virginia. It contains from 15 to 20 per cent. of tannin, and produces a darker coloured leather than Sicilian, the best qualities of which contain 27 to 30 per cent. of tannin.
A useful test for finding out if a sumach has been adulterated is to treat a small quantity with strong nitric acid, which destroys the structure of the leaves. The mass is washed and neutralised with an alkali, when the appearance of the midrib and veins of the leaves of the common adulterants are easily recognized.
Sumach is not so much used for shoe upper leather as it formerly was, but it is the best tanning agent for many kinds of fancy light leathers, such as bookbinding, calf, and skivers (the grain of split sheep skins), moroccos, furniture leather, etc. It is also less subject to the action of the air and gaslight than any other tanning material, and is strongly recommended for tanning purposes by a special committee appointed by the Society of Arts to enquire into causes of the rapid decay of leather bindings. Sumach is very useful for brightening up the colour of leather tanned with darker tannins, and is frequently used for improving the colour of both dressing and sole leather. By itself, it yields an almost white leather which affords a good foundation for the most delicate shades.
Gambier or Terra Japonica (uncaria gambir) is a crude extract of a shrub indigenous to the Malay Peninsula. Nearly the whole of the production is shipped from Singapore. The leaves and twigs are boiled in an iron vessel, and when the mass has become syrupy it is strained through a rough sieve into a shallow tub, where it is cooled. The liquor is stirred while cooling and rapidly thickens. Before it sets, it is cut into 1 in. cubes and thoroughly dried. Good qualities contain from 50-65 per cent. of tannin. An inferior product, called "block gambier," is made by allowing the syrupy mass to set in large blocks weighing about 2 cwt. each. These are packed in coarse matting. The strength of tannin varies from 30 to 40 per cent. Gambier is a good tanning material, but its use has been declining for some years past owing to its being frequently adulterated with sago and other farinaceous plants. However, a pure gambier extract, manufactured on the latest scientific principles, has been placed on the market, and there will undoubtedly be a revival of the use of this valuable tannin. This pure gambier is prepared at Asahan, in Sumatra, and is guaranteed to contain a minimum of 38 per cent. of tannin.
Gambier can be used to advantage in keeping up the strength of bark liquors in the tannage of sole leather and hastening the process, while it may be used alone for the tannage of boot upper leather and dressing hides. It produces an exceptionally mellow and plump leather. It is preferable, however, to complete a gambier tannage with a little oak wood or quebracho extract, in order to fix the tannin principle of gambier, which, perhaps on account of its viscosity, does not readily combine with the fibres of the skin.
Mangrove or Mangle, a tree found on the coasts of several tropical countries, yields a useful bark for tanning purposes. At low tide, these trees show their great arched roots standing high above the ground. The best varieties, the ceriops species, are found in the East Indies and Bengal, and the bark of these is said to contain sometimes nearly 40 per cent. of tannin. Other varieties contain from 15 to 25 per cent. The bark is generally made into a solid extract, or "cutch," in which form it contains more than 60 per cent. of tannin, It is useful to blend with other materials, such as oak wood, chestnut, and quebracho extracts, but used by itself it imparts a strong reddish colour to the leather. Some of the Indian varieties are used as dyeing materials, and act as a satisfactory mordant in dyeing leather a dark shade.
Mimosa or Wattle trees, which belong to the acacia species, yield bark rich in tannin. Australia is the native country of several varieties, including the Black Wattle (acacia pycnantha), the Golden Wattle (A. longifolia), and the Green Wattle (A. decurrens).
The bark contains from 20 to 45 per cent. of tannin. The cultivation of wattle in Australia seems to have declined, owing to the high cost of labour and inability to compete with the mimosa bark imported from South Africa, where it is cultivated on a very large scale and where labour conditions are more favourable for the growers, as is clearly shown by the fact that the wattle growers in Australia successfully petitioned the Government a short time ago to place a duty of £1 10s. per ton on the imported bark.
The introduction of the industry into South Africa was quite an interesting adventure. A Mr. Vanderplank brought the seeds from Australia to England about seventy years ago, and afterwards took them to South Africa, where, in recognition of certain services a few months after his arrival, he was granted a farm by the Dutch Government. He then planted the seeds of the black wattle, which grew so well that it was only a question of developing the industry. It was some years before any African bark was exported, and only £11 worth was shipped in 1886. In 1911, the exports had risen to £288,000.
Wattle trees can be grown on soil that is unsuitable for agriculture, and there is every prospect of the industry expanding in South Africa, where a factory has lately been established for the purpose of converting the bark into an extract, which, it is said, will contain between 50 and 60 per cent. of tannin. By far the greater proportion of wattle bark is still exported in the natural form, ground or chopped, and packed into bags weighing about 1 cwt. each. Before the European War nearly the whole of the bark was shipped to Hamburg, English tanners taking very little interest in it, although it was largely used by German tanners. But since the supplies of the materials favoured by British tanners have become somewhat restricted, attention has been drawn to the value of mimosa bark.
Divi-Divi (caesalpinia coriaria) is the dried pods of a Central American tree. It has also been successfully cultivated in India. The pods are rich in tannin, containing anything from 40-50 per cent., but its value is discounted by its liability to fermentation, which, however, may be checked to some extent by the use of antiseptics, such as carbolic acid, formaldehyde, or by the addition of synthetic tannin, neradol. If this tendency to fermentation and oxidation of the colouring matter could be checked completely, divi-divi would be a valuable material, as it makes a firm leather of good colour. When dried, the pods curl up in the shape of the letters S and C. The tannin is found in the husks of the pod. The seeds, which contain no tannin, are so hard that it has not yet been found profitable to extract the oil from them. Very similar tanning materials to divi-divi are cascalote, indigenous to Mexico, and algarobilla (caesalpinia brevifolia) which grows in Chili. Cascalote is chiefly used by Mexican tanners and is rarely exported. Algarobilla is not available in large quantities, otherwise it would be largely used in Great Britain, as it does not ferment so readily as divi-divi, and is even richer in tannin.
Celavinia (also spelt celavina and cevalina) has been on the English market since 1905, but has only lately been sold in large quantities. The scarcity of some of the popular tanning materials since the outbreak of the European War resulted in enquiries for materials that were very little known, and celavinia has proved worthy of attention. It consists of the seed pods of the tree caesalpinia tinctoria, which grows abundantly in certain districts of Central and South America. The pod is from 4 to 6 in. long and is flaky when dried. It contains 30 to 32 per cent, of tannin of the pyrogallol class, and gives a very light-coloured and almost white leather. It is the only pyrogallol tannin which does not deposit bloom, or ellagic acid, on the leather. It may be used as a substitute for sumach in tanning, but has not the same bleaching effect in the retanning process. A tanning extract of celavinia would be useful for some classes of light leathers, where paleness of tint is important. It is difficult to make a second extraction of tannin in the case of the natural material, as, after the first extraction, it forms a soft pulp, through which water will not easily percolate.
Hemlock (abies canadiensis) is an important tanning material, both the bark and the wood being extensively used in America. The wood is now generally converted into extracts in factories built near the principal forests. Of late years, this extract has been imported into the United Kingdom in fairly large quantities, in order to produce a cheap red sole leather to compete with the American hemlock-tanned leather. It contains only about 25 per cent. of tannin, but its value is increased by its contents of insoluble non-tannins, which give weight and solidity to the leather. Hemlock really gives a strong, durable leather, but in America the practice of using artificial weighing materials, such as glucose and Epsom salts, with a reduced quantity of tanning material, has considerably lowered the value of this leather.
In addition to the materials described, there are several of minor importance which can only be briefly mentioned.
Larch Bark is obtained from the tree larix Europea, which is found in Scotland and North Europe. It contains 10-12 per cent. of tannin, which gives a light colour and pleasant odour to leather. Scotch basils (sheep skins) are tanned with this bark.
Birch Bark, from the white birch, betula alba, is another aromatic tanning material. It contains only about 5 per cent. of tannin, and is, therefore, generally used with other tanning materials. It contains a tar which imparts an agreeable scent to the leather that protects it from the ravages of insects. In conjunction with willow bark (salix arenaria) it is used in the tanning process for the real Russia leather. An oil containing the scent can be extracted from the birch bark by dry distillation, and this extract is sometimes used during the dyeing process, in the manufacture of imitation Russia leather, which, however, only retains the scent for a few months, whereas the real Russia leather has a permanent odour.
Canaigre (rumex hymenosepalum) is the tuberous root of a dock plant indigenous to Mexico and the Southern States of America. It is fairly rich in tannin (25-30 per cent.) and yields a moderately firm leather. It contains too large a proportion of starch, however, and cannot be described as a really satisfactory tannin. Moreover, it is not harvested economically and the only way to make a satisfactory tannin of it is to convert it into extract and remove the starchy matters near the source of supply, if anyone dare take the risk of establishing a factory in Mexico.
Bablah or Babool (acacia arabica or acacia vera) grows in India, Egypt, and the Sudan. The bark of the babool tree is one of the principal tanning materials used in India for hides, calf, and sheep skins, which are sent in large quantities to Great Britain in a rough-tanned state and dressed there. It contains 15-20 per cent. of tannin, which readily oxidises in the leather in contact with light, turning into a bright pink colour. It also seems to weaken the fibres of animal tissues, and, for that reason, babool-tanned leather was condemned by the Society of Arts Commission on Bookbinding.
The pods contain from 20-30 per cent. of tannin and give a mellow and plump leather similar to that produced by gambier. The bleaching of the material is troublesome, and it is probable that its use would be increased if the tannin were prepared in the form of extract.
Cutch is a crude extract made from the Indian tree acacia catechu. This is the real cutch, as distinguished from the mangrove "cutch." It is very rich in tannin (50-60 per cent.), but contains a large proportion of insoluble matter and is, therefore, very little used for tanning. It is well adapted for the dyeing of dark colours or black with mineral strikers, such as chrome and iron salts; but its chief use is for tanning fishermen's nets, which it renders waterproof.
Commercial tannic acid, used for medicinal purposes, is prepared from galls or excrescences on oak trees growing in Asia Minor. These galls are caused by an insect (cynips) puncturing the small branches and producing abnormal growth in the perforated parts. The acid is gallotannic, which, if used for making leather, would produce a soft, spongy, and nearly white leather. This tanning material is used a little by Near Eastern tanners, but the result is unsatisfactory.
A selected Bibliography of North American Forestry,
United States Department of Agriculture, 1940
TANBARK AND TANNINS
Alsop, W. К
(15466) The Analysis Of Chestnut Wood. Jour. Amer. Leather Chem. Assoc. 4 (4): 95-99. 1909.
Andrews, H. I., and Clark, R. H.
(15467) The Tannin Content Of Pacific Coast Conifers. Jour. Indus, and Engin. Chem. 13: 1020-1027. 1921.
Baker, H. D.
(15468) Mangrove Bark INDUSTRY For Australia. U. S. Daily Cons. Rept. 146: 1136. 1910.
(15469) Manufacture Of Oak Extract In Japan. Jour. Amer. Leather Chem. Assoc 13 (7) : 305-313. 1918.
Benson, H. K., and Jones, F. M.
(15470) Tannin Content Of Pacific Coast Trees. Jour. Indus, and Engin. Chem. 9: 1096-1098. 1917.
and Thompson, T. G.
(15471) The Tannin Content Of Pacific Coast Conifers. Jour. Indus, and Engin. Chem. 7: 915-916, illus. 1915.
Boomer, J. F.
(15472) Tanning Industry Of The Philippines. U. S. Daily Cons. Kept. 150: 14321433. 1915.
Bosworth, C. E.
(15473) Philippine Mangrove Bark Resources. U. S. Daily Cons. Rept. 236: 118-119. 1917.
Brock, H. G.
(15474) Chilean Tanning Industry. U. S. Daily Cous. Rept. 124: 780. 1918.
Carter, J. C.
(15475) Red Mangrove Nark In Madaoascar. U. S. Daily Cons. Rept. 20: 385-387. 1912.
Champion Fibre Co.
(15476) The Story Of Chestnut Extract. 24 pp., illus. Canton, N. C. 1917.
Chute, H. O.
Tannins And Dye-wood Extracts. Chem. and Metall. Engin. 23 (10) : 468. 1920.
Clark, R. H., and Andrews, H. L
(1547S) Tub Tannin Content Of Pacific Coast Conifers. Jour. Indus, and Engin. Chem. 13: 1026-1027. 1921.
Coding, F. W.
(15479) Quebracho For Tanning; Plata River Region Source Of Supply. U. S. Dailv Cons. Rept. 3600: 1-2. 1909.
Coombs, F. A., Alcock, F., and Stelling, A.
(15480) Comparative Tests With Mangrove And Wattle Barks. Jour. Amer. Leather Chem. Assoc. 12 ( 5) : 158-169. 1917.
Craft, H. M.
(15481) Wattle: A New Industry. 15 pp. San Francisco. 18S2.
Cross. S. H.
(15482) RAW MATERIAL FOR TANNING ABUNDANT IN THE BELGIAN CONGO. U. S. Dept.
Com.. Bur. Foreign and Dom. Com., Com. Repts. 31: 731. 1921. Davidson, P. В., and Sherrard, E. C.
(15483) THE TANNIN CONTENT OF ALASKAN MOUNTAIN HEMLOCK BARK (TSUGA MER
TBNSIANA). Jour. Amer. Leather Chem. Assoc. 23 ( 8) : 371-372. 192S.
Dow, E. A.
(15484) Tanning Extracts Made From Hemlock Bark. U. S. Daily Cons. Rept. 224: 1133. 1916.
Durland, W. D.
(15485) The Quebracho Industry Of The Argentine. Timborman 24 ( 7): 175. 1923.
Edwakdes, V. P.
(15488) Hemlock Bark As A Source Of Tannin. Chem. Engin. 27 (8) : 178-182, illus 1919.
(15487) Paper Mill Bark As Tanning Material. Paper 24 ( 24) : 18-21, illus. 1919.
Edwards, P. L.
(1548S) HOLLAND TO MANUFACTURE OAK TANNING EXTRACT. TJ. S. Dept. Com.. Bur
Foreign and Dom. Com., Com. Repts. 250: 429. 1918.
F Bear, William.
(154S9) Analysis Of Several Varieties Of Chestnut. Pa. Agr. Expt. Sta. BuIL 16: 12-18. 1891.
Frey, R. AV.
(15490) Tannin Content Of Chestnut Stumps And Roots. U. S. Dept. Agr. Yearbook 1926: 697-698. 1927.
Goding, F. W.
(15491) Quebracho For Tanning; Plata River Region Source Of Supply. U. S. Daily Cons. Rept. 3600: 1-2. 1909.
Gottschalk, А. L. M.
(15492) BRAZILIAN TANNING AND DYEING MATERIALS. U. S. Dflily СОПЗ. Rept. 103:
(15493) SUPPLY OF BRAZILIAN MANGROVE BARK OFFERED. U. S. Daily Cons. Rept. 107:
(15494) Tanning Materials In Brazil. U. S. Daily Cons. Rept. 250: 363. 1915.
Gravait, G. F.
CHESTNUT BLIGHT DOES NOT MEAN EARLY END OF TANNIN-EXTRACT INDUSTRY.
U. S. Dept. Agr. Yearbook 1930: 160-162, illus. 1930.
Griffith, R. W.
(15496) Chestnut Wood In The Tanning Industry. Jour. Forestry 22: 542-545. 1924.
Grondal, B. L. (
15497) The Tanning Industry In The State Of Washington. West Coast Lumberman 42 ( 495) : 34-41. 1922.
Hale, H. M.
(15498) Consumption Of Tanbark In 1905. U. S. Dept. Agr., Forest Serv. Circ. 42, 4 pp. 1906.
Hamilton, J. H.
(15499) The Waste Of Hemlock Bauk In в. o. Canad. Forestry Jour. 13 (9) : 12851287. 1917.
Hanson, G. M.
(15500) сотен For Tanning And Dyeing. U. S. Daily Cons. Rept. 57: 958-959. 1916.
Hoar, H. M.
(15501) QUEBRACHO: THE ORIGIN AND GROWTH OF THE INLUSTRY AND THE SIGNIFICANCE OF ITS CONTROL TO THE LEATHER INDUSTRY OF THE UNITED STATES. D. S. Dept. Com.. Bur. Foreign and Dom. Com., Trade Inform. Bull. 295, Tanning Material Survey, pt. 3, 32 pp. 1924.
Kern, E. J., and Wilson, J. A.
(15502) THE TRUE TANNING VALUE OF VEGETABLE TANNING MATERIALS. Jour. IndllS. and
Engin. Chera. 12 : 415-419. 1920. Kerr, G. H.
THE MANUFACTURE OF CHESTNUT EXTRACT IN THE UNITED STATES. Jour. Amer.
Leather Chem. Assoc. 5 : 485-505. 1910.
Lamb, E. M.
(15504) Tanning Materials In South AFRICA. U. S. Dally Cons. Rept. 254: 428429. 1915.
(15505) The Development Of The Chrome Tanning Industry In The United States Of America. Jour. Amer. Leather Chem. Assoc. 14 (11) : 599-613. 1919.
Mclean, Arthur. (15506) Production Of Divi-Divi In Dominican Republic. U. S. Daily Cons. Rept. 120: 708. 1918.
Mattoon, M. A.
(15507) Logs And Leather: The Chestnut, From Tree то Tannin. Amer. Forests and Forest Life 32: 669-671, illus. 1926.
(15508) Experiments With Tanning Stuffs In Madras. U. S. Dept. Com., Bur. Foreign and Dom. Com., Com. Repts. 269: 633. 1918.
Merritt, H. F.
(15509) Quebracho As A Tanning Material. U. S. Cons. Rept. 49 (182) : 269-271. 1895.
Michael, W. H.
(15510) Tanning In India. U. S. Dally Cons. Rept. 3208 : 7. 1908.
Monroe, C. E., and Chatard. Т. М.
(15511 ) Tanning Materials. Twelfth Census, U. S. (1900), Census Repts. 10: 585589. 1002.
Myers, D. J. D.
(15512) QUEBRACHO EXTRACT STOCKS AND PRODUCTION FOR 191!). U. S. Dept. Com., Bur.
Foreign and Dom. Coin., Com. Repts. 171: 441. 1919.
Nelson, R. M., and Gravatt, G. F.
(15513) Tue Tannin Content Of Dead Chestnut Trees. Jour. Amer. Leather Cbem. Assoc. 24 (9) : 479-499, illus. 1929.
Nieren Stun, M.
(15514 ) REPORT ON THE TANNING MATERIALS AND MANUFACTURE OF LEATHER IN JAMAICA.
Jamaica Dept. Agr. Bull. 4: 121-126. 1906. Nihoul. E.
(15515) THE SYNTHETIC TANNINS AND THEIR USE IN TANKING. Sei. АтвГ. Monthlv 1
(4) : 32(5-330. 1920.
Norton, T. H.
(15516) Tanning Materials Of Latin America. U. S. Dept. Com., Bur. Foreign and Dom. Com., Spe. Agents Ser. 165. 32 pp., Шиз. 1918.
Parker, ,T. G., and Blockey, F. A.
(15517) RELATIVE TANNING VALUES OF DIFFERENT SPECIES OF MYROBALAN8. Oil, Paint
and Drug Reporter 65 (1) : 24-27. 1904.
Phillips, R. O.
(15518) Manufacture Of Quebracho Extract. CJiem. and Metall. Engin. 32 (13): 611-614. 1925.
PlNKEBTON, J. L.
(15519) The Wattle Industry In Natal. U. S. Dept. Com., Bur. Foreign and Dom. Com., Com. Repts. 23: 650-651. 1924.
Record, S. J.
(155201) HARVESTING TAN BARK AND THE PROBLEM OF MEETING THE DEMAND IN THE
Future. Sei. Amer. Sup. 74: 408^09, illus. 1913.
(15521) OUR PRESENT AND FUTURE SOURCES OF VEGETABLE TANNINS. Set Amer. 114 (23):
580-581, 603-604, illus. 1916.
Rohrman, F. A.
(15522) Tannin From Western Hemlock. Timberman 27 (9) : 202. 1926.
Soauone, С. C., and Merrill, D. R.
(15523) The Tannin Content Of Redwood. Jour. Indus, and Engin. Chem. 11: 643-644. 1919.
Sohneiderhan, F. J.
(15524) THE BLACK WALNUT (JUGLANS NIGRA L.) As A Cause Of The Death Of Apple Trees. Phytopathology 17: 529-540, illus. 1927.
Smith, J. A.
(15525) Development Of The Tanning Industry In India. U. S. Dept Com. Bur. Foreign and Dom. Com., Com. Repts. 246: 388-394. 1919.
Stewart, N. B.
(15526) Natal Wattle Bark For United States. U. S. Daily Cons. Rept 155: 89. 1913.
Templeton, H. L., and Sherraed, E. C.
(15527) Tannin Content Of Western Hemlock After Immersion In Sea Water. Indus, and Engin. Chem. 18: 101-102. 1926.
(15528) Mangrove Tannin. Pa. Univ. Bot. Lab. Contrib. 1: 50-55. 1892.
(15529) Materials Used Fob Tanning. Jour. Franklin Inst 123: 442-449. 1887.
(15530) ON THE TANNING PROPERTIES OF THE BARK OF THREE NORTH AMERICAN TREES.
Gard, and Forest 8: 293. 1895.
(155«) Tannin Of Some Acorns. Amer. Jour. Pharm. 68: 601-604. 1896.
(15532) The Tannins. 2 v. Philadelphia. 1892-94.
(15533) The Tannins Of The Palmettos. Gard, and Forest 9: 182-183. 1806.
(15534) Tannin Value Of Some NORTH American Trees. Gard, and Forest ft: 162163. 1896.
United States Bureau Of Foreign And Domestic Commerce, Hide And Leather Division.
(15534A) Tanning Materials SURVEY, Parts 1-я. U. S. Dept. Com., Bur. Foreign and Dom. Com., Trade Inform. Bulls. 107, 211, 295. 1924.
Veitch. F. P.
(15535) A DISCUSSION OF METHODS FOR THE ESTIMATION OF TANNIN. U. S. Dept. Agr.,
Bur. Chem. Bull. 90: 215-218. 1905.
(15536)THE EXTRACTION OF TANNING MATERIALS WITH DIFFERENT EXTRACTORS. U. S.
Dept. Agr., Bur. Chem. Bull. 90: 212-214. 1905.
(15537) Tanning Materials. In Bailey, L. H., Cyclopedia of American Agriculture, v. 2. pp. 623-629, illus. 1907.
and Rogers, J. S.
(15538) AMERICAN SUMAC; A VALUABLE TANNING MATERIAL AND DYE STUFF. U. S. Dept.
Agr. Bull. 706, 12 pp., illus. 1918.
Westwood, R. W.
(15539) Tannin For Strengthening Leather. Nature Mag. 4 ( 2): 87-89, illus. 1924.
Wilbur. D. F.
(15540) Tannic Extracts From Chestnut And Other Woods. U. S. Daily Cons. Rept. 207: 866. 1917.
Wiley. S. H.
(15541) Paraguayan woods Containing Tannin. U. S. Daily Cons. Rept. 243: 236. 1915.
(15542) Latin America As A Source Of TanninG Materials. Chem. and Metall. Engin. 30 (8) : 303-305, illus. 1924.
(15543) LATIN AMERICA'S GREATEST CONTRIBUTION TO THE TANNING INDUSTRY : QUEBRACHO.
Chem. and Metall. Engin. 30 ( 9) : 344-346, illus. 1924.
(15544) Tanning Materials Of Latin America. Chem. and Metall. Engin. 30 (10): 3; 8-399. illus. 1924.
WOLESENSKY, EDWARD. (15545) INVESTIGATION OF SYNTHETIC TANNINO MATERIALS. U. S. Dept. Com., Bur.
Standards, Tcchnol. Paper 302, -15 pp. 1925.
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