Posts tagged #quicklime

What Type of Lime Should You Use for Tanning and Rawhide?

I remember many years ago trying to understand what type of lime I should use for tanning and being really confused.  This video and blog post are an attempt to foster a basic understanding of lime as well as which type to use and where to find it.

Lime is used in tanning to loosen the hair for removal, and sort of clean the skin fiber of unwanted substances.  It is used in the same way for processing rawhide as well as skin for making glue.  While there are other alternatives, lime was most commonly used in 18th and 19th century tanning processes and by home tanners since.  It is easy to use, accessible, safe, predictable and does he job well.

What we call lime exists in a cycle.  There are three stages in the cycle and once the cycle is completed, it could theoretically be started over again.  Only one of the stages is useful for tanning and in the majority of other arts.

The first phase is the one in which lime naturally occurs.  That is as calcium carbonate.  Calcium Carbonate is what shells and limestone are made from, the natural materials from which we make the lime that we use.  This form would include chalk, limestone, dolomite, marl, marble, shells and coral.  Calcium carbonate is fairly inert and stable.  Ground limestone or ground shells can be used as a soil amendment to raise ph and provide calcium, but not for tanning.

Shell, limestone and marble, three common forms of calcium carbonate.  Any of the stones may have any number of impurities, Magnesium being very common.  Shells are probably ideal for tanning use since they are very pure being almost all calcium carbonate.  They are also very easy to turn into lime.

If we heat calcium carbonate up red hot we end up with Calcium Oxide aka quicklime.  Qucklime is mostly an interim stage, though it has some uses in the arts and industries.  As relates to tanning, it is an interim stage.  If you read old tanning books that say to use quicklime, but that is because they acquired quicklime and slaked it immediately into the the next form for use.  Quicklime is easy to transport because it is very light, and it just made sense in the old days to order freshly burned quicklime and transport it that way. It would then be slaked immediately as it does not keep well.

Quicklime, also known as lime shells whether made of shells or rocks.  As far as tanning goes, quicklime is just an interim stage.  Voraciously thirsty, unstable and highly reactive, lime shells should be processed immediately.  When quicklime is mentioned in old tanning literature it is often stated something like "take fresh burned lime".  Easy to transport because of their light weight, lime shells were often delivered fresh and slaked immediately in the liming pits.

When we add water to quicklime, it produces Calcium hydroxide in one of two forms.  If we add a lot of water to the quicklime we end up with lime putty.  If we add only a little water, the quicklime disintegrates into a fine powder that can be stored dry.  

The dry powder, Dry lime hydrate is what you can easily buy for processing hides for tanning.  It is available at hardware stores as "type S lime" or "builders lime" and according to some of my viewer/readers as "barn lime" in some parts of the country sold for spreading on barn floors.  Just make sure that you are not getting dolomite or agricultural lime which is just ground up rocks.

Dry lime hydrate, the stuff you can get at the local building supply, is made using small amounts of water, which causes the burned quicklime to disintegrate into a fine powder.  This process doesn't always work on shells.  At least use hot water with shells, then it might work.  Really though, you should make lime putty at home.  It is more stable and more potent than the dry hydrated lime.

Lime putty can be made at home. It is more potent than dry hydrate and less apt to go bad since all you have to do to preserve it is keep it under a layer of water where it will keep indefinitely.  Either dry hydrate or lime putty can be used in tanning to equally good effect though, you just don't have to use quite as much lime putty.  For more on lime in general and burning lime at home, see the lime page.

To make lime putty, just use more water.  The solids will settle to the bottom of the storage container.

For more on what lime is actually used for, tanning and pre-processing hides, you can see this video on de-hairing.

Related Videos  

Burning Shell Lime in a Primitive Straw/Clay Kiln

Tomorrow/Today is my birthday.  As I sit here at 11:58 pm, sipping tequila out of a bottle, trying to trap a loud and pesky mouse that is rolling bay nuts around the trailer and finishing up posting this project so I can move on to the next one, I want nothing more than to top the 1000 mark on my YouTube subscriptions today.  I have 959 subscribers, so only 41 to go!  If you can share this video somewhere that you think people will truly enjoy it and help me top 1000 subs by the end of the day, I will be just really happy about that.  Small victories you know.

I have two bottles of champagne.  One for reaching 1000 subs and another one for my first really mean and stupid YouTube comment!  YouTube comments are notoriously retarded.  Other YouTubers do entire episodes devoted to the stupid comments that they get, yet I have none!  I feel left out!  Clearly I need more exposure :)

This project was so fun :  I love burning lime, and now I'm thinking about how cool it would be to build something larger using a method similar to the straw kilns I show in these videos.  Something like this ancient style of coiled straw/clay Mexican granary that was the indirect inspiration for my kiln design, via friend and natural builder Michael Smith who saw these in Mexico and then innovated a straw/clay wattle wall system.

Super neat Mexican granary design utilizing straw and clay in a coiled pot type of form.  This would almost surely use much more clay than I'm using.  I'm intrigued though by the idea of using a mix more similar to the pet to build something larger, like a pigeon cote, a smoker, or maybe a bedroom...

Super neat Mexican granary design utilizing straw and clay in a coiled pot type of form.  This would almost surely use much more clay than I'm using.  I'm intrigued though by the idea of using a mix more similar to the pet to build something larger, like a pigeon cote, a smoker, or maybe a bedroom...


I made two videos.  One is the short accessible version and the other is longer and more detailed.  It also introduces two of the new series or categories I've been dreaming up which are intended to make content more navigable and allow people to find the content they want to see more easily. 

The Buildzerker! series houses the short version.  It is a series for shorter general interest versions of projects I do.  For every person out there who is ready to know how to burn and slake lime in some detail, there must be hundreds that just think it's interesting to watch, or who might be influenced in some positive way simply by seeing it happen.  Buildzerker! is a way to entertain people, while planting seeds that may someday grow.  When anyone is ready, the long version is there.  I'm very happy with this effort.  It is fast paced, visually interesting and even beautiful, while covering a subject that is truly interesting.  I tried as hard as I could to make it worth 7 minutes of almost any persons life.

BuildCult is for more detailed how to versions of projects intended to transmit more knowledge.  This one is also fast paced, but packs a ton of information into 20 minutes, while still having all of the visual interest of the simple version.

I like both of them, and am really looking forward to making more.  I feel like I'm doing what I should be doing, and that's always good.  I hope you have a great day.