Cuir-Bouilli-art - 8/25/14
"Hardening Leather" by The Honorable Christophe of Grey.
This article was submitted to me by the author for inclusion in this set of files, called Stefan's Florilegium.
These files are available on the Internet at: http://www.florilegium.org
Copyright to the contents of this file remains with the author or translator.
While the author will likely give permission for this work to be reprinted in SCA type publications, please check with the author first or check for any permissions granted at the end of this file.
Mark S. Harris...AKA:..Stefan li Rous
stefan at florilegium.org
You can find more of this author's work on his website at:
This article was first published in the "The Phoenix", the newsletter of the Barony of Sacred Stone, Atlantia.
by The Honorable Christophe of Grey
Cuir Bouilli is the term for hardening leather. In this article I am going to shatter some well-established SCA myths about hardening leather and discuss techniques for hardening leather.
The big myth of how to harden leather perpetuated in the SCA is to boil the leather in wax. Yes, this works. You end up with hard leather that is waxy and really not very comfortable to use, i.e. as armor, on a hot day as the wax tends to come off on everything. Boiling in wax is NOT the only way to harden leather.
Let’s first discuss what really happens to leather when it gets hardened. The myth of boiling in wax also supports the myth that the wax gets in the pores of the leather, fills them up and makes the leather stiffer. Fantasy! To make leather stiff/hard, you need only raise it to a temperature of 120 degrees and hold it there for about 10 minutes, sometimes more for larger projects. What happens during this heating is the molecular structure of the leather actually undergoes a change called elastomerization. This is what makes the leather stiff/hard. You can over harden leather. Try it. Cut a one inch square of leather and drop it in boiling water until it turns black. Lift it out of the water and let it cool. The first thing you will notice is that the piece has shrunk to about 3/4 inch square. It will also be VERY stiff. However, if you place it on a hard surface and hit it with a hammer it shatters like cheap plastic.
Well then, how do you harden leather? Remember the key is to raise the leather to 120 degrees F and hold it at that temperature for about 10 minutes. You can do this several different ways, which I’ll discuss next.
Water hardening – You can dip your project into boiling water. Be very careful to not leave it in too long thus having the project turn black and go through the process discussed above. When you dip your project into boiling water it will get very hot. I know, duh! But when you bring it out it will not be hard/stiff. In fact it will be very pliable. Shape the project as you desire then let it cool. When it is cool it will be hard. A side benefit of using this hot water technique is that the leather becomes very elastic while hot allowing you to shape and stretch it. This is one way to make formed elbow cops out of leather. Thus, find an item that your elbow can fit inside. Boil your leather until it is hot and pliable. Stretch and form it over the item you have and let it cool. You just made a formed elbow cop.
Another hot water method that works well for smaller projects is to pre-heat your oven to 200 degrees F. Then wet the project by either dunking it in water and shaking off the excess water or misting it with a flower mister/sprayer. Place the project in the oven and leave for about 10 minutes. By turning off the oven if you forget your project it won’t bake to the ultra hard black state. If you only leave the project in for 10 minutes it will be hot and pliable when you bring it out. Same form then cool process as above.
Wax hardening – As mentioned above, this technique works. The literature says you can melt your wax then ladle it over the project to harden it. I have never had any luck with this technique as the leather never really gets hot enough for the elastomerization process to occur. You can dunk your project into the melted wax, leave it for a bit, then remove it. This works like the boiling water method but now you have to deal with all the wax. You also have to deal with the issue of melting a very flammable substance for the process. Wax will catch fire from an electric heat source just as easily as from an open flame.
There are other ways to harden leather that do not involve boiling wax or water. One of the most period methods that would today be the least desirable is to soak the project in urine. Yipper Fred, just pee on your armor after every battle for about a month and you will have very hard leather. Of course you will also stink so bad no one will want to be within two counties of you…………maybe that’s why they did it in period ….. hmmmmmm. Soaking leather in urea is also a method for tanning leather.
One way to harden leather that most of us have already experienced is using salt. If you have a leather item that you wear on hot days you sweat on it. Over time the salts from your sweat will harden the leather. Think about those old work boots you use for working in the yard. You have sweat in them and never really cleaned them up. After a while they get real stiff.
One of the beauties of hardened leather is that you can re-heat it and re-shape it. Let’s say your vambrace fit before but now, after a year of working out, your forearms are massive (we all wish). You can actually re-heat your vambrace and re-shape it to your new arm.
Now a few comments about finishing off a hardened leather project. For this, let’s think armor. If you want to do any stamping or tooling, do that before you harden. If you try to do it afterwards your results will not be nearly as good. First off the piece will now be hard and shaped to your body part so you can’t lay it flat on a hard surface for stamping or tooling. Secondly the leather will accept the stamping of tooling inconsistently. That is, some impressions will be nice and deep and clean others won’t be.
After you have hardened the project, then you can add color. Use dyes, antiques or acrylic paints. They all work fine. Finish off with a nice finish coat of Super Sheene, Bag Coat, or Atom Wax. For maintenance of armor, because you will be sweating in it a lot, you can clean it up periodically with saddle soap. This will not soften the leather – no heat.
Copyright 2014 by John Atkins. <cogworks at triad.rr.com>. Permission is granted for republication in SCA-related publications, provided the author is credited. Addresses change, but a reasonable attempt should be made to ensure that the author is notified of the publication and if possible receives a copy.
If this article is reprinted in a publication, please place a notice in the publication that you found this article in the Florilegium. I would also appreciate an email to myself, so that I can track which articles are being reprinted. Thanks. -Stefan.