Hardened leather was used for armor from classical antiquity through the end of the Elizabethan era. Its popu1arity can be trace to its strength, weight, and relative ease of manufacture.
For this method of hardening you will need a good sized double boiler, a large supply of wax (paraffin works very well), candle wax hardener, candle wax dye (both are available at a good hobby shop), and, of course, a supply of leather.
The minimum thickness of leather you should use is about 8 oz.
(1/8")
to 11 oz. (3/16"). Sole leather, which is
about 10-14 oz. (1/4") thick, is very efficient and has great stopping power. Very heavy leather (such as bulls throat) is
superlative.
For small plates, the simple immersion method is best; I will deal with hardening larger plates later on in the article.
Always use a double boiler to melt wax. The boiler I use is a
large kettle that I no longer love, which rests on three legs inside a larger
kettle which is filled halfway with water.
Put in your wax: after it melts, add about half again as much hardener as the manufacturer recommends. Since you are going to be inside this leather, you want it very rigid.
If you want to dye the leather, add the dye at this point. Make certain that you have enough wax to complete the
job at one sitting. If you run out halfway through you will have a wretched time mixing a new batch that matches the original. Always use a test piece of leather, and let it dry completely before you decide you like it. If you don't use dye, the leather will usually turn a very rich, dark brown, which I personally prefer to dyed leather.
Now, the actual mechanics of the hardening. Take about five or
ten plates and drop them into the wax.
About fifteen seconds after you immerse the plates, you will see a stream of air bubbles rising from the leather. Wait until these bubbles have completely stopped rising, and remove the leather. This will take anywhere from two to ten minutes, depending on your leather. Place the plates smooth (grain) side up, on waxed paper or foil. Don't use newspaper, the plates
willl stick to it. Once you have the process down, you can produce an unbelievable number of plates in an evening.
For any plate too large to fit into your boiler you will have to take a few risks and do the hardening in your oven. I can hear your castle's cook screaming already.
Melt a good quantity of wax in your double boiler, as you would for small plates. Use a brush to coat the plates completely with wax. The wax should be about 1/4 of
an inch thick. Put the plates onto an old cookie sheet, and then pour on more liquid wax.
Set your oven to bake at about 150 degrees. Don't use broil; you'll ruin an expensive piece of Ieather and create a stench that must be smelled to be believed.
Place your leather into the oven and watch it carefully. "Baste" the leather with liquid wax at least
once a minute. If necessary be sloppy, just never let the leather dry.
When your leather is quite saturated with wax, remove it and start shaping. The sane way is to put on work gloves, hold the leather in your hands. and shape it. This method only produces and approximate fit. A second method (practiced by our local shire's Armorsmiths and Masochists Guild) calls for putting on a heavy garment,
finding someone who doesn't like you very much. and having him strap the plate onto you, molding it to an exact fit. This method is only moderately painful. (Make sure that you really don't like the clothing very much. No matter what you do, you
will always have a ghost image of your harness.)
Addendum
I. Do all of your cutting, and punch any rivet holes before hardening the leather.
This is armor: it was intended to be
hard to cut.
2. If the harness becomes deformed by being crammed into a car trunk for several
hours, you can usually repair it by laying it on a dark cloth in the sun for
about half an hour. It will become just barely pliable enough and from there
can be fitted back onto your person.
3. Don't attach straps to your harness until after you have hardened it. Wax will get into the thin leather and make it just stiff enough to be maddeningly uncomfortable.
4. Couir Boulli is an ideal medium for other craftsmen. The Metropolitan Museum has many cups, cases, and
chests made from hardened leather.
S. Couir Boulli is ideal for articulated armor. This style uses square or rectangular plates riveted or sewn to a leather or
canvas tunic, in a brickwork pattern. This armor is most effective if you use very thick plates and cut the edges to a good right angle. The plates will lock, and become very rigid when struck.
John L. Henry, Jr. 1997 Macon Georgia for the SCA of Warner-Robbins