From: cav@bmerh364.BNR.CA (Rick Cavasin) Subject: Re: Cariadoc's query (hardened leather) Date: 11 Dec 91 13:49:20 GMT Organization: Bell-Northern Research Ltd. Unto Duke Sir Cariadoc does Lord Balderik sent his greetings. Below I have given a brief note on cuir boulli I once prepared as a Rialto posting but never got around to posting until the thread had petered out. I hope it may be of some use. If you would like more info, feel free to contact me via the Rialto (I do not have external E-mail). According to Waterer (Leather Craftmanship, Leather and the Warrior, etc.), the cuir boulli effect is obtained when vegetable tanned leather is dried at elevated temperatures. It is a chemical reaction which converts the leather into something more closely resembling plastic (I forget the details). It will only occur with vegetable tanned leather (the stuff used for tooling leather). The temperature is critical: too low and no hardening occurs, too high and the leather becomes brittle. R. Reid (or was it Reed? in his book Ancient Skins, Parchments, and Leathers) concurrs, adding that it was also achieved by briefly (!) dipping the leather in boiling water for between 20 and 120 sec. I have yet to experiment with this technique. The application of wax is not necessary, although it enhances the effect by increasing the density of the leather and limiting the softening that can occur when the leather is dampened (the use of a wax hardener as mentioned in a previous posting will achieve a similar effect no doubt!). The wax also makes the leather tougher. I do not recall either Waterer or Reed making mention of the use of wax for cuir boulli armour, but I would have to check. I made cuir boulli arm harness' as follows: 1) cut out individual lames from leather 2) select forms on which leather will be dried : -lames were tied onto coffee cans with string (don't use tape!!!) -vambraces were tied onto newspapers which were rolled up into roughly conical shapes 3) in order to determine the optimum temperature, the scrap bits of leather were used to experiment with different oven settings (soak piece of leather in water until saturated, dry in oven, check result) 4) when the correct setting for the oven in question is determined, the individual armour components (not yet assembled) are soaked in water until saturated, and then tied firmly to their respective forms (note that if you are ambitious you can carve positive and negative molds in order to impress decorations in relief on the armour - very period! - see Waterer). 5) place forms in oven and prop door open a crack to let the moisture escape. 6) melt some parafin wax (beeswax can be used but it is expensive and will smell like honey when your armour is in the sun for a while) in a double boiler (a bowl sitting in a pot of boiling water works). 7) when the pieces are dry and hardened, remove them from the forms (careful of heat) and brush on the molten wax with a basting brush or some such implement. Pieces can be returned to the oven (placed on a cookie sheet or some such) in order to allow the wax to permiate the leather. The oven should be hot enough to melt the wax, but NOT hot enough to burn it! EXERCISE DUE CAUTION! SEE INSTRUCTIONS IN EARLIER POSTINGS ON WAXING ARMOUR. 8) When the pieces are hardened and waxed, any rivet holes needed (unless prepunched) can be drilled. Edges can be filed/sanded. An old fashioned (period?) method for hardening shoe soles (if they are made of vegetable tanned leather) is to soak and HAMMER them. The compression/heat of hammering probably produces an effect analagous to that of cuir boulli. It has the advantage of stretching and consolidating the leather to limit changes in the sole's shape once the shoe starts being worn. Given the similarities between the two applications, I thought it natural to wax the soles of my boots in the same way as my armour. The soles get harder, tougher, and less succeptable to dampness. They can however be very slippery the first time you wear them so it is best to go out on the pavement and scuff them up a bit before dancing on a hardwood floor! Hope this helps, Balderick (of pathless wastes fame) These are not the opinions of my employer.