LEATHERWORKING

There are three methods of making leather: oiling, tawing and tanning. Oiling is the simplest method and involves working animal fat into the skins and then curing them with smoke. This acts a preservative and produces a buff-coloured product. This method is already falling out of favour by the medieval period.

In tawing, the skins are first soaked in water to soften them, then the skin and hair are scraped off with a concave 'scudding knife'. The skins are then dipped in a vat of alum water. The exact composition of this solution determines the quality of the result; the best mixtures contain alum, salt, egg yolk, flour and oil. The leather is hung up to dry, dampened again (fermented bran is used here to make the highest quality leathers) and then beaten with mallets to soften it, before being staked out ready for use. Tawing produces white leather.

If especially soft leather is required (e.g. for making bags) the skins can be soaked in vats of warm dog manure until they are soft to the touch. Cold chicken droppings can be used as an alternative.

A variant method of tawing involves sponging the alum water onto the inside of the leather rather than steeping in a vat. This leaves the fur on the outside of the leather.

Tanning is similar to tawing, but replaces the alum water with vats of increasingly fresh, and therefore concentrated, oak bark extract. The leathers are then laid in a liquor pit separated by crushed bark. The powdered leaves of certain tropical plants are superior to oak bark, and replace it if they are available. The whole process takes anything up to fifteen months, and produces high quality leather in varying shades of brown. It can be coloured by adding vegetable or mineral dyes.

Water-powered automation made relatively little inroad into tanning compared with many other industries in the Renaissance. However, some machines were developed for beating out the skins.

PARCHMENT

Parchment is the usual substrate for writing in the medieval period, although paper becomes more popular later on. Parchment is usually made from calf or goat skin. The skins are washed and then placed in a tub of cold water for a day. They are then smeared with slaked lime paste and left for a week in a warm environment. The hair is then scraped off with a scudding knife, and the process is repeated with fresh lime. The skins are then washed again, stretched on a frame, washed in even colder water, partially dryed and washed a fourth time. After all of this, the leather is scudded down to the requisite thickness - an extremely delicate operation. Finally, they are rubbed smooth with pumice and dried and stretched out ready for use.

CUIRBOILLI

To make moulded leather, high quality tanned leather is soaked in water until it becomes soft and pliable. It can then be moulded into an appropriate shape and dried out until it hardens again. This is commonly used to make coverings for chairs or chests in the Renaissance era. The higher the temperature at which the leather is dried, the harder the resulting product. Generally, little if any heat is required, but to make leather armour, the moulded suit is dipped briefly into boiling water or oil. The result is substantially harder than normal leather.