tawing ( tawed "leather" )
An ancient process of treating prepared hide or
skin (usually pigskin or goatskin) with aluminum
salts and (usually) other materials, such as egg
yolk, flour, salt, etc. A skin may actually be
tawed simply by immersing it in an aqueous
solution of potash alum at a temperature between
20 and 30° C; however, salt is usually
included in the alum solution because it improves
the substance (thickness) of the final product.
After treatment the skin is dried in air (crusted)
and held in this condition for several weeks to
allow the development of stabilization or "aging"
effects. Tawed skins also undergo STAKING to impart of
soft, flexible handle. Apart from this soft, warm
handle, the tawed skins have a high degree of
stretch. Handle and stretch may also be improved
by the addition of egg yolk and flour to the basic
alum and salt solution. A tawed skin is usually
white in color but may yellow slightly with age.
Tawing does not actually produce a skin that is
stable in the wet condition, i.e., imputrescible
in the wet state, and therefore cannot accurately
be described as having been tanned; consequently,
in a strict sense, a tawed skin is not leather.
(61 , 237 , 291 )