The Manuscript Codex * Materials
LEATHER

The outer layer of an animal skin, usually a domestic species such as goat, sheep or cow, which is tanned or tawed to make it strong, durable and resistant to biological degradation. The principal component of leather is an interlocking three-dimensional network of fibers of collagen, a type of protein. The skin of an animal is cleaned, scraped and de-haired and then soaked in a series of solutions, some of which contain tannin. Historically a variety of vegetal materials were used as tannin sources. During the tanning process, the protein molecules in the leather become more durable and resistant to microbiological attack and turn a brown color.
# Technically, alum-tawed skin is not leather, as alum-tawing is a different chemical process that leaves the skin still vulnerable to decay in wet conditions. However, alum-tawed skin is not infrequently referred to as leather, especially when it has not been clearly identified.
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AUTHORS: PAUL HEPWORTH AND KARIN SCHEPER