alum-tawed skin

A skin prepared in an aqueous solution of a double salt of aluminium and potassium sulphates. The process, which is of great antiquity, produces a white skin which is dried (crusted) and then staked, or worked over a blunt metal knife, to produce a soft, supple skin, qualities which could be enhanced by the addition of flour and egg-yolk to the tawing solution. If wetted again, as many blind-tooled German bindings of the late fifteenth to the mid-eighteenth century were before tooling, the skin becomes once more hard and horny, as though it had reverted to the raw, untanned state. Also known as tawed skin (Reed, pp.62-65).

Reed (1972)

Reed, R., 1972. Ancient Skins, Parchments and Leathers, London: Seminar Press.

Additional reference: 
pp. 62-65

Middleton (1994, 4th ed.)

Bernard Middleton, A history of English Craft Bookbinding Techniques, New Castle, London, Oak Knoll Press, The British Library, 1994 (4th ed.)

Additional reference: 
p. 117
Alternative label: 
tawed
white leather
white tawed
whittawed
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