Goldbeater's skin
From Wikipedia, the free encyclopedia
Goldbeater's skin — the outer membrane of calf's intestine — is parchment material traditionally used in the process of reducing gold into mere 1μm-thick leaves. Up to 120 sheets of gold laminated with goldbeater's skin could be beaten at one time since skin is thin, elastic and did not tear under heavy goldbeating.
It is used as sensitive element in hygrometers since due it hygroscopic property variations in atmospheric humidity causes skin contraction or expansion. Alexander Graham Bell used drum of goldbeater's skin with an armature of magnetised iron attached to its middle as sound receiver (see Invention of the telephone) and the North German Confederation printed 10- and 30-groschen postage stamps on goldbeater's skin, to prevent reuse of the high-value stamps.
Due to its transparency, strength and fairly uniform thickness goldbeater's skin is also used in conservation of the manuscripts written on vellum to repair holes and vellum tears. To manufacture goldbeater's skin the gut of ox (or other cattle) is soaked in a dilute solution of potassium hydroxide, washed, stretched, beaten flat and thin, and treated chemically to prevent putrefaction. A pack of 1,000 pieces of goldbeater's skin requires the gut of about 400 oxen, and is only 1 inch thick.
[edit] References
- Notes on the Manufacture of Goldbeater's Skin by Jack C. Thompson
- Bookbinding and the Conservation of Books. Goldbeater's skin.
- The History and Biology of Parchment by Robert Fuchs
