Goldbeater's skin
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Goldbeater's skin — the outer membrane of calf's intestine — is a parchment traditionally used in the process of reducing gold into mere 1μm-thick leaves. Up to 120 sheets of gold laminated with goldbeater's skin can be beaten at the same time, since the skin is thin, elastic and does not tear under heavy goldbeating.
It is used as the sensitive element in hygrometers since due to its hygroscopic property, variations in atmospheric humidity cause skin contraction or expansion. Alexander Graham Bell used a drum of goldbeater's skin with an armature of magnetised iron attached to its middle as a 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 these high-value stamps. Joseph Thomas Clover invented an apparatus for the inhalation of chloroform in 1862. This consisted of a large reservoir bag lined with goldbeater's skin to make it airtight, into which a known volume of liquid chloroform was injected[1].
Due to its transparency, strength and fairly uniform thickness goldbeater's skin is also used in conservation of manuscripts written on vellum to repair holes and vellum tears. To manufacture goldbeater's skin the gut of oxen (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
- ^ Sykes WS (1960). Essays on the First Hundred Years of Anaesthesia, Vol. 2, Churchill Livingstone, Edinburgh. ISBN 0 443 02866 4, p. 8.
- 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
