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.

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] Uses

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 to repair holes and tears in manuscripts written on vellum.

In the early 1900s large quantities of goldbeater's skin were used to make the gas bags of rigid airships, exhausting the available supply: about 200,000 sheets for a typical World War 1 Zeppelin, while the USS Shenandoah needed 750,000 sheets.[2] The sheets were joined together and folded into impermeable layers.[2]

Goldbeater's skin (sometimes also called "fish skin" in this context) is sometimes also used to seal oboe reeds, to prevent them from leaking air.[3]

The gold beater skin test is used to assess the tanning properties of a compound (when gold beater skin or ox skin is dipped in HCl & treated with 1% FeSO4 solution, after washing with water it gives a blue / black colour).

[edit] References

  1. ^ Sykes WS (1960). Essays on the First Hundred Years of Anaesthesia, Vol. 2, Churchill Livingstone, Edinburgh. ISBN 0 443 02866 4, p. 8.
  2. ^ a b Steadman, Mark (2006-05-01). "The Goldbeater, the Cow and the Airship". Post & Tele Museum, Denmark. Retrieved 2009-09-12. 
  3. ^ Goldbeaters' skin for Oboe - large - Oboe Reed-making - Britannia Reeds

[edit] External links

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