Goldbeater's skin

Goldbeater's skin—the outer membrane of a calf's intestine—is a parchment traditionally used in the process of making gold leaf by beating, reducing gold into mere 1 μm-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 one inch thick.

Uses

Goldbeater's skin 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 that 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.

Large quantities of goldbeater's skin were used to make the gas bags of early balloons created by the Royal Engineers at Chatham, Kent starting in 1881–82 culminating in 1883 with "The Heron", of 10,000 cu ft capacity. The method of preparing and making gas-tight joins in the skins was known only to a family from Alsatia called Weinling who were employed by the RE for many years. The British had a monopoly on the technique until around 1912 when the Germans adopted the material for the internal gas bags of the "Zeppelin" rigid airships, exhausting the available supply: about 200,000 sheets were used for a typical World War I 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 goldbeater's skin test is used to assess the tanning properties of a compound.

See also

Vark

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. 1 2 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

External links

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