What is goldbeaters’ skin?

Goldbeaters’ skin is a fine membrane made of the outer coat of the blind gut in cattle and is used by goldbeaters to separate the leaves of metal during the last and most difficult stages of hammering out gold leaf. The intestine, after being put through several processes, is cut into pieces about five inches square. Its tenacity and powers of resistance are so great that it will resist the continous pounding of a heavy hammer for several months. Goldbeaters still do their work by hand as they did in ancient times. A large number of leaves are beaten at the same time and hammers ranging in weight from seven to twenty pounds are used. Gold is the most malleable of all metals and the minimum thickness to which it can be beaten with patience and skill is not known for certain. It is said that an ounce of pure gold can be beaten into enough gold leaf to cover an acre. A single grain of gold has been beaten into a leaf having an area of seventy-five square inches and a thickness of less than 1/368,000 of an inch. Commercial gold leaf ranges from 1/200,000 to 1/250,000 of an inch in thickness.