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animal parchment has been used since the seventeenth century; also vegetable parchment in the later stages. Comparative experiments have shown that animal parchment permits only a relatively very slight reduction of the metal sheet; parchment paper allows the metal to be beaten somewhat thinner, but when the linfit is passed the metal adheres so firmly to the paper that it cannot be separated without damage. According to a process devised by J. Heinrich (Ger. Pat. I23,I97 ), thin, tough paper of substance of 25 to 3o grammes per square metre is steeped in a hot solution of borax or alum. The paper is stretched over frames, and a coating, first of albumin and then of isinglass solution, is applied, first to one side and then to the other. Papers of various kinds are now used in many goldbeaters' shops, but only for the first stages; the leaf metal is always finished between ordinary goHbeaters' skin Leaf made from baser metals, however, is beaten throughout between paper. A papr which will serve all the purposes of skin for the manufacture of gold-leaf has yet to be discovered.
Corrosion of Iron Machinery. .ANON. (SCi.
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