This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
The metal plate is laid between parchment leaves and beaten out with hammers. Although films obtained in this manner reach a high degree of fineness, yet the mechanical production has its limit. If very fine films are desired the galvano-plastic precipitation is employed in the following manner:
A thin sheet of polished copper is entered in the bath and connected with the electric conduit. The current precipitates gold on it. In order to loosen it, the gilt copper plate is placed in a solution of ferric chloride, which dissolves the copper and leaves the gold behind. In this manner gold leaf can be hammered out to almost incredible thinness.
Tin foil is the most common foil used, being a combination of tin, lead, and copper, sometimes with properties of other metals.
I | II | III | |
Per cent | Per cent | Per cent | |
Tin...... | . . 97.60 | 98.47 | 96.21 |
Copper. , Lead..... | .. 2.11 | 0.38 | 0.95 |
. . 0.04 | 0.84 | 2.41 | |
0.11 | 0.12 | 0.09 | |
Nickel.. .. | 0.30 |
I is a mirror foil; III is a tin foil.
Tin........ | I Per cent ..... 20 | II Per cent 22 |
Copper..... | ., 80 | 77 1 |
I II | III | |
Per cent Per cent | Per cent | |
Tin...... | 97 90 | 92 |
2.5 7.8 | 7 | |
Copper.. . | 0.5 0.2 | 1 |
I | II III | |
Per cent | Per cent Per cent | |
Tin...... | 60 | 65 40 |
40 | 35 58.5 | |
Copper.. | 1.5 |
 
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