![]() Backup rolls mounted above the work rolls of the finishing mills provide increased vertical pressure. The reduction of sheet metal to foil is achieved principally through vertical pressure exerted by finishing-mill rolls combined with horizontal tension applied through mandrels paying out and rewinding the foil stock. The first mass-produced and widely used foil was made from tin, now replaced by aluminum for nearly all purposes. The colour and lustre of the gems is heightened by foil that has been silvered, burnished and coated with translucent colouring. ![]() ![]() Jewellers have long used a thin foil of copper-zinc alloy as backing for paste jewels and inferior gemstones. solid metal that has been reduced to a leaflike thinness by mechanical beating or rolling.
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