The principal object in fine casting is to have a mould that shall receive a beautiful impression, and at the same time sufficiently adhesive to resist the force of the fluid metal, that shall neither wash nor be injured by the heat. The sand that covers or surrounds the model should be fine, close sand; after removing the mould, the model must be faced with burnt rotten-stone, and covered with loam, each dusted through a bag, and the mould laid down upon it; this facing may be repeated, the mould must be dried and smoked with a torch; in lieu of water, the sand is moistened with a solution of tartar, or the lees of wine, or with cream of tartar. Care must be taken to loosen the band quickly, viz.: loosen the first mould while the second is pouring, etc. On removing the work, every particle of the facing should be carefully scraped from the mould and thrown away. Part the moulds with coal and black rosin.
Melt together 4 parts of copper, 1 of Bristol old brass and 14 oz. of tin to every lb. of copper.
_For Common Jewelry._
Melt together 3 parts of copper, 1 of Bristol old brass and 4 oz. of tin to every lb. of copper.
If this alloy is for fine publishing, the tin maybe omitted, and a mixture of lead and antimony substituted. Paler polishing metal is made by reducing the copper to two or to one part.
Melt together 2 parts of brass, 1 part of copper, with a little old brass, and 1/4 oz. of tin to every lb. of copper. This alloy is almost of the color, etc., of gold coin.
Another.--Good dipping-metal may be made of 1 lb. of copper to 5 oz. of spelter; the copper should be tough cake, and not tile.
When antinomy is used instead of tin, it should be in smaller quantity, or the metal will be brittle.
_Imitation of Silver._
When copper is melted with tin, about 3/4 oz. of tin to 1 lb. of copper, will make a pale bell metal; it will roll and ring very near to sterling silver.
_Tutania or Britannia Metal._
Melt together 4 oz. of plate-brass and 4 oz. tin. When in fusion, add 4 oz. bismuth and 4 oz. regulus of antimony.
This is the hardening, which is to be added at discretion to melted tin, until it has the requisite color and hardness.
Another,--Melt together 2 lbs. of plate-brass, 2 lbs. of a mixture of copper and arsenic, either by cementing or melting, 2 lbs. of tin, 2 lbs. of bismuth and 2 lbs. regulus of antimony.
This is to be added at discretion to melted tin.
Another.--Melt together 1 lb. of copper, 1 lb. tin and 2 lbs. regulus of antimony, with or without a little bismuth.
Another.--Melt together 8 oz. Shruff brass, 2 lbs. regulus of antimony and 10 lbs. tin.
This is fit for use as Britannia metal.
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