BLANCHING, in coinage, the operation performed on the planchets, or pieces of silver, to give them the requisite lustre and brightness. They also blanch pieces of plate, when they would have them continue white, or have only some parts of them burnished. Blanching, as it is now practised, is performed by heating the pieces on a kind of peel with a wood fire, in the manner of a reverberatory; so that the flame passes over the peel. The pieces being sufficiently heated and cooled again, are put successively to boil in two pans, which are of copper: in these they put water, common salt,
Blanching salt, and tartar of Montpellier. When they have been well drained of this water in a copper sieve, they throw sand and fresh water over them; and when dry, they are well rubbed with towels.