FOLIATING of LOOKING-GLASSES, the spreading the plates over, after they are polished, with quicksilver, &c. in order to reflect the image. It is performed thus: A thin blotting paper is spread on the table, and sprinkled with fine chalk; and then a fine lamina or leaf of tin, called foil, is laid over the paper; upon this is poured mercury, which is to be distributed equally over the leaf with a hare's-foot or cotton: over this is laid a clean paper, and over that the glass-plate, which is pressed down with the right-hand, and the paper drawn gently out with the left: this being done, the plate is covered with a thicker paper, and loaded with a greater weight, that the superfluous mercury may be driven out and the tin adhered more closely to the glass. When it is dried, the weight is removed, and the looking-glass is complete.
Some add an ounce of marcasite, melted by the fire; and, lest the mercury should evaporate in smoke, they pour it into cold water; and when cooled, squeeze through a cloth, or through leather.
Some add a quarter of an ounce of tin and lead to the marcasite, that the glass may dry the sooner.