FOIL. A general name for thin metal inter mediate in thickness between /co/ porto/, such as gold. silver, and copper 'leaf, and shi•ct metal. There are t WO distinct kinds of foil in common use: The very thin tinfoil used in chemistry. for electrical apparatus, and formerly for coating the backs of mirrors (q.v.) ; and the brighter, thicker foils, which, under the name of 'tinsel; are made of copper, tin, tinned copper. or sil vered copper, and are used by jewelers for theati'ical and other ornaments. The foils used by jewelers for backing sometimes called Dutch foils, consisting of small sheets of silvered copper rolled very thin. are colored with the fol lowing preparations, to suit the different gems under which they arc to be placed. or for use as tinsel in the manufacture of t heat Heat ornaments. toys, etc.: Lake and Prussian blue. and pale drying-oil finely ground with a slab and mullar for amethyst color. Prussian blue similarly prepared—fo• sapphire color. Dragons' blood dissolved in pure alcohol—for garnet color. Fer roeyanide of iron and bichromate of potash, equal parts, very finely ground and sifted, then ground with a quantity of gum mastic equal to the other two ingredients, until the whole forms an impalpable powder; gradually form this into a thin paste with pure wood alcohol and preserve in a stoppered bottle; \\•ien used, a por tion is diluted with wood alcohol to the neces sary thinness—for emerald color. Various shades
of yellowish or bluish green can be produced by varying the proportions of the two coloring ma terials. Lake or carmine ground in solution of isinglass—for ruby color. A weak solution of orange shellac, sometimes tinted with saffron, turmeric, or aloes—for topaz color. Several other color-varnishes are made by similar methods for various shades of tinsel and gem foils.
Gold foil is chiefly used by dentists for filling teeth, and differs from gold leaf only in being a little thicker. (See GOLD-BEATING.) Com mercial tinfoil is largely adulterated with lead, and is used as a wrapping for tobacco, chocolates, and bonbons, toilet and other fancy articles. Variegated foil is made by laying thirty or forty thin plates of gold, silver, copper. and various alloys in a regular order. and then soldering the edges. A pattern of various depths is punched, and the metal hammered out into a thin sheet. The punch-marks disappear, and the pattern, ap pearing sometimes in one and sometimes in an other of the metals, and much spread out, is very effective. It is suggestive of damaskeening on metal. See DAMASKEENING.
FOIL (prol.ahly from foil, to blunt, from OF. fouler, foler, Niter, Fr. fou/cr, to trample, from fullare, to full cloth by trampling, from Lat. hullo, fuller). A weapon used in fencing as a :substitute for the short sword. See FENCING.