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Preparation of Foils

Foils are thin plates or leaves of metal that are put under stones, or compositions in imitation of stones, when they are set.

The intention of foils is either to increase the lustre or play of the stones, or more generally to improve the color, by giving an additional force to the tinge, whether it be natural or artificial, by that of a ground of the same hue, which the foil is in this case made to be.

There are consequently two kinds of foils; the one is colorless, where the effect of giving lustre or play to the stone is produced by the polish of the surface, which makes it act as a mirror, and, by reflecting the light, prevents that deadness which attends the having a duller ground under the stone, and brings it by the double refraction of the light that is caused, nearer to the effect of the diamond. The other is colored with some pigment or stain of the same hue as the stone, or of some other which is intended to modify and change the hue of the stone in some degree; as, where a yellow foil may be put under green, which is too which can only be done, in a perfect manner, by the use of quicksilver, applied in the same general by which it may be best performed is as follows: way as in the case of looking-glasses. The method Take leaves of tin, prepared in the same maninto small pieces of such size as to cover the surner as for silvering looking-glasses, and cut them face of the sockets or the stones that are to be set. set. Lay three of these then, one upon another, and having moistened the inside of the socket with thin gum-water, and suffered it to become put the three pieces of leaves, lying on each other, again so dry that only a slight stickiness remains, into it, and adapt them to the surface in as even the socket and fill it with warm quicksilver, which a manner as possible. When this is done, heat must be suffered to continue in it 3 or 4 minutes, and then gently poured out. The stone must then be thrust into the socket, and closed with it, that it may enter without stripping off the tin and care having been taken to give such room for it quicksilver from any part of the furnace. The work should be well closed round the stone, to prevent the tin and quicksilver contained in the socket from being shaken out by any violence.

The lustre of stones set in this manner will con- | amethyst, topaz, vinegar-garnet and eagle-ma. tinue longer than when they are set in the common way, as, the cavity round them being filled, being filled , there will be no passage found for moisture, which is SO injurious to the wear of stones treated in any other way.

This kind of foil likewise gives some lustre to glass or other transparent matter, which has little of itself; but to stones or pastes that have some share of play it gives a most beautiful brilliance.

To Color Foils.

Two methods have been invented for coloring foils the one by tingeing the surface of the copper of the color required by means of smoke, the other by staining or painting it with some pigment or other coloring substance. coloring substance.

The colors used for painting foils may be tempered with either oil, water rendered duly viscid by gum Arabic, size or varnish. Where deep codeep colors are wanted, oil is most proper, because some , because some pigments become wholly transparent in it, as lake , or Prussian blue; but yellow and green may be better laid on in varnish, as these colors may be had in perfection from a tinge wholly dissolved in spirit of wine, in the same manner as in the case of lacquers, and the most beautiful green is to be produced by distilled verdigris, which is apt to lose its color and turn black with oil. In common cases, however, any of the colors may be, with least trouble, laid on with isinglass size. in the same manner as the glazing colors used in miniacolors used in ture painting.

Ruby Colors.

For red, where the ruby is to be imitated, carmine, a little lake used in isinglass size, or shellac varnish is to be employed, if the glass or paste be of a full crimson, verging towards the purple; but if the glass incline to the scarlet or orange, very bright lake (that is, not purple) may be used alone in oil.

Garnet Red.

For the garnet red, dragon's blood dissolved in seed-lac varnish may be used; and for the vinegar garnet, the orange lake, tempered with shellac varnish, will be found excellent.

Amethyst.

For the amethyst, lake, with a little Prussian blue, used with oil, and very thinly spread on the foil, will completely answer the end.

Blue.

For blue, where a deep color, or the effect of the sapphire is wanted, Prussian blue, that is not too deep, should be used in oil, and it should be spread more or less thinly on the foil, according to the lightness or deepness of which the color is required to be.

Eagle Marine.

For the eagle marine, common verdigris with a little Prussian blue, tempered in shellac varnish, may be used.

Yellow.

Where a full yellow is desired, the foil may be colored with yellow lacquer, laid on as for other purposes; and for the slighter color of topazes the burnish and foil itself will be sufficiently strong without any addition.

Green.

For green, where a deep hue is required, the crystals of verdigris, tempered in shellac varnish, should be used, but where the emerald is to be imitated, a little yellow lacquer should be added to bring the color to a truer green, and less vergless verging to the blue. Other Colors. rine, may be very cheaply imitated by transparent white glass or paste, even without foils. This is to be done by tempering the colors above enumerated with turpentine and mastic, and paint- , and painting the socket in which the counterfeit stone is to be set with the mixture, the socket and stone itstone itself being previously heated. In this case, howcase, however, the stone should be immediately set, and the socket closed upon it before the mixture cools and grows hard. The orange lake above menlake above mentioned was invented for this purpose, in which it has a beautiful effect, and was used with great success by a considerable manufacturer. The color it produces is that of the vinegar-garnet, which it affords with great brightness. The colors be- . The colors before directed to be used in oil should be extremely well ground in oil of turpentine, and tempered with old nut or poppy-oil; or, if time can be given for the drying, with strong fat oil diluted with spirit of turpentine, which will gain a fine polish of itself.

The colors used in varnish should be likewise thoroughly well ground and mixed; and, in the case of the dragon's blood in the seed-lac varnish and the lacquer, the foils should be warmed before they are laid out. All the mixtures should be laid on the foils with a broad, soft brush, which must be passed from one end to the other, and no part should be crossed or twice gone over, or, at least, not till the first coat can be dry; when, if the color do not lie strong enough, a second coat may be given.