of calico, and revolved by gearing in opposite directions. As a last precaution, before being finally wound on the spools, the wire is completely dried by passing it through a large flat tube, L, maintained at a dull red heat in the furnace I.

In a bath of the size indicated above, twenty coils may be gilded at the same time. The copper wire to be gilded is generally silvered beforehand, and passed once through a draw-plate, in order to avoid the cleansing process before gilding.

The more intense the current, or the slower the rate of passage of the wire through the bath, the greater will be the quantity of gold deposited; and to make no mistakes, it will be well to weigh the bobbins before and after the operation. For this purpose, the extreme spools for paying out and winding should be of the same weight.

This process of gilding requires constant supervision, either for uniting the broken ends, the severed parts of which may touch the anodes and stop the operation; or for regulating the intensity of the current, which, if too powerful or too weak, will produce, correspondingly, a red or green gilding.

The baths of double cyanide of gold and potassium are employed cold or slightly tepid (Chapter XX.).

On the other hand, the baths with phosphate and bisulphite of sodium are used for hot electro-gilding, and their concentration should be double, i. e., the proportion of water should be one-half of that indicated (Chapter XXI.).

As the platinum anodes do not make up for the metallic loss of the bath, it is necessary to add frequently new portions of metal and of solvents, in the manner already indicated.

Pure gold wire is often gilded, in order to impart to it a more uniform, and a deeper shade.

After being gilded, the wire is passed through the drawplate or rollers, according as we desire to have it round. or flat. With the draw-plate it is diminished by about one-fourth or one-half of a number, simply to remove the dulness of the deposit, and bring up the lustre. When the gilded wire is flattened between rollers, its surface is bright or dull, according to the condition of the surface of the rollers.

It is evident that silvering, or any other metallic electro-deposit, may be effected upon fine wire in a similar

manner.

WHEN We desire to obtain upon the same object gild ings of several colors, we employ "stopping-off" varnishes. Thus, after having gilded an article of a uniform color (red, or green, for instance), it is covered with a fatty varnish (made drying by the addition of chromate of lead), at those places which we desire to preserve from, or to resist the action of, the new bath. By thus "stoppingoff," and using successive baths, we are enabled to obtain five or six different shades upon the same object.

The "stopping-off" varnishes are applied with a brush or pencil, and should be thoroughly dried in a stove before the object is introduced into another solution. These varnishes may be colored with various oxides, or colored salts, in order to facilitate their use upon those places which should be sharply delineated; chromate of lead

and artificial ultramarine blue, are well suited for the purpose. The "stopping-off" varnishes are also employed for protecting the reverse parts of articles which are intended to receive the gilding only on one side. When the operation is finished, the varnish is easily removed by a washing, first with essence of turpentine, and then with alcohol. These liquids may be advantageously replaced by gasoline, benzine, or benzole. The latter substance is a product of the distillation of coal-tar, and dissolves, even in the cold, nearly all fatty and resinous bodies. It is sufficient, when we have used benzole, to wash the article in boiling water, and then to dry it in warm sawdust, from which it comes out perfectly clean. Such is not always the case with rectified turpentine, and it is prudent, where this has been used, to plunge the object afterwards into a hot lye of caustic potash, then to rinse and dry it in warm sawdust. We describe these varnishes more fully in another chapter.

CHAPTER XXV.

DEAD-GILDING-FIRE-GILDING-GILDING, PARTLY DEAD, PARTLY BRIGHT (DEMI-MATT).

Dead-Gilding.

In addition to the several processes previously indicated, dead-lustre gilding may be obtained by a number of different methods.

1. By the slow deposit of a large quantity of gold. This gilding is very durable, but is dull and earthy in appearance. Moreover it is too costly for the arts.

2. By acids; that is to say, by giving a dead lustre to

the metallic surface, before gilding, and by the processes indicated in the cleansing operations. This method is employed only for small articles, or when gilding by immersion. Varnishers, however, use it for bronze articles, or large embossed work.

3. With frosted silver, i. e., by depositing upon the ob ject to be gilded, a coating of frosted silver (by processes soon to be described), and then gilding in a good bath. Unfortunately, this method is somewhat expensive, and the burnished parts are greenish. Moreover the interme diary coat of silver is easily affected by sulphurous gases, and the gilding is thus blackened.

4. By copper, i. e., by depositing in a solution of sulphate of copper, decomposed by the current, a galvanoplastic coat of this metal which possesses a pink, dead lustre. The piece is then rapidly passed through the acid mixture for bright dipping, then through quicking solution, and finally gilded in a good bath. When the dead lustre obtained in the galvanoplastic bath is perfect, the subsequent use of the acids may be dispensed with, and the article is simply plunged into the quicking solution before gilding. This last mode of operation is generally preferred by gilders. This gilding is very handsome in lustre and color. The burnished parts will be red, if vinegar or soap-water be employed; and of a fine yellow color, if the burnish be wetted with saliva, a decoction of flaxseed, of soapwort, or of marshmallow root. We shall indicate further on the best conditions for obtaining a fine dead lustre with copper.

If the deposit of gold be of insufficient thickness, it will blacken sooner or later, by the oxidization of the interme diary coat of copper.

5. Lastly, dead lustre may be effected with the aid of mercury. This is the old process of gilding by fire, which

we shall now describe.

It furnishes the most durable

products, but the method is costly.

Fire-Gilding.

Although we have chosen this chapter on dead-lustre gilding for describing the method of fire-gilding, it should not be forgotten that we may also produce a bright lustre by the same means. Before the introduction of the galvanic processes into the arts, there were nearly as many sorts of gildings as at the present time; but their cost was greater, the operations were more difficult, and the workman was constantly exposed to the deleterious vapors of mercury. We must also acknowledge that the products were, and still are, superior in respect to durability, if not in appearance to those obtained by electro-deposition.

Fire-gilding may furnish gilding with a bright or a dead lustre, scratch-brushed, ormolued, and also with different shades. We indicate in the following, the different modes of operation.

The amalgam of gold is prepared in the manner described in the process of gilding with amalgam (Chapter XVII.). only a little less mercury is used, in order to obtain an amalgam about as hard as wax. This amalgam is crystalline, and a certain crackling sound is heard when we press the crystals between the fingers. A stock of amalgam is generally prepared in advance, and it is divided into small pellets of nearly equal size, the value of which is ascertained from their number, and from the total weight of gold employed. Thus, if 100 grains of gold has been used, and the resulting amalgam has been divided into ten equal pellets, each one will contain 10 grains of the precious metal. These pellets are kept in water, but they should not remain too long without being used, because the phenomenon of liquation takes place,