sawdust, bran, or sand, into a cloth sack about 4 feet in length; then, the ends being gathered into the hands with the thumbs inwards, a regular motion with both arms from right to left and from left to right is given to the bag, so that one of its extremities is alternately raised while the other is lowered. The inclosed articles must follow this motion, and by rolling over each other become gradually polished.

When it is deemed preferable to perform this operation in water, which is frequently the case, a device like that shown in Fig. 26 is found to be very serviceable. It con

Fig. 26.

sists of a small tub suspended by long cords to a beam. of the ceiling, to which the operator imparts a to-andfro motion whereby the articles to be polished are made to roll one over the other.

Another apparatus for cleaning by attrition, is the tumbling-box shown in Fig. 27. It consists of a cylindrical or polygonal box, having a side door for the introduction of the work, and is mounted horizontally on

Fig. 27.

an axis furnished with a winch or pulley, so as to be revolved either by hand or power as may be desired. —In order to prevent certain objects, like hooks for ladies' dresses and the like, from catching each other and accumulating into a mass, a number of nails or wooden pegs are fixed in the interior of the drum.

CHAPTER VI.

GOLD-VARNISH.

ALTHOUGH, strictly speaking, this work should be confined to subjects relating to the deposition of metals, we assume that most of our readers will be interested in a description of those processes by which those magnificent varnishes are obtained which imitate so completely the appearance, freshness, and rich tones of real gilding. In

general, varnish is applied only upon copper and its more or less yellow alloys.

Gold varnishers operate as follows: After the pieces have been perfectly cleansed, scratch-brushed, and burnished if necessary, they are completely dried in the hot sawdust, and wiped clean with a fine cloth. A light coat of varnish is then applied with a fitch-pencil, and all excess of varnish removed or levelled with another flat brush of badger-hair or bristles. The two brushes are kept together in the same hand, the varnish brush between the thumb and first two fingers, while the flat one (without a handle) is held between the other fingers and the palm of the hand. (Fig. 28.)

Fig. 28.

In this manner there is no interval in the use of the two brushes. The varnish is kept in a jelly-pot or other

similar vessel, across the top of which a string has been stretched. This string is intended for removing, by wiping, the excess of varnish taken up by the brush or pencil. (Fig. 29.)

Fig. 29.

The varnish which covers the burnished parts of the piece may be removed with a clean rag wetted in alcohol and wrapped around the finger. Another dry cloth finishes the drying. Sometimes the burnished parts are also varnished, but the operation is very difficult when their surface is considerable. Round wares, polished or burnished, may be varnished in the lathe.

After the varnish has been applied as uniformly as possible, the wares are put into a drying stove heated from about 140° to 175° Fah., or supported upon wires on top of a small furnace heated with smouldering charcoal-dust. The alcohol or essential oils of the varnish are rapidly volatilized, while the resins or gums melt and cover the objects with a glassy lustre. The heat must be sufficient to melt these gums, but low enough to avoid burning them. When the operation has been well performed, the pieces present a beautiful and uniform golden appearance, with no disfiguring red patches, which latter indicate an unequal thickness of varnish.

Varnishers have always at their disposition four varnishes of different shades,-red gold, orange-yellow gold, green gold, and colorless varnish for mixtures. This last is employed for diluting the first three and diminishing

the depth of their colors. Each of these various varnishes gives to copper the gold color peculiar to it, and, when mixed, intermediary shades. It often happens that the various parts of a large piece are different in composition and color, and the varnisher is obliged to impart the same shade of gold all over, by skilful combinations of varnishes. He thus succeeds in giving the same gold color to halfred copper, and to alloys of yellow and green brass.

But a small quantity of varnish is poured into the varnish pot at one time, in order to prevent it from thickening by evaporation, and, after the operation, the residue is poured back into the flask from which it was taken and kept well stoppered. The brushes and pencils must be often washed in alcohol, which may afterwards be used for diluting thick varnishes.

These varnishes are made by dissolving various resinous substances, like sandarach, benzoin, dragon's-blood, elemi, gamboge, etc., and tinctorial matters, such as saffron, annotto, alkanet, etc., in a mixture of alcohol with essence of lavender or of spikenard. All qualities of varnishes are to be found, but the more expensive are often the more economical.

To remove the varnish from an imperfectly varnished piece, or from an old one, it is immersed in alcohol or concentrated sulphuric acid, or, better still, in a boiling solution of caustic lye. The varnishing is then begun.

anew.