In the case of the jar cover the cells were made by the chasing method, Fig. 143. The cover was filled with chaser's pitch, then stuck on to the pitch block,15 and the design was outlined with the "tracers" and the cells were made by beating the metal down with the "planishers." This style of chasing is known as "recess"
Fig. 143. Jar cover ready for enamel; chased cells.
Fig. 144 Jar cover after second firing.
Fig. 146. Square box cover with enameled handle.
Fig. 147. Chased silver hat-pin background of blue enamel.
chasing, and makes an easy and effective method of decoration in itself. The same cover is shown after two coats of enamel have been melted on, Fig. 144. It is now ready for grinding level with the carborundum stone, and the final firing to obtain a smooth, shiny surface. The square box cover, Fig. 146, is another application of the chased cells. The chased silver hat-pin, Fig. 147, is a further modification of chasing and enameling. When champleve cells are made and a design chased or carved in the bottom of the cell, the name basse-taille relief, or repousse, is given to the work.
Fig. 148. Mortar and pestle, pieces of enamel, spatula, and carborundum stone.
'"See Fig. 134, p. 163.
A transparent enamel is always used with this type, the design at the bottom being seen thru the enamel.
Etching, sawing, and chasing are the easiest methods of making the cells for the enamel. These having been described, we will now" take up a description of enamel and the methods of applying and firing it. As stated before, enamel is a glass that is colored with metallic oxides. Opaque white is colored with oxide of tin, cobalt blue with oxide of cobalt, yellow with oxide of uranium, green and turquoise with oxide of iron, violet and purple with oxide of manganese, and so on thru many various shades and colors. All colors may be obtained in opaque or transparent enamel. The enamel is bought by the ounce, and comes in flat cakes about 5" in diameter and 1/4" thick.
The enamel is broken into small pieces with a hammer and ground to powder in a wedgewood mortar with the pestle. A 3" mortar is plenty large enough for the beginner. Fig. 148 shows the materials referred to. It is best to have a little water in the mortar to stop the small pieces of enamel from flying out. Do not pound the enamel, but place the mortar on a chair and make use of the weight of the body to grind the enamel.
After the enamel is ground about as fine as the finest salt, wash it by filling the mortar with water, allowing the enamel to settle; then pour off the water, which will be somewhat milky in color; repeat this two or three times, until the water is clear. Then fill the cells with the wet enamel, using the spatula as a spoon. The spatula is a piece of 1/8" square steel hammered to a spoon shape on one end and to a point on the other. When the cells are full, tap the edge of the metal with the spatula. This will make any air bubbles come to the surface and will make the enamel settle down perfectly smooth. Care must be taken to fill the cells carefully and not to leave any enamel on the metal surface. Next apply the edge of a piece of soft blotting paper to the edge of the enamel; this will draw off the water. The enamel is now ready for firing. Small pieces may be fired over a Bunsen bruner or any blue gas flame; the larger pieces, requiring more heat, may be fired over the hotter blowpipe flame. But in either case it is absolutely necessary that the flame should not come in contact with the enamel, as the flame will reduce the metallic oxide with which the enamel is colored, and spoil the color of the enamel. A twisted flattened bunch of fine iron wire is a good support for the piece while it is being fired. Heat the piece slowly until the moisture in the enamel is evaporated, then hold the piece steadily in the flame until the enamel melts and glazes. Allow it to cool slowly, as any sudden cooling is liable to crack the enamel. The enamel will have shrunk considerably in the firing, and it will be necessary to fill the cells a second and perhaps a third time, if it is desired to have them full and level. If the enamel is to be flush and smooth with the surface of the metal, it may be ground level with the carborundum stone wet with water, or with a smooth sharp file. The piece is then fired again to get the finish glaze. Sometimes the cells are first filled with a colorless transparent enamel, called "fondant" or "flux"; and the colored enamel applied as a second filling; this makes the color lighter and more transparent.
Fig. 149. Inside construction of homemade enameling- muffle.
Fig. 150. Inexpensive bomemade enameling' muffle.
The pieces of enamel work that for any reason cannot be fired over the open flame of the Bunsen burner or blowpipe may be fired in a muffle. A muffle is a furnace in which the flames pass around a clay dome in such a way that the dome and the work get red-hot, but the flame does not touch the work. Muffles that are placed on sale are expensive, the cheapest costing about $17.00, and they are also expensive to operate, usually requiring about one hour to'melt the enamel. However, a perfectly satisfactory muffle can be easily made to use in connection with the blowpipe and foot bellows. The muffle shown, Fig. 150, is made from a two-gallon oil-can, some broken brick and fire clay, and a clay dome that costs seventy-five cents, making a total cost of about $2.00. This home-made muffle costs less to operate than the ones sold in the market, as it will',get hot and melt the enamel in about fifteen minutes. Figs. 149. and 150 show the manner in which the muffle is made. If at any time it is desired to remove small pieces or specks of enamel, repeated applications of hydrofluoric acid will remove them.
It is always advisable to test the enamel before using it on any valuable piece of work, as enamels are sometimes found the fusing point of which is higher than that of the metal it is to be melted on. I have had more uniform success with the enamels of the Chas. M. Robbins Co., Attleboro, Mass., altho Devoe and Reynolds, Drakenfeld & Co., and the John Dixon Co., all of New York City, sell good enamels of various grades. Some enamelers mix a very small amount of borax or a little oxide of lead with enamel that does not melt readily. This is a convenient thing to know for use in exceptional cases, but enamels treated in this way are never so good as when the proper materials are used. The best results are secured by buying good enamel and then testing before using.