In this course we have thus far used four decorative processes outside of coloring, namely, etching, saw-piercing, planishing with the neck hammer, fluting and modeling. The electric light dome shown in Fig. 77 is a development of the lantern problem, and introduces a new process called "outline chasing," a process which is entirely suitable for public school work. Fig. 74 shows a piece of 20-gage copper tacked to a piece of one-inch board, with the design traced on one half and "chased" on the other half. This chasing, which is only the simplest kind of metal chasing, is done with two small chisel shaped tools that are called straight and curved tracers, and the ball-pein hammer.
Fig. 75. Method of "chasing."
The tracers can easily be made from a piece of 3/16' square steel rod, and should be about 4 1/4" long; one end should be filed to an edge like a small chisel, except not so sharp, with the edge dull and slightly rounding, so as to avoid cutting thru the metal. The edge of the curved tracer is filed so that the curve is about the same as a small section of a 3/4" circle. The tools and the correct position of holding and using them are shown in Fig. 75. It is rather difficult to follow the lines at first, so it is advisable to practice a little on a scrap piece of copper tacked to the board. Do not make a very heavy line the first time, but go over it a second and third time straightening and correcting it.
Fig. 76. Side of "dome" chased, and background cut out ready to berd in shape.
Fig. 76 shows the side of the dome chased, and the background cut out with a chisel, made and used in the same way as the chasing tools, except that it has a cutting edge which is kept sharp to cut thru the metal. After the chasing is done, and the background cut out, the metal is removed from the board, cut and bent to shape, and riveted together into the finished dome which is shown in Fig. 77. The ceiling plate was raised into shape and planished, in a manner similar to that described for the lantern-top in Chapter XIII (Beating Down, Fluting, Modeling).
Another adaption of this new process is shown in the sterling silver plate, Fig. 78. The same chasing tools were used as in the chasing of the dome, the steps in the process being: First, tack the flat piece of metal to the board by driving tacks thru the metal as near the edge as possible; Second, trace on the design; Third, chase the design; Fourth, remove from the board and trim the edge of the tack holes; Fifth, lap the edge; Sixth, beat down the depression; Seventh, planish and finish. See also Fig. 79.
Fig. 77. Electric light dome.
Fig. 78. Chased silver plate.