In the third method the design is first transferred to the object by the use of carbon paper and then made more permanent with a scratcher. The design is cut out with the engraving tools, [Figures 6], [34] and [35], about 1/32 of an inch deep. All edges should be kept as smooth as possible and the channels should be uniform in depth. For convenience in holding, if the work is small, it may be fastened to a little pitch or wax spread on a block, or it may be placed on the pitch block as described under embossing on page [64]. The handle of the tool is held in the palm of the hand, and the thumb, placed within an inch of the point, serves as a guide while cutting,[Figures 34] and [35]. By wriggling the tool a little from one side to the other, greater progress is possible.
Figure 34.
In the fourth method the design is transferred to either side of the object. After placing it on a pitch block, depressions may be made from the face or lines raised from the under side.
After the partitions have been formed, the object must be thoroughly cleaned and brightened by dipping in a bath of nitric acid. After dipping, which should be done quickly on account of the rapid action of the acid on the metal, it should be rinsed thoroughly in clean water. This process removes all dirt and leaves the metal bright. After this cleaning, the fingers should not touch any part of the object that is to receive the enamel.
To prepare the enamel for application it must be ground. First break it into small pieces with a hammer. To keep it from flying about, it is well to roll it up in a piece of heavy wrapping paper. It is then placed in a porcelain mortar and, with a little water and a pestle, it is ground about as fine as fine sand. The water is poured off and the enamel rinsed several times in clean water until the milky substance disappears. Unsatisfactory results often come from lack of care in washing the enamel. After washing it is removed from the mortar to a small saucer by the use of a palette knife. While still wet, which allows its being spread more easily, the enamel is applied to the object with a soft hair brush.
All of the enameling suggested in this book may be done with an ordinary blow-pipe or a Bunsen burner, but more satisfactory results are obtained with a kiln.
To apply the process to a definite piece of work, the steps necessary in enameling the Stamp Box cover on [Plate 24], No. 3, will be taken up. It will be assumed that the box is made, ready for the application of the design as shown on the plate. The design is first transferred to the cover and then cut away. It is cleaned with kerosene and dipped in nitric acid as before explained. After being thoroughly washed, it is ready for the enamel. In applying the enamel care must be taken not to get particles outside of the channels. After the moisture has evaporated and the enamel has been fired it settles considerably so that this must be allowed for by rounding it above the surface. After the enamel has been applied, the strip that is soldered to the under side of the cover must be protected from the heat before firing, as the temperature required for fusing the enamel is several times greater than that required for soldering.