The parts of the design in heavy color may be treated in several
ways. A very satisfactory treatment is obtained by etching, then
coloring. Clean the metal thoroughly with pumice stone and water
or with alcohol before the design is applied. Cover all the metal
that is not to be lowered with a thick coating of asphaltum. Allow
this to dry, then put on a second coat. After this has dried,
thoroughly immerse the metal in a solution composed as follows: 3
parts water, 1 part sulphuric acid, 1 part nitric acid.
Allow the metal to remain in this solution until the exposed part
has been eaten about 1/32 in. deep, then remove it and clean off
the asphaltum, using turpentine. Do not put the hands in the
solution, but use a swab on a stick.
For coloring olive green, use 2 parts water to 1 part permuriate
of iron. Apply with a small brush.
The lines at A and B will need to be cut, using a small metal saw.
Pierce a hole with a small drill, Fig. 3, large enough to receive
the saw and cut along the lines as in Fig. 4. A piece of wood with
a V-shaped notch which is fastened firmly to the bench forms the
best place in which to do such sawing.
Pages:
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54