ENAMELING.
Enamel may be applied to metal objects and add a great deal to their
value and attractiveness if used sparingly. The enamels most used are
transparent and opaque; the transparent reflects the color of the metal
adding a great deal of life to the work, the opaque gives color on the
surface only.
The process, as described in this chapter, touches but the elementary
stages of the art that are within the possibilities of high school work
and possibly the upper grammar grades.
Enamel may be applied by any of the following methods:
First: By covering the entire surface of the object with enamel.
Second: By using a flat wire which is bent into sections the shape of
the design and soldered to the object; the wire forms partitions to
receive the enamel.
Third: By cutting away the design by the use of engraving tools, making
channels about 1/32 of an inch deep to receive the enamel.
Fourth: By using a chasing tool either from the front or from the back
of the work, forming raised or sunken partitions to receive the enamel.
The first and second methods are difficult ones, requiring a great deal
of experience in handling metal and enamel to obtain satisfactory
results.
The third and fourth methods are comparatively simple and are within the
possibilities of those for whom this book is intended.
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.
[Illustration: 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.
[Illustration: FIGURE 35.]
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. The soldering is protected by placing a paste
made of yellow ochre and water about the soldered joint both inside and
outside of the strip. The more of this clay we bank about the joint the
more protection there is. When the above has been done, the object must
be left in some warm place until the moisture from both the enamel and
the clay is thoroughly evaporated. It is then ready for firing. If the
blow-pipe or the Bunsen burner is used, take a tripod and place a piece
of heavy iron netting over the top and place the object on top of the
netting. The flame should always be applied to the under side. Watch the
enamel as the firing goes on and when it settles and glazes the heat
should be withdrawn. The object should be allowed to cool very slowly.
Hurrying at this point only increases chances for accidents. If, when
cool, it is found that the channels in places are not full of enamel,
the object is again cleaned in the nitric acid, more enamel applied, and
fired as at first. The cover is now ready to finish. The enamel may be
stoned down level with the top with an emery stone, or it may be left
just as it comes from the fire in the first place. If stoned down, it is
necessary to fire it again just enough to give it a glazed surface.
The directions as given apply to either transparent or opaque enamel;
but, in addition to the above, when transparent enamel is used, the
surface to be enameled must first receive a coating of flux to retain
the transparency. The flux is treated and applied just the same as the
enamel already described.
The upper half of Plate 26 shows boxes treated with enamel.