RAISED FORMS.
The first exercise in raising should be a form quite simple in outline,
Plate 34 A. A drawing or blue print should be used showing the shape and
dimensions and this should be worked to as closely as possible. Next
select a piece of copper suitable in thickness for an object of this
size, in this case 20 gauge. The metal for raising must be circular in
shape and the diameter of the piece needed for this bowl determined in
the following way:
Take a piece of string, place it on the drawing or blue print, starting
in the center of the base, and follow the curve as indicated at A, on
Plate 34. This will give the radius needed for describing the circle,
which is 5-1/2". The circle is then cut out with the shears, after which
another circle is described on the metal for the base. All lines made on
the metal should be made quite lightly.
As a rule the copper comes from the rolling mill somewhat hardened so
the next thing to do is to soften it by a process called annealing.
Place upon the annealing tray, Figure 1, the circular piece of metal
already cut, and apply the flame from the blow-pipe upon it until it
becomes red hot. It is either allowed to cool off gradually or dipped in
cold water and then dried in the sawdust.
Select an anvil the shape of which conforms somewhat to the outline of
the bowl and also to the curve of the base. It is often necessary to use
several anvils to complete an object, but a little experience will help
to decide which should be used first. The No. 1 anvil on Plate 1 seems
to be about what is needed for this particular piece of work.
[Illustration: PLATE 34. RAISED FORMS]
[Illustration: FIGURE 23.]
[Illustration: FIGURE 24.]
The anvil is placed in the vise and the metal held in the left hand
against the anvil so that the end of the anvil comes directly under the
circle which represents the base, as shown at Figure 23. With a raising
hammer, No. 3 on Plate 2, begin hammering with light blows at first,
following the circle closely the first time around until the base is
well started. This operation is continued at each turn striking a
little above the previous blows until the top is reached when it will
take the shape as shown at Figure 24. Sometimes a horn or box-wood
mallet is used to start a piece of work. As the hammering hardens the
metal it is necessary to anneal it each time after going over the
surface. After this is done, we proceed as at first until the required
form is obtained as called for by the drawing.
Care must be taken not to stretch the metal any more than can be helped
as the more it is stretched the thinner it becomes.
The surface and outline of the bowl left by the raising hammer is quite
irregular and needs to be trued up by a process called planishing; for
this a No. 2 or 4 hammer, Plate 2, with a polished face and somewhat
broader than the raising hammer is used. By going over the surface with
this hammer all irregularities are removed leaving a refined curve and a
finished surface.
If the bottom gets a little out of shape during the operation of
raising, it can be easily brought back again by using a No. 2 stake,
Plate 1, and a No. 5 hammer, Plate 2.
During the raising process the top edge has also become very irregular
and must now be trimmed off level. Place the bowl on some level surface
(a surface plate will give the best results) and with the point in the
surface gauge describe a line about the top making it the desired
height, Figure 25. A small pair of shears is then used to trim off the
top to the line, after which a file is used to finish the edge, leaving
it perfectly smooth. A piece of fine emery cloth may be used at the
last.
[Illustration: PLATE 35.]
The principle of raising as here described applies to forms of all sorts
with few variations. Where a form is to be raised with the top edge
turned in as at B, Plate 34, an anvil similar to the outline must be
used. In raising a form like C, Plate 34, the sides are carried up as
shown by the dotted lines and then the form is reversed and the neck
part drawn in. A deep form is raised more quickly if, at the start, the
metal is placed on a crinkling block and the edge crinkled.
[Illustration: FIGURE 25.]
In all raised work after one becomes acquainted with the material, it
will be found that the metal can be forced in any direction, giving
thickness at the bottom, at the sides, or at the rim, as is necessary.
[Illustration: PLATE 36. PITCHERS]
After raising a form like C, Plate 34, it may be desired to increase the
diameter a little at o-o, where an anvil cannot be used; or, if the form
is satisfactory it may be necessary to raise certain parts of it to
carry out the decoration called for by the design. This is done by the
use of the snarling-iron, made as illustrated at Figure 26, which shows
the general outline only, as the ends vary in form according to the work
they are to do. One arm of the iron is held in the vise as at Figure 27.
The form is then placed over the end and held with the left hand while,
with a hammer in the right hand, the iron is struck quite near the end
in the vise which causes the other end to rebound. This serves the same
purpose as a direct blow from a hammer, except that it works much more
slowly.
[Illustration: FIGURE 26.]
[Illustration]
[Illustration: FIGURE 27.]
[Illustration]
[Illustration: PLATE 37.]
[Illustration: PLATE 38.]