There are many techniques in which contrasting metals are placed side
by side. Those that can properly be called inlay require a mechanical
attachment to secure a soft material into a harder one.
|10.12 Gunlock, Steel with silver inlay, some looses. Middle 18th
century. (State museum, Schweirn)
Proper inlay requires materials of contrasting hardness to hold well,
and contrasting color to look good. A combination that does well on both
counts is the use of pure silver or gold into blackened steel. Another
popular combination has fine silver pressed into copper or brass. Examples
can be found in museums, particularly in weapons and decorative objects
Creating the Cavities
The principal behind metal inlays is that wire or pieces of sheet are
forced into cavities or hollowed out areas. These are cut so their walls
slope inward, or are undercut. This insures that a piece of metal will
get stuck there once it is forcibly rammed in. It is a simple process
and judging from the fact that we can find inlays that are many hundreds
of years old, an effective one. While the pressing in requires sensitive
hammering, the most important part of inlay work lies in cutting the cavity
in the first place. There are several methods available to a metalsmith.
The process is worked as described in Chapter 10, section 7, with nitric
acid being the preferred mordant in this case. As the acid works its way
deeper into the metal it has a natural tendency to also work outward,
creating exactly the undercut that is needed. Unfortunately this is not
the natural tendency of ferric chloride, which has the usually agreeable
tendency to leave a vertical wall.
Burring or milling
In a miniature milling operation, a bur can be used in the flexible shaft
machine to remove metal. Once the cavity has been excavated with a ball,
barrel, or similar bur, the walls are given the necessary undercut with
an inverted cone bur or with a narrow graver.
Each piece will present unique approaches, so it is best to let your
instincts guide you. The point is to create a cavity with sharp edges,
a uniform depth, and undercut walls. A tube or other curved surface can
sometimes be decorated with a sawblade, a chisel or a bur, or a combination
An ideal approach for delicate linear designs is to make a pair of cuts
with a narrow onglette graver. This tool is driven along a drawn line
at a steep angle, as shown in figure 10.18b. The same tool is then passed
along the same line at the opposite slant, creating a cavity with a swallowtailed
|10.18 Inlay with engraved recesses
a - raising a bead, side view
b - First cut
c - Second cut to inset wire
e- Inserted wire hammered into place
In cases where the desired inlay is larger than a wire, sheet material
is used. In these cases, a square graver is used to excavate the area,
then the onglette is used around the edges to create the undercut. This
is shown in figure 10.10c.
Using chisels to cut away sections of metal sheet is an effective technique
that has the advantage of being relatively easy to learn. The metal is
secured on pitch as for repoussé, or in some similar way clamped
onto a sturdy work surface. Chisels of several sizes will probably be
needed, each taking the shape shown in figure 10.19b. The tool is held
between the thumb and the two first fingers and struck lightly with a
small hammer. Particularly when first learning, avoid the mistake of gouging
out too much at a time. Think of shaving off layers of metal until the
proper depth is reached. The cavity should have smooth walls and a flat
bottom and attain a uniform depth throughout.
|10.19 Inlay with chiseled groove
a - chisel cut, side view
b - chisel cut
c - chiseled groove
d- tapping down the ridge
e- hammered inlay completed
It is usually best to first make the cavity walls straight, focusing
on the correct shape for the cut. When this is achieved, use another chisel
and go around the inside of the form to undercut the walls slightly. Where
small wires are to be inlaid, an alternate method is to use a chisel to
pull up a bur along the edge as shown in figure 10.20d.
|10.20 Inlay with punched grooves
a - punch side view
b - incised groove
c - flat punches side view
d- enlarging the channel
e - hitting down the edge
f - finished inlaid wire
g - rounding off the inlaid wire for relief inlay
This method is similar to chiseling except that no metal is removed. Because
of this it is not recommended for large inlays, though it can be very
efficient for small wires. Select a sharp liner that will cast up a bur
on both sides of its mark. Use magnification to check the results of the
too (figure 10.20b).
Follow the first cut with another punch, this one a flat-ended punch
that will widen the groove to accept the inlay (figure 10.20d). Only a
small amount of metal is needed to secure the wire but it must stand up
above the surface as shown. It is important to select tools of the proper
size and strike each blow cleanly so the tiny bur is not accidentally
Fixing the Inlay in Place
Wire inlay into undercuts
Use an annealed wire that is a proper fit for the groove. A wire that
is too small will not be securely held while an oversize wire risks distorting
the inlay (as well as requiring tedious extra finishing). Start at one
end of the groove, tapping the wire lightly into place for a short distance,
than proceed to the next area. The idea, seen in figure 10.18d and e,
is to press the wire outward into the swallowtail or undercut area, locking
it into place. The action has the added advantage of work hardening the
Once the wire is firmly pressed into place, use a smooth-faced planishing
punch to even the surface and refine the inlay. Make a series of light
passes over the wire and surrounding area, feathering the surface until
it is flush.
In the case of a groove cut with a chisel or punch, in which the edge
of the cavity has been thrown up in a delicate bur, the process is a little
different. The wire is set into position and a slightly roughened matting
punch is used to gather the material immediately adjacent to the groove
and press it onto the wire, figure 10.20e. A variation on this is to create
a roughened punch with a slight arc in its center, shown at figure 10.20g.
This tool spans the wire and presses down on the inlay to lock it in place.
Once it is secure, planishing hammers, files and sandpapers are used to
make the surface flush.
A cavity is made as described above, using either chisels, gravers or
through acid etching. The walls of the cavity are undercut, causing them
to slope inward. A piece of sheet metal a little thicker than the depth
of the cavity is cut out and filed so its edges are beveled to resemble
the slope of the walls. The piece is domed slightly, which will allow
it to drop into the cavity. Measurement and close tolerances are clearly
Once it is in place the sheet is flattened with a mallet or punches,
which causes it to press against the undercut walls, locking it into place.
The surface is planished then refined with sandpaper.
While most inlays are flush, it is also possible to create an inlay that
stands above the surface of the base. In the case of sheet inlays, the
piece might be formed through repoussé or casting. The inlay process
is the same as described above but of course the inlay panel must not
be planished. Instead it is pressed flat with carefully located punches
that will not damage the shape on the panel.
In the case of wires, the round wire mentioned above is replaced with
a flattened wire, the smaller dimension of which fits snugly into a groove
that has had a bur thrown up along both sides. A matting punch is used
along the side of the wire to press the bur against it, alternating from
one side to the other. To cinch the inlay use a flat-faced punch that
has a groove the width and height of the projecting element cut into it.
This punch, called a veining tool, travels along the metal, tapping the
base piece against the sides of the wire and trapping it into position.