From ez01078–(at)–ocky.ucdavis.edu Wed Mar 20 00:08:44 CST 1996
Article: 9611 of rec.music.makers.builders
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From: ez01078–(at)–ocky.ucdavis.edu (Sean Barry)
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Subject: Pearl Inlay–Spring rerun, part II
Date: 20 Mar 1996 00:17:03 GMT
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Part II of same:

Pearl Inlay
Sean J. Barry
Davis, California

This is the second of the three-part series on instrument inlay. I’m
grateful for all of the positive feedback on Part I, and again I solicit
and welcome your comments. Disclaimers and copyright rules are still in
place.

II. Inlay patterns, layout, and pearl cutting

When last we met we spoke of tools and materials, and I left you staring
at an array of scribes, jeweler’s saws, thin blades, and noisy high speed
drills. Now, you must choose an instrument or other object to be inlaid,
purchase some inlay material, and either purchase or design a pattern to
cut. For your first effort, I suggest that you stay with mother of pearl
>from the pearl oyster, and save abalone for a later endeavor. The reason
is simply that abalone tends to be somewhat more brittle, and full of
fragile natural laminations (the black lines that help to make it so
attractive). If you insist on abalone for your first inlay job, use red
rather than green abalone because red is less fragile (and less
interesting) and generally comes in larger, more easily handled slabs–the
shells are larger. I have seen pearl advertised in thicknesses that range
>from 0.02 to 0.06 inches. Use material that is 0.02–0.04″ for flat
surfaces, and thicker material for curved surfaces, such as arched guitar
fingerboards. Thick slabs are also less likely to break as they are cut.
Thick slabs do cause a higher rate of blade breakage, so be sure to have
an ample stock of medium blades available. Pearl is sold by the piece or
by unit weight, typically by the ounce. Many suppliers claim that one
ounce is sufficient to cut a Gibson-style banjo neck, but I have found
that it will cut all of the fingerboard pieces but not usually the peghead
pieces (also, there are more thin than thick slabs to the ounce).
Further, many peghead patterns require oversize blanks (e.g. Gibson Flying
Eagle and Bella Voce), so if you have such special requirements be sure to
discuss them with the supplier. Most suppliers do not “grade” mother of
pearl (except to separate the “gold” pieces, which have a specialized
market), because highly figured pieces are scarce enough so that the cost
of sorting by hand would multiply the final cost of the pearl manyfold.
The end-user should pick out the especially attractive slabs from any
given batch and stash them away for the ultimate inlay job. In any case,
use as plain and routine a selection of pearl as possible for your first
cutting efforts.

The inlay design is dictated by the nature of your project, and for this,
you must choose carefully. Please do not commit a fine instrument to your
first inlay project, but don’t use a clunker either. I think that the
best instrumental candidates for practice material are instruments you
have built yourself or instrument necks you have built or purchased. You
might consider a medium- priced commercial instrument, one that is
unlikely ever to be collectable, but you will have to strip and refinish
the peghead, de-fret and refret the fingerboard, etc, none of which is
simple and all of which increases the likelihood of failure. I really
can’t recommend altering even these instruments. Whatever you decide,
please do not tamper with a collectable instrument–the value of your
1960’s D-28 for example, will decline substantially if you alter its
factory appointments, even if you do a first-rate job. Do it to a 1930’s
D-28 or a Loar and instrument connoisseurs will report you to the vintage
police. Like many others, I started by inlaying a reproduction Gibson
banjo neck, and this is one of the best ways to learn. Most of the 1920’s
and 1930’s Mastertone patterns are relatively easily cut (especially the
“Hearts and Flowers” pattern), and there are enough pieces in most of the
patterns to give you lots of practice in layout, cutting, and inlaying.
Banjos are generally very amenable to such decoration–in my opinion too
much pearl on a guitar or mandolin is too much pearl, but banjos rarely
have this problem. The various Gibson, Vega, Paramount, and other inlay
patterns are available from suppliers, and for your first effort you
should probably stick to one of those. Try to select a pattern in keeping
with the instrument–a 1920’s Gibson pattern looks pretty outlandish on a
Vega long-neck. Still, the important thing is to get to work, so as long
as you don’t irrevocably festoon a venerable collector’s piece with new
inlay you should be fine. You could also just do a box, a cribbage board,
or something similar.

If you are more adventurous and want to design your own pattern, by all
means do so. Get ideas from extant patterns, Grecian urns and columns,
$100 bills, TV test patterns, classic museum architecture, kitchen
fixtures, chandelier displays, or deep within yourself, and draw them on a
piece of translucent graph paper (I use Clearprint 100% rag, 10 squares to
the inch, which is available from art suppliers–megabucks but worth it).
I do script patterns (like my brand name) by writing with a medium-wide
calligraphy pen until I have the pattern I like (and that fits within the
space assigned–hence the translucent paper). Then I overlay a second
sheet of translucent paper on the design and trace carefully around the
edge of the script with a size-0 Kohinoor Rapidograph technical pen and
India Ink (I use Pelikan)–any technical pen or even a “crowquill” with a
fairly fine point and the right ink will work. Other patterns can be done
in pencil, and then traced with the technical pen. If you design your
first pattern, you will undoubtedly discover later as you are attempting
to cut the pearl that not all designs can be cut. Try to remember as you
design to keep straight lines straight, and curves as segments of a
circle, rather than as ovals. Remember that you will not appreciate your
design fully until it is embedded in the wood, after it is much too late
to change it, so try to keep it simple and elegant, especially the first
time out.

Lay out the pearl slabs on a table and examine each one to determine the
best side, and remove the figured pieces and put them in the safe deposit
box. Take your purchased or drawn pattern, make sure you have lots of
accurate photocopies, and with scissors cut out the individual designs. I
number each piece of the pattern so that all can be accounted for when the
layout is complete. Glue (with Titebond or white glue) each paper pattern
piece to a piece of pearl, and let the glue dry completely. Be sure to
glue edges and corners adequately, because these are likely to lift during
the subsequent cutting if not glued well. I have tried rubber cement and
contact glue and both have failed to hold the design in place along thin
areas and at corners. At least one of my correspondents designs patterns
on the computer and prints them on laser printer adhesive labels, an
approach definitely worth trying. Otherwise, use a very thin coat of
Titebond or white glue (thin to avoid gumming up the saw blade), and after
the glue has dried, it is time to cut the inlays (the use of Titebond or
white glue is still optional–if you like some other glue, try it). Clamp
your cutting jig to a table and set up the worklight. Install a blade in
the jeweler’s saw, and make certain that the teeth will cut on the
downward stroke–the teeth should point toward the saw handle. Use the
tensioning screw to tighten the blade so that it yields very little when
plucked like a string. When you install the blade, be especially careful
to avoid bending or twisting the ends, and make certain that the blade is
as straight as possible. Put on your dust mask and goggles and fire up
the CD player or the radio. There are peaceful but meticulous times
ahead.

To cut inlay well requires only that you be able to follow a line with the
jeweler’s saw. This was easy to write, but if you are like most it will
take many inlay-feet of cutting before you achieve the consistently
smooth, graceful line that characterizes expert work. Patience is not a
virtue when cutting inlay, patience IS cutting inlay. Many artisans like
to cut along the outside edge of the line, which they endeavor to keep to
the left of the blade as it lays on the jig. The left hand steadies,
moves, advances, indexes, and turns the pearl slab over the hole in the
jig and the right hand holds the saw handle beneath the jig, and saws up
and down (remember, set the teeth so _down_ is the cutting stroke) and
cuts the pattern. The saw should advance, turn or otherwise move very
little (except up and down)–that’s why the hole in the jig can be so
small. Examine the pattern thoughtfully before you start to cut. Look
for inherently weak areas, and plan the best route for the initial cut.
Cut into the slab near the end of a point or corner–if you are cutting
out a star, try to intersect the pattern at the apex of a point rather
than somewhere along a side. When you hit a tight corner, back up the
blade, cut a bit into the outside to widen the kerf, repeat if necessary,
and use the widened kerf to turn the blade around the corner. Try to cut
>from weaker parts of the pattern into stronger sections, but frequently
this will be impossible. Endeavor to cut long straight lines and curves
without stopping, because a small bump or ridge often results where the
cut is interrupted. Try to use the entire blade for each cutting stroke,
except when you are approaching a stopping point, but even here keep you
sawing movements as smooth as possible. To cut out “blind” interior
sections, drill a hole into the blind pocket with a pointed bit in the
Dremel high-speed drill, and then thread the saw blade through the hole
and install it into the saw–this is tricky and a threaded blade is
difficult to tighten, but you will improve with experience. Cut the blind
sections first, and for that matter, if you have delicate sections that
are not blind, try to cut them first as well. As your skill improves,
your pace will quicken, but be careful not to cut too fast because the
blade will heat up and break. The other principal reason blades break is
that they bind in tight corners or from being forced to turn too tightly
to follow a tight curve. Blades also break when the metal fatigues from
use, or simply because they get dull. Again, be sure you have lots of
blades on hand. Blades usually just break without causing problems, but I
have had partially-cut inlays break when the blade broke. Once in a while
a blade piece will fly when it breaks, hence the recommendation to wear
goggles. Of course, you have been wearing a dust mask on your face (not
on the top of your head) during the entire cutting process. The blade can
also loosen somewhat during the cutting, which actually makes it easier to
cut but it wanders aimlessly. Be alert for this and tighten as necessary.
If this is a chronic problem, clean the blade attachment points or buy a
better jeweler’s saw frame. When the inlay is completely cut, carefully
examine it for problems and then put it in the safe deposit box along with
your figured pearl and family heirlooms.

As I said last time, do not rely on a file to smooth rough edges on your
inlays. The pearl is quite hard and it is difficult to hold small,
delicate inlays tightly enough to file without breaking. A small sanding
wheel in a Dremel can be useful for some smoothing, but in general try to
cut smooth lines with the jeweler’s saw so that you don’t have to try to
improve the inlay after the cutting is finished. Also, do not attempt to
inlay broken pieces, glued or not. Throw them away, save them for
practice, whatever, but don’t try to include them in a fine inlay job. If
you proceed slowly and carefully, your skill will improve dramatically
between the time you start and finish your first elaborate pattern, so
much so that you will probably want to recut some pieces that are not on
quality par with others. Rest assured that this skill will always
improve, no matter how much experience you have, and you will become more
critical of your own work as experience accumulates.

When you have cut all of the inlays, scrutinize them carefully– compare
and match paired patterns (such as opposite petals in the hearts and
flowers pattern) so that the final product reflects care and attention to
detail. Reject any inlays that are really clunky, but for a first attempt
don’t be too hard on yourself. However, the really meticulous (and
irreversible) work is soon to begin. Don’t commit substandard inlays to
it, for once your patterns are inscribed in wood, it is difficult to
change your plans.

Afterword: The above applies as well to other materials commonly used for
inlay. These differ physically from pearl quite substantially, but none
is especially difficult to cut. Wood veneer should preglued to a paper
backing before it is cut. Bone for inlay should be at least .06″ thick,
which is somewhat thicker than most pearl slabs, because thinner bone is
generally too translucent to make good, contrasting inlays. Sheet brass
is fairly easy to cut, although somewhat harder on jeweler’s blades than
is pearl. The use of ivory is rightly controversial (although I’m not
convinced that the lives of the oyster or the ebony tree are any less
valuable than that of the elephant), but should you wish to inlay some old
ivory, it cuts quite similarly to bone but is slightly less translucent.
Old piano key tops are a common source of inlay ivory, but these tend to
be quite fragile and are very translucent. Best to avoid ivory, but it is
a lovely material.

Next: Routing and inlaying