Pearl Inlay - Part II
Inlay Patterns, Layout, and Pearl Cutting
Sean J. Barry, Davis, California
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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 many fold. 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 work light. 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 be pre-glued 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.
Part III - Routing and Inlaying
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