Mother of Pearl Inlay Technique, Part II


Epiphone Sheraton II with Mother of Pearl Custom Guitar InlaysII. Inlay Patterns, Layout, and Pearl Cutting

When last we met I spoke of tools and mate­ri­als (in Part I of this series), 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 rea­sons are sim­ple: abalone tends to be some­what more brit­tle than pearl and most abalone is almost twice as cost­ly as moth­er of pearl (or more). Moth­er of pearl and abalone blanks and lam­i­nates and oth­er inlay mate­ri­als are avail­able from luthi­er sup­ply com­pa­nies and from spe­cial­ty sup­pli­ers. I have my favorites among both types of mer­chants but I’ll leave it to you to devel­op your own. Many sup­pli­ers also sell machine cut inlays and some sell inlaid fin­ger­boards and peg­head over­lays but that’s not why you’re here.

I have seen pearl adver­tised in thick­ness­es that range from 0.02 to 0.06 inch­es. Inlays less than 0.04” are usu­al­ly pret­ty translu­cent and may not con­trast well with wood. Use 0.04″ blanks for flat sur­faces, and thick­er mate­r­i­al for curved sur­faces, such as arched gui­tar fin­ger­boards. Thick blanks are also less like­ly to break as they are cut. Thick blanks do increase the rate of blade break­age, so be sure to have an ample stock of medi­um blades avail­able. Moth­er of 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 although an ounce of thin­ner blanks will cut all of the fin­ger­board pieces it will not usu­al­ly cut the peg­head pieces (even though 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 best blanks from any giv­en batch and stash them away for some future ulti­mate inlay job. Look care­ful­ly at each blank and wet it to reveal unsus­pect­ed fig­ure and col­or. Check both sides. 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. 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 project fail­ure on the heels of a suc­cess­ful first inlay job. I don’t rec­om­mend alter­ing even these instru­ments, and please do not tam­per with a fine or col­lec­table instru­ment (don’t laugh—too many great instru­ments have been “cus­tomized” with mis­be­got­ten pearl inlays). Like many oth­er aspir­ing inlay arti­sans, I start­ed by inlay­ing a repro­duc­tion Gib­son ban­jo neck. This is one of the best ways to learn because most of the “pre­war” Gib­son Mas­ter­tone pat­terns are rel­a­tive­ly easy to cut, 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 (assum­ing you have a project that would use such a pat­tern). Select a pat­tern in keep­ing with the instrument–a 1920’s Gib­son tenor ban­jo pat­tern would look pret­ty strange on a gui­tar neck. The best time to inlay a new fin­ger­board and peg­head over­lay on a new neck is after both are glued in place and the neck and peg­head are pro­filed and bound and the bind­ing has been lev­eled with the play­ing sur­face of the fin­ger­board, but before the peg­head is reduced to final thick­ness and the neck is shaped. The squared unshaped neck back sur­face is much eas­i­er to con­trol and any dings that hap­pen dur­ing the inlay work will be removed when the neck is shaped. If a ban­jo neck is not part of your present or future world, you could also just inlay a box, a crib­bage board, or some­thing sim­i­lar. The impor­tant thing is to get to work.

If you are more adven­tur­ous and want to design your own pat­tern, by all means do so. Get ideas from extant inlay 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 vel­lum, 10 squares to the inch, which is avail­able from art and graph­ics suppliers—megabucks but worth it). You can work with­in a delin­eat­ed area the exact size of the sur­face to be inlayed, or you can draw much larg­er pat­terns to be reduced pho­to­graph­i­cal­ly or Xero­graph­i­cal­ly to actu­al size. I work up script pat­terns (like my brand name) by writ­ing with a medi­um-wide cal­lig­ra­phy pen until I have the pat­tern I like and that fits in the assigned space. 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 tech­ni­cal pen or “crowquill” pen and India ink. Oth­er types of pat­terns can be drawn 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. 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 each paper pat­tern piece to a piece of pearl with a very thin lay­er of Tite­bond or white glue, 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. These days many peo­ple design or scan inlay pat­terns on the com­put­er and print them on adhe­sive labels and I can’t think of a sin­gle dis­ad­van­tage to that approach except that you have to own a com­put­er and print­er. Oth­er­wise, as not­ed 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. Clamp your cut­ting jig to a table and set up the work light. Mount 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, which you can ascer­tain by run­ning a fin­ger­tip gen­tly along the blade in each direc­tion. The rough, snag­gy direc­tion is oppo­site the one where the teeth point. Use the ten­sion­ing mech­a­nism to tight­en the blade so that it yields very lit­tle when plucked like a string (or flex the saw frame to ten­sion the blade if you have that type of saw). When you mount the blade, be care­ful to avoid bend­ing or twist­ing the ends, and make cer­tain that the blade is as straight as pos­si­ble. Put on your res­pi­ra­tor or N95 and fire up the MP3 play­er. 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. If you’re not already the patient sort you’ll need to learn how to be. 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 open­ing or 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 or oth­er open­ing 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. When pos­si­ble cut from weak­er parts of the pat­tern into stronger sec­tions, but learn to cut from any point in any inlay. 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 now and again a par­tial­ly-cut inlay will break when the blade breaks. Like­wise, once in a while a blade piece will fly when it breaks, so you might con­sid­er includ­ing gog­gles in your per­son­al pro­tec­tive equip­ment arse­nal. 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 blanks and oth­er irre­place­able items.

If you need to file the inlay edge(s), hold the inlay on the cut­ting jig and care­ful­ly file down­ward, slow­ly. A small sand­ing wheel in a high speed drill can be use­ful for some smooth­ing, but try to cut smooth lines with the jew­el­er’s saw so that you don’t have to try to improve the inlay by fil­ing or sand­ing after the cut­ting is fin­ished. Also, do not attempt to inlay bro­ken pieces, glued or not. Throw them away, save them for prac­tice with engrav­ing, what­ev­er, but don’t include them in a fine inlay job. If you pro­ceed slow­ly, care­ful­ly, and thought­ful­ly 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 ear­ly inlays that are not as nice as lat­er efforts. 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 use sub­stan­dard inlays, for once their shapes are inscribed in wood, you’re com­mit­ted to them.

Fit­ting or “piec­ing” inlays togeth­er such as in a vine or more elab­o­rate pat­terns is pret­ty straight­for­ward but requires expe­ri­ence and mega-patience to do well. First cut the inlays care­ful­ly so that min­i­mal fur­ther work will be need­ed to achieve a gap-free fit. If fur­ther work is need­ed, use the small mill or nee­dle file. Hold the inlay on the wood­en jig or any small wood­en board so that the “fit­ting” region bare­ly pro­trudes and file care­ful­ly, hor­i­zon­tal­ly, ver­ti­cal­ly, and slow­ly. Start at one end or cor­ner of the design and work through it as uni­di­rec­tion­al­ly as pos­si­ble. Work on just one inlay in a fit­ted pair, not both—filing both will com­pound your errors (not to be con­fused with smoothing—you might have to do that to the join­ing sur­faces of both inlays before attempt­ing to file-fit them togeth­er). Try the fit fre­quent­ly until the inlays fit togeth­er with­out gaps, in the cor­rect ori­en­ta­tion so that one inlay “flows” smooth­ly into the next as designed. If you neglect to main­tain the flow between com­po­nent inlays, unfore­seen gaps or a cock­eyed pat­tern will like­ly result when the motif is inlayed. Assem­ble the com­plet­ed fit­ted motif on the table and study each joint care­ful­ly to detect gaps and places where the flow isn’t quite right, then cor­rect the prob­lem areas as care­ful­ly as you can to ensure that new prob­lems don’t emerge.

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 glued to a paper back­ing before it is cut. Bone for inlay should be at least .06″ thick, because thin­ner bone is translu­cent and does not con­trast well with wood. Sheet brass, nick­el sil­ver, and gold looka­likes are fair­ly easy to cut, although some­what hard­er on jew­el­er’s blades than is pearl. I have no expe­ri­ence with stone or “recon­sti­tut­ed” stone com­pos­ites but I expect that each has its own sur­mount­able prob­lems, just as pearl does. The use of ivory is right­ly con­tro­ver­sial and raw ivory is very right­ly almost impos­si­ble to obtain any more. Should you wish to inlay some old ivory, old piano key tops are the most com­mon source these days. These tend to be quite frag­ile and translu­cent and they do not make the most sat­is­fac­to­ry inlay mate­r­i­al. Ivory became obso­lete as a dec­o­ra­tive mate­r­i­al in about 1862 when cel­lu­loid was invent­ed and as a struc­tur­al mate­r­i­al it became obso­lete when bone first came along (a real­ly long time ago). In my opin­ion the only valid rea­son to use ivory is for repair of orig­i­nal ivory fit­tings or inlays on old instru­ments.

Con­tin­ue to Part III, Rout­ing and inlay­ing…


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