The shell available in the past was for the most part small, thick, and crudely ground flat on one side. They were randomly placed in letter centers or backgrounds with damar and quick rubbing varnish, then the gaps filled in with various material, the most common being crushed pearl, gold glitter, or diamond dust, also wrinkled or embossed tin foil was widely used, more to fill gaps than for reflection. The shell’s greatest effect is from light reflecting off the face. Light passing or reflected through the shell gives a neutral or lightly opalescent look but does nothing to enhance its iridescence. The availability these days is limited to thick material (approx. 60 thousandths, compared to our 8 to 10 thousandths) for musical instrument inlay when and if you can find it. Hence was our incentive to produce our own supplies and progressively for other sign artists.
To form the shape desired, score the face with an x-acto knife with or without a straight edge, then snap it in half between thumbs and forefingers (with score upwards) to separate. Small pliers may be used for curves and to nibble off narrow edges, much the same as cutting glass or thin plastics. A carbide wheel glasscutter may also be used for curves or for where a knife blade wants to follow the grain of the shell. For tight seamed mosaic, clean up edge lightly with a small fine file. I prefer to entirely finish the work, saving only clear portions for the shell and the final protective coat.
To do a letter fill, with the work laying flat on the bench, mix up some damar and rubbing varnish (as for an embossed center) apply liberally to both sign and pearl face, randomly laying pieces (approx. ½” square on a 3” high letter) one at a time and partially covering letter outline with about 1/16” to 1/8” gaps between pieces. Lightly press with finger to force out any bubbles, then sprinkle seams with “fill” material. Let dry overnight or until pieces are set. Clear coat over the entire job as you normally would and after it sets up use back-up color to clean up any ragged letter outlines. If foil is desired, after pearl is set, re-varnish heavy over the back and press in foil to cover entire inlay. I have normally found foil back up only where the work was to be framed and the rear obscured. Two notes- be sure to let the clear over the pearl completely dry before cutting in with back-up, and prior to setting in shell, check each piece by rotating for optimum iridescence.
For vertical work, let the varnish on both faces flash off so as not to slide when affixed to the glass. Smaller areas without fill such as bullets are better suited for varnish affixing. In vertical work, I successfully use an industrial grade instant “cyanoacrylate” glue (an optically clear, no fogging formula which we carry in stock.) This adhesive allows you to fill large areas of center, 25 sq.in. or so per letter without sliding and and tightly fitting them together in a mosaic style without open seams. Runs with this material do not immediately lift surrounding japans and take roughly an hour to evaporate when left open to the air. I lightly wipe runs over the back-up, but not over areas to be inlayed. I set the abalone using a 6” length of dowelling with a lightly rubbed tip of double sided tape, dry fitting first with each piece, then applying adhesive to to pearl face only, shaking off excess and lightly placing pearl in place only as far as to force out bubbles then separate from dowel. Do not press too hard or air may be sucked back under shell, in which case force bubbles back out and flood glue at edge to draw back into air pockets. Do not attempt to remove piece if it has come in contact with gold, paint, or back-up. When finished back and clean up as before. If down the line, the job must be removed, a sharp razor blade poses no problem. Personal experience will dictate your favorite methods, but I recommend testing a few pieces on plain glass to be sure of inlay procedures.