This picture is of the “arm pit” of a Ridgewing guitar frame, a rear view of where the flying buttress diverges from the center body, blends into the outline of the guitar around the waist, then and becomes the perimeter wrapped around the lower bout. The two holes are of thirteen molded into the underside of each frame, and will be press-fitted with M3 threaded brass inserts. This hole pattern provides a constellation of attachment point options for various body frame inserts, such as grills, solid wood pieces, or any other kind of construct one can imagine for connecting the strings and bridge to the rest of the instrument.

Zooming in, we can start to see what hand-finishing of homemade graphite-epoxy looks like up close. The little white spots on the lowerside are small air bubbles, arch enemies of the molder. Actually these are quite minor. Larger bubbles are removed through outgassing of the epoxy in a high vacuum chamber after it is mixed but before it is poured in the mold. Even these tiny bubbles can be gotten rid of when you go to a high-pressure process, where the curing epoxy gets squeezed with up to ten atmospheres of compressed air, and the wee little bubbles become wee, wee, wee little bubbles too small to see. The wet-layup process used here cures at atmospheric pressure, which is simple but lets bubbles survive. 

The tricks to making bubbles disappear start with adding a lot of very black fine carbon powder into the mixed liquid epoxy to make it opaque, which serves later to hide defects which are below the surface. For larger bubbles and voids which break the surface, good old Bondo is a wonder. A black wax filler (a/k/a black shoe polish) rubbed into the surface fills up the little guys. Then it is time to buff out.

This West System marine epoxy is much softer than the lacquer used on regular guitars, so it is pretty much impossible to go for a high gloss finish. Gloss would reveal too many little goobers anyway, so one learns to find love in settling for less, or at least different. Instead of the multiple graded wet-sandings used to build up that hard acrylic lacquer shine, the epoxy finish is a little light sanding over rough spots, the fine scratches you can see here, and then straight to the finish line with 0000-steel wool. As low-tech as it sounds, four-ought steel wool leaves an uncanny beautiful satin sheen surface on the epoxy, smooth and warm to look at as well as to touch. Over time, it starts to shine in places where it is in contact with hands like on the neck. And fixing dings is a cinch – deep ones fill with black super glue or black epoxy, then use a small file to level things out and blend the contours, then sand up the surface again starting at 220 grit, then 320 or 400. On regular lacquer you would normally take it up to 4000 or 8000 grit in five or six very careful and time-consuming steps to get to a high gloss, which occurs when the scratches on the surface become smaller than the wavelength of light. But through the magic 0000 steel wool, some rubba-dub-dub, and you are back in business.