Finishing and the Little Bits

With the neck and body in one guitar-like object at last, it comes time to start finishing up - which means constructing and detailing the little bits (truss rod covers, fingerguard/pickup assemblies, tailpieces, bridges) and wood finishing.

Regarding the finishing: I don't have a spray booth, but I decided to do a traditional full-gloss lacquer finish for these guitars. I used Belhen's Stringed Instrument Lacquer in aerosol cans, which worked better than I thought it might, and sprayed with what spray equipment I have at hand for final coats. Here is the full schedule of finishing, which will partly explain why I haven't posted lately:

• Wood filler on mahogany and cherry, and sand to 400#
• 2 coats lacquer and sand to 400#
• 3 coats lacquer and sand to 400#
• 3 coats lacquer and sand to 400#
• 3 coats lacquer and sand to 400#
• "dotting" imperfections, sand dots to 400#
• 3 coats lacquer
• wait 2 weeks
• wet sand to 600#
• polish by hand with medium and fine colortone abrasive
• final polish with colortone swirl remover

I taped off the maple bindings for wood filler.

Smearing on and smearing in the Timbermate water-based wood filler. 

Sanding off the wood filler. This stuff dried hard as a rock, and it took three days to sand it off. I had to be careful: too aggressive, and I could sand deeper than I wanted, less aggressive, nothing much happened. It's a good product, but next time I would squeegee it in, leaving a lot less on the surface.

First coat of varnish. The first couple of coats soaked right in. I sanded, then more - soaked in again. It wasn't until about 8 coats that I started to see anything "building" as a finish. Partly, I think, it was the aerosol cans, which don't deliver quite as much product per coat as regular spraying. I think the cans need a thinner product inside to spray properly, so they can still work when the pressure is so low towards the end of each can.

My son Brendan soldering the volume and tone controls to the Benedetto humbucker pickups mounted to the fingerguards, in the Psychoacoustics lab at Skidmore college, from which he graduated (with honors, ahem) a week or so after this photo was taken. Behind him is his beloved 3D printer. For the pickguards, I laminated curly cherry veneer onto solid cherry - same veneer as the flip side of the headstocks.

Fitting the ebony bridges to the curve of the tops. This was remarkably easy - just a lot of small stroked against 80 grit paper. I decided to do this midway in the finishing, so that any harm to the tops could be "rubbed out" - but no problems arose.

Pickguard/finger rest and ebony tailpieces. Because these are really acoustic guitars, what little electronic components there are stay separate from the body and unobtrusive. The Benedetto humbucker pickup is mounted to the floating fingerrest, and the volume and tone controls are mounted unobtrusively beneath it - just a liver of each dial shows.  Brendan wired a plug to the electronics which mates with the endpin jack, for easier disassembly and repair. I took a shortcut ith the ebony tailpieces, buying predrilled benedetto blanks, since my drill press is still shot from shaping the tops and backs. As it turns out, the predrilled, rough ebony blanks cost me less than buying a decent piece of ebony would have, so I figure I'm ahead of the game. I shaped the tailpiece blanks, and finishes the tops in wax alone, to match the fingerboards.

"Dotting." On the adv ice of Harry Becker, local luthier, I took a few days to "dot" all the minor cavities and imperfections in the finish with tiny dabs of lacquer, applied with a tiny pointy brush. I sanded these down flush before the final coats of lacquer.

Truss rod covers. I laminated a thin piece of burl (same backyard cherry burl as the headstock on the right in this photo) to a thin piece of maple for contrast, then inlaid a small MOP piece and shaped them.

Final coats of lacquer applied - waiting 2 weeks for it to evaporate to the extent that when I polish it it will stay polished, rather than shrink more (which would produce grain lines).

Wet sanding with 600# paper. A long, slow process, to get the surface dead flat for polishing. You can see the lacquered but not sanded surface at bottom right, the sanded but not shiny surface upper left.

Polishing. This was incredibly satisfying. From the dead flat surface arose a gloss finish. I used Colortone medium and fine abrasives, hand rubbed with white felt pads, followed by Colortone swirl remover and cotton cloth.

Final polishing - bringing up the gloss.

A finished back.

Finished cutaway on Brendan's guitar

Bottoms. Brendan's guitar (left) has gold hardware, mine is silver.

F-hole detail. Subtle, but I'm pleased.

Finished headstocks.

Finished backs.

Ready for Harry Becker to do setup. In a few weeks Brendan and I will each have a ne guitar!