Question (WOODWEB Member) :
I have a millwork shop but normally don't do any finishing so I am somewhat inexperienced. I have built a few guitar bodies out of African mahogany and can't figure out why the grain keeps sinking. I filled the raw body with Daly's wood filler (oil based) and allowed several days of drying.
After two coats of sanding sealer and several days of dry time before sanding with 320 grit there are no low spots visible and it looked glass smooth. I then shot it with gloss nitro lacquer, about four or five coats and the finish was super smooth, with the intent of letting that cure for a couple weeks before a final sand and another couple finish coats. After about a week the grain in the mahogany has become so pronounced I am not sure I can sand them out without removing the top coat! I used an HVLP gravity air setup and Lemar lacquers. Any thoughts on why?
Forum Responses
(Finishing Forum)
From contributor S:
If you insist on using nitro may I suggest this system: base color; washcoat - sealer cut up to 100%; this seals the bottom and inside edges of the pore; pore filler with adequate dry time; pore filler again with adequate dry time; sealer; full scuff; top coat(s). With a higher solids post catalyzed coating system you may not need a synthetic pore filler, unless you desire a contrast between the base color and the pore coloring.
Also, when removing the pore filler allow it to flash a wee bit prior to removal; and remove up to 90% by working in a circular motion as this assists in packing the filler into the pore. Finish the wiping with the grain. Next day if there are any traces of filler left you can safely remove with a rag slightly damp with naptha.
As to your piece in progress, you could sand it back to wood while leaving the pores with finish and filler (there is a long and varied history of this type of pore filling for leveling purposes going back more than a bit up to at least mid to late 20th century ). Use shellac as the sealer and start the nitro top coats, or cut it back and keep applying relatively thin nitro top coats. If you choose the latter, wet sand 400 at least between coats. You will get there eventually. Be grateful it is not a dining table or a run for a hotel or some such thing.
Go look at a brand new Gibson Les Paul custom shop, still a little of the grain telegraphing as they don’t let it cure long enough. Both my CS Les Paul’s do this. I have an R8 with VOS finish, and another custom/custom R8. In other words, have lots of patience, or just live with a little telegraphing. If you want to speed things up apply two coats of conversion varnish, wait a week and then cut it back smooth. Then go over top with your nitro. This will save about a month.
