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Polyurithain coating

Discussion in 'Luthier's Corner' started by Freaky Fender, Oct 2, 2003.


  1. I have a Squier maple neck I've sanded down to a fretless. I've picked up some clean Polyurithain, and I was not sure on how many coats I should use on a maple fretboard. My "guesstimite" would be 10 coats. Also, should I put lemon oil on before or after I put the coats on?
     
  2. Bass Kahuna

    Bass Kahuna

    Dec 3, 2002
    West Lafayette, Indiana
    Luthier, Custom Builder
    I'm assuming your refering to the whole neck, including the fingerboard, and you have already filled in the slots where the frets used to be, and are now dealing with a bare maple fingerboard and neck.

    How many coats of polyurethane you need will depend on how thick of a gloss finish you want, how thick you put on each coat, and how much of each coat you sand back before applying the next coat.

    Also, for a gloss finish like varnish, lacquer, or polyurethane, I would not oil the wood at all with lemon oil or any other oil first. You could put a sanding sealer on it and then block sand it down after the sealer dries to fill in the grain.

    Also, unlike lacquer, each new coat of polyurethane will not "dissolve" into the previous coat like lacquer does, and therefore sometimes when block sanding polyurethane down you will get lines in the finish where you break through the top coat into the coats below, so be careful you don't sand each coat back too far. Therefore, I would suggest thin to medium coats and steel wool between them to avoid breaking through the top coat.

    :^)~
     
  3. Word.

    If you're using a polyurethane from a can, be warned that it takes longer to cure than catalyst hardened versions. And curing is really needed to get the latest coat to a sandable stage. If you don't, you'll block up your sanding media (permanently I might add) and make a mess of the finish. The spraycan versions I've used (Verathane, Spar, and MinWax) have needed at least a couple of days to fully harden to the point I like.

    You can avoid this by sinking a lot of dough into spray equipment and popping 3 part acrylic poly onto your projects. Nothing beats the hardness this stuff attains.