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Thread: Ebony & Lacquer

  1. #1
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    Help, Iím having a hard time getting the finish to work on the ebony headstock. I am spraying Lacquer (Deft) directly onto the wood without issues excerpt on the headstock, where I keep finding small bubbles in the finish. Is this common? The bubbles donít seem to appear anywhere else, only on the ebony. The bubbles donít seam obvious when applying the thin coats of lacquer but appear when Iím leveling (wet sanding). Another variable perhaps worth mentioning is that I have been laying the mando in my work space near a 60W work lamp to help with drying and discourage humidity. Not optimal Iím sure, but again the bubbles are only showing up in the ebony. Perhaps I need to apply a sealer coat to the ebony before applying the lacquer. This is now the second time that I have had to strip the headstock back down to bear wood. Your help/suggestions would greatly be appreciated.
    Sincerely,
    Prescott

  2. #2
    Registered User sunburst's Avatar
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    Different things can cause bubbles, and some of them look different than others. Can you get a pic? Probably not, if you've stripped it to wood again.

    Anyway, are they localized? Near the edges? Do they seem to be coming out of the pores in the wood? Are they tiny, or bigger?

    If they are more or less everywhere and evenly distributed on the ebony, a wash coat might help. Thin the lacquer to about half the usual viscosity, and spray a thin coat or two, let it dry, scuff with fine paper and procede. If you're using spray-can Deft, you might try a sanding sealer, or vinyl sealer on the wood. (I don't really like vinyl sealers, because I tend to loose clarity in the finish when I use them.)

    If the bubbles are along the edges, or distributed in discernable patterns like waves, you may be spraying the coats too heavy. If the finish is so thick that the surface skins over before the lacquer can "flash off" completely, the solvents can "blow bubbles" in the trapped liquid lacquer under the surface.

    If you are spraying the wood while it is cool, and then warming it with the light, that can expand the air in the wood pores and cause them to "blow bubbles" in the finish. If you warm the wood, do it before you spray, and let it cool gradually as it dries, or be sure it stays nearly the same temperature while it dries. The evaporation of the solvents tends to cool the work anyway, so just avoid heating the piece while it's drying.

  3. #3
    Formerly F5JOURNL Darryl Wolfe's Avatar
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    Might it simply be that the ebony is green with oil and moisture
    Darryl G. Wolfe, The F5 Journal
    www.f5journal.com

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    John has covered it well. I've had this problem from time to time as most of us have. If you keep spraying and sanding,the bubble problem will,in all liklihood,go away. I've been using water thin CA to seal small areas of Ebony lately and it works well,although a bit tricky. You have to apply a small pool of the CA and quickly spread it over the surface,keeping the spreader moving as in French polishing. Don't use your bare finger as you will get a quick heat flash and may wind up as an upgrade to your mandolin (I know this sounds foolish,but I did it once in a panic situation). Use a smooth piece of leather,plastic spreader, or a muneca. Don't use the blue chemical gloves. The CA will dissolve them in a trice.
    Jim

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    Thanks for the replies and great tips.

    Yes, I have striped it back down to wood, so no picture (though no camera either). The very fine bubbles do appear all over - So, I'll buy the idea that they are off-gassing from the wood. I will get a sanding sealer coat this time around - I think I actually saw a can of Deft sealer when I was buying the lacquer.

    For ebony that may be "...green with oil and moisture" - Would the sealer approach be appropriate in that case too.

    Your tips to avoid spraying thick coats or spraying on cool wood then heating are also good and I will be extra carefull on my 3rd time around.

    Thank you for your help.

    Prescott

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    Probably not a sealing issue. Probably heating the wood is causing off-gassing. Keep it at a constant temperature before and after spraying.

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    I'd probably also vote for the heating issue. I've experienced it spraying lacquer over any porous wood, especially like oak (not on a mandolin) if the wood is cool and then is warming for one reason or another after the lacquer goes on.

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