Hairline Cracks in Macassar Ebony Back

If you have a string instrument of any kind that needs fixing, a mistake you made in building a new instrument that you need to "disappear," or a question about the ethics of altering an older instrument, ask here. Please note that it will be much easier for us to help you decide on the best repair method if you post some pictures of the problem.
Philip Secrist
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Re: Hairline Cracks in Macassar Ebony Back

Post by Philip Secrist »

I think I will try that first. Thanks a bunch Barry! :)
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Barry Daniels
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Re: Hairline Cracks in Macassar Ebony Back

Post by Barry Daniels »

You're welcome.
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David King
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Re: Hairline Cracks in Macassar Ebony Back

Post by David King »

I'll just say that CA glue can take a surprisingly long time to gas-off completely. I'd wait at least a week after a drop fill and I'll also roughen up the ca surface with 220 or 320 to get good adhesion. As it dries the CA will continue to shrink back so be prepared to drop fill with lacquer several times. This is good in a way because the CA always buffs out differently from the surrounding finish and you'll want to completely cover it up if you can.
Philip Secrist
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Joined: Tue Mar 06, 2012 5:24 pm

Re: Hairline Cracks in Macassar Ebony Back

Post by Philip Secrist »

Hey Barry. Trying to sand down below the excess CA and respraying didn't work. So, I think I need to take the back down to bare wood, start over, and refinish it. Just to be clear, you don't think that using a good clear epoxy like West System or SB-112 System III to attempt to fill any pores that didn't get filled well enough the first time or more importantly to fill any other cracks that I can't see that may be starting is worth the effort? Just trying to maximize my chance for success. Thanks!
Philip Secrist
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Joined: Tue Mar 06, 2012 5:24 pm

Re: Hairline Cracks in Macassar Ebony Back

Post by Philip Secrist »

Sorry to ask one more question. Now that I have removed the finish down to the bare wood, is there anything more I should do to address the cracks? (I filled them with CA on the finish side before removing the finish and also from inside). I cleated the cracks on the inside. Do I need to reapply grain filler and sealer coat again just like if I were starting at the beginning or can I just spray a wash coat of Shellac (also as a barrier coat) and then go on on to the build coats? Thanks
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Barry Daniels
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Re: Hairline Cracks in Macassar Ebony Back

Post by Barry Daniels »

If you sanded the finish off and didn't use stripper then the pores will probably still be filled. However, if you sanded into the wood some then the filler may have been removed. Get a magnifying glass and look carefully at the surface to see if you have open pores. If not, then apply your shellac and finish. However, if you used epoxy fill on the original finish you should probably use it again to allow the back to better match the sides.
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