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I have a 1980s Yamaha acoustic with a broken headstock. It appears to be cracked all the way through yet I can't get it to open by hand. I'm going to try to open it up with some clamps on the bench. Once I get it glued and clamped there's the finish touchup. Any idea what was used on these?

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Hutch

Get the heck off the couch and go build a guitar!!!!

Probably polyester. I have touched them up with super glue or lacquer, but there usually is a witness line, unless you spray the whole neck.

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John

I just want to touch it up. I told him it will show a little.

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Hutch

Get the heck off the couch and go build a guitar!!!!

This might be out of sync, but clamping the break and then flowing in thin CA might do the job. That stuff has no surface tension that I've ever witnessed.

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Peter Havriluk

If you can crack it open slightly you can introduce thinned Tightbond with a syringe and needle and blow it in with compressed air at around 10psi or so.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

I would use shellac.

If its polyester shouldn't I use that? I have some em6000 that may work and would be my preference.

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Hutch

Get the heck off the couch and go build a guitar!!!!

Isn't EM6000 a water based acrylic lacquer? Polyester is a catalyzed finish. Catalyzation is done either with a toxic chemical or high intensity UV light. In any case, I have no experience in applying EM6000 or polyester. My main concern when doing touchup is bonding, and CA or lacquer bond reasonably well. Shellac should also be compatible. Actual melting in of polyester equires a specialized solvent that is extremely toxic.

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John

I couldn't get the break to open so I'm assuming someone glued this and the owner wasn't told. It's a family hand me down. So I just scraped the loose finish and started drop filling the lines with CA. I just want to smooth out the mess and buff it without applying any finish.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I couldn't get the crack to open so I just repaired the finish with thin CA. I figure if there is a real split, the CA will find it way in there. I didn't need to do any finish work other than leveling the CA and you can't tell the difference between the the original finish and the CA, zero witness lines. I was amazed. The customer was very happy with it as well. It's smooth to the touch but I made no effort to hide the cracks. That said I wonder if I could add a little dye to CA for this stuff.

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Hutch

Get the heck off the couch and go build a guitar!!!!

You da man!

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"Act your age, not your shoe size" - Prince

Please feel free to offer up any suggestions for a better outcome.

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Hutch

Get the heck off the couch and go build a guitar!!!!

I suspect a lot of that thin CA made its way into the joints; it goes everywhere it can find a molecular opening for itself.

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Peter Havriluk

Would a gel or medium CA be better for the final drop fills? I didn't have any so I just continued with the thin.

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Hutch

Get the heck off the couch and go build a guitar!!!!

In my experience, you can use a medium gel for really big voids - but in general, thin is best. Might take time, but it's still faster than touching up with lacquer or shellac. I've experimented with TruOil for large surfaces when retouching, and I like it. Puts a nice gloss on when buffed.

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"Act your age, not your shoe size" - Prince