lacquer woes, old & new

[Dave Richard]

Problem #1:  A customer's HD-28, from the mid-90's.  Several years ago he applied a Herco clear 'Top Pickguard', a plastic rectangle above the soundhole. When he removed it recently(a few years after applying), left behind was the disfiguring seen in the attached pics. I tried naptha(hoping it was the adhesive film residue), but no effect.  I think what I'm seeing is a melding of the adhesive with the lacquer, and is not removable(except by scaping/wet sanding/buffing, and unpredictable).  Anyone else dealt with this unfortunate issue?

Problem #2: On my recent acoustic build, I used Campbell brand rattle can nitrocellulose lacquer.  All went relatively well, waited two weeks after final coats to final wet sand & buff.  After 10 more weeks, the finish is apparently quite soft- leaving the guitar in the shaped, hardshell case results in imprinting of the 'fur' lining. Scratches too easily, seems to me.  My question is, to anyone with experience of a similar problem: will the finish continue to sufficiently cure/harden  relatively quickly, or is it as cured as it will get?  I know that lacquer becomes brittle over years as theplasticisers outgas or degrade, but that's not what I mean.

[Kerry Krishna]

Dave, I would be encouraging the Martin owner to be contacting the pick guard company, and possibly threatening a Lawyer. That damage, is just criminal. I have no help for you on possibly fixing it, so will keep my mouth shut.

 The soft lacquer no off gassing fast enough and lacquer being soft ... Well, I'd get the guitar back from the customer, and let the axe sit in your shop for a few months to safely off gas. It's such a huge drag too. Contact the manufacturer, and see what they have to say.    Frank and other folks here may know of a speed up process for this, but I don't.

 Good luck with both these projects...  

[Dave Richard]

Hi Kerry, fortunately, my latest build, with the 'soft' lacquer, is still in my shop(it's a spec build). So no unhappy customer...yet.

[David Farmer]

Problem #1 looks raised up from the surface. As though there is still some sort of backing adhered. Is it as hard as the  lacquer? There are lots of adhesive residues that are unaffected by Naphtha.

[Dave Richard]

Yes, it's raised, and as hard as the lacquer: I gingerly, with a sharp chisel, tried to separate the raised area from what's underneath, but they seem to be one & the same.

I'm not aware of what other solvent might affect or soften/remove the raised part, without damaging the lacquer itself.

[Glen H]

Have you tried a little sandpaper on it? I have no idea what that stuff is but could it be level sanded and buffed out?  Wild thinking here but could the finish outside of the guard have just shrunk?

[David Farmer]

There are few things I would less like to do than go through a pale burst finish like that.

If it’s the lacquer raised up then the color might be as well.

If it is not your problem, I would Let them puppies sleep! 

There are safer ways to make money.

I would pull out my Microscope out of curiosity though:)

[Frank Ford]

The finish on that sunburnt Martin may not be too bad an issue if it is actually as hard as the surrounding area.  I'd give it a fingernail test to judge relative hardness, and if it seems good, I'd try block sanding with 1200 grit, then buffing with fine Menzerna compound on the typical flannel wheel.

[Greg Mirken]

Before doing what Frank suggests, I'd have the guitar owner take the instrument back and wait 6 months or so. I think the guard and/or adhesive has caused the lacquer to swell underneath. If you level and buff now, the area might sink over time. And be sure he's aware it will never completely disappear.

[Dave Richard]

Thanks for all your replies- after discussion, the owner has opted to leave it be.  Just as well, by me.

Anyone have any thoughts on problem #2, 'soft' new-ish lacquer?

[Glen H]

Regarding number 2, the only way you'll know if time will cause it to harden/toughen further is to wait.  If it  were mine, I'd hang in somewhere to let it off gas for 2 months and check. Hang it where the humidity is correct.

[Robbie Collins]

The warmer the room and the lower the humidity, the faster it will off-gas. As will a breeze across it.

[Dave Richard]

I've got the guitar hanging, to allow for further off gassing...and hopefully, curing.