Cracks In Laquer Finish

[olddog]

In an attempt to avoid nitro fumes, I painted an all mohogany guitar with generic hardware store clear laquer. That worked very well, so I suggested that to my brother as a finish for his hollow tele, which was mohogany with a 1/4 inch maple cap. It went well, but when he put it together, the maple developed several long stress cracks down the center of the body. Not really the maple, but the finish over it. He's a player, so it doesn't bother him much, but it bothers me. Is the laquer just to brittle for a guitar, too cheap, or possibly too thick. ( I thought I sanded enough off between coats, though ). For a fix, would it be possible to sand, and then lay another coat to fill the cracks, or must all the cheap laquer be removed and reshot with something more flexible?

[Doc]

It sounds like what is happening is that the glue lines are telegraphing through. Are the "cracks" only on the glue line? If so you just need to put more finish on it and sand it back down. The stuff you used is probably Nitrocellulose lacquer. Just an inexpensive low solids type. It has a tendency to shrink back pretty dramatically as it dries and show any inconsistancies in the wood.

[olddog]

Hey, Doc. These are like spiderwebs covering about a 5 inch swath down the middle. Hey, you're good. It is a Velspar, clear laquer, 7 bucks a quart. I didn't think it was nitro, but I just looked at the ingredients on the the can, and sure enough, it has nitro in it.

[Doc]

Thanks for the compliment.

Lacquer shouldn't be cracking like that unless it's pretty old. I've never seen that happen before, You have something strange going on. The only thing that I can think of is that maybe the lacquer is reacting with something else that you used. If you used a chemical stripper or a stain that isn't compatible you could have this happen i guess. What else did you do? Stain, stripper etc. I'm really intrigued.

Valspr is a couple of steps up from the usual paint store stuff.

[olddog]

Hey, doc. I put a couple coats of behlin vinyl sealer over a behlin solar lux red stain. At least to me, it doesn't seem like a compatability issue, because the mohogany is fine. All the cracks are radiating from mounting points, the bridge, the pickup rings, all radiating toward the neck pocket. I think I know what you're saying about the cracks following the glue joints, and the grain of the wood, but these cracks seem to be going from screw to screw, with no respect for grain. Kind of like a crack in a windshield. But all that being said, I got to ask you this , doc; what kind of clear would YOU put on a bare mohogany guitar . I respect your expertise. ( Just don't say french polishing, I learned enough about it to find that I can't do it. ) Thanks, d

[Doc]

I like Deft. The spray cans do a good job. It's a type of nitrocellulsoe lacquer. It holds up well. It sounds good (to my ear) on acoustics. I've got an olf Epiphome that I redid in '75 with it and it looks and sounds great.

The stuff is a little soft as far as lacquers go, but its easy to rub out.

Vinyl sealer is weird stuff. It does build fast, and there are times when it will seal stuff that nothing else will, but I've also had jobs go to hell in a handbasket and the sealer seaemed to be the culprit.

Lowe's sells the rattlecans of Deft. Also their sanding sealer. Don't use the quart can stuff over anything but stain. It is a brushing grade lacquer and the slow dry solvents will pull a lot of sealers.