pinholes in my nitro

[John Sonksen]

I've just buffed out my latest build and while the finish is overall very nice, it has on the surface the tiniest little pinholes. I used Behlen's nitro lacquer over their vinyl sealer, with some of the first coats being mixed with transtint colorants. The back of the guitar is Sapele and the face is Maple, and the finish is doing the same thing on both sides so I'm reluctant to think it had to do with pore filling. On the Sapele I pore filled with pore-o-pac after doing my sealer coats. The nitro was given two plus weeks to cure before I started my wet sanding and I started with 400 grit, moving up to 1200 before I started with Maguire's ultimate rubbing compound with a foam pad on a right angle grinder/polisher. (still haven't gotten my buffing wheels to do a mezerna setup). I didn't thin the lacquer when I sprayed it except a little in the color coats, and I used lacquer thinner.

Does anyone have any experience with this kind of thing happening, or offer any reasons as to why it did or how to avoid it? The pinholes are really small, to the point where I don't think I need to fix it, but I'd like to figure out how to avoid it none the less. The only thing I can think of is maybe I should have thinned the lacquer a bit or used a retarder to give me enough open time for bubbles to escape. I certainly didn't see any indication of bubbles in the finish while I was spraying and only stirred the lacquer before I put it in the gun, I didn't shake it at all.

[David King]

John, I'm wondering it they were small bubbles in the finish that you cut through to. It could be from the spray gun you used or it might be from pores bubbling out if the body went from a cooler environment into a warm spray booth just before you sprayed it.

[John Sonksen]

David, I think it had to do with the fact that I sprayed the finish unthinned. I'm trying to think of how hot it was when I sprayed, but I'm thinking it was on one of our warmer days. I normally reduce with lacquer thinner but I'd seen that a lot of people just go straight out of the can without a problem, and since the object was to build coats quickly it seemed to make sense. I think I should have reduced slightly as well as used a retarder to allow any solvents in the finish to off-gas before the surface skinned over. I did build a lot of finish very fast this time too, which really didn't help I'm sure.

I'm not concerned with the gun I used, it was a very nice nearly new devilbiss compliant gravity feed and it gives awesome results. I'm not sure I can do anything with it as it sits, or whether the fix would be that much of an improvement if I did try. It's really rather nice and I really don't have another two weeks to kill on it waiting to buff again.

I'll just have to put this in the old memory bank and remember not to do it again next time!

[Michael Lewis]

I had a problem like this with Cardinal lacquer, and found I was putting too much on and the gun was too close. I should have been about 9" - 10" away from the surface.

In warmer weather you need to thin for sure. The paint stores around here (northern CA) often sell seasonal thinner with more retarder in the warm weather and a hot quick flash thinner in the colder months.

[Barry Daniels]

This is called solvent popping and is a common lacquer application problem.