Problems when polishing cellulose finish

[Chris Richards]

Hi

Hope someone can help...... I always use nitro cellulose for finishing my guitars but just recently I've had some problems, not with the spraying but when polishing the final finishing, the end result is flat and shiny but I'm getting thousands of minute white specs it really does look like white dust, as you would expect it only shows up on darker finishes, earlier in the year I did a candy apple red which was affected really badly, certain areas were worse than others. At the time I put it down to a bad batch of lacquer, but just now I'm spraying a black guitar and getting the same problem albeit to a lesser extent....Any ideas?

[David King]

Is it minute bubbles in the finish that are filling up with polishing compound as you buff?

[Chuck Tweedy]

What finish are you using?
What is your schedule?
What are the conditions you are shooting the finish in?

[Chris Richards]

It's nitro cellulose clear lacquer, I don't have a spray both but it's shot in warm conditions outside, I leave at least a day between coats and there's usually no more than 3 coats of clear, then I leave it about 3 weeks before starting to polish it.

I certainly can't see any bubbles in the finish and when I sand it back they don't disappear. although if I wet the finish they don't show

[Michael Lewis]

That sounds like it may be tiny bubbles in the finish. The 'fix' is to prevent it from happening. It is probably caused by the spray gun being too close to the surface and applying the lacquer too heavily.

I found it better to let more finish through the gun and hold it about 9 or 10 inches away (c. 25cm), and spray to just get a wet surface and move on. It takes some practice and experimentation with YOUR equipment to get it sorted.

Take some sand paper to the little dots and they will sand away if they are in the finish.

[Chris Richards]

Thanks for the advice, It doesn't seem to be so bad with the new lacquer I have, I'll also try changing my spraying technique a bit and see if that helps.