Circles in spray finish

#1

I have a strange issue applying polyurethane with my HVLP sprayer. When I spray, the surface looks smooth and wet and level. Soon after it begins to dry, I see small circles where it appears the finish is drying and lower than the remaining wet finish. The circles, although subtle, are visible in the dried finish. It looks as if it’s some sort of chemical reaction to dust, possibly pushing the finish away from the dust or perhaps the dust absorbing the finish, although the size of the circle looks larger than some invisible dust would be capable of absorbing that much finish.

Anyone familiar with this issue and a fix? I have one more coat and hope to resolve this for the last coat.

Thanks!

Jeff.

#2

Could be a silicon contaminate thats from rags or old finish, or the wood it self some need cleaning with acetone before glueing or painting.

#3

Hi Lou,

Here’s a picture. Do you recommend I wipe it down with acetone or mineral spirits after I sand and before the next coat of poly? Or should it be okay to blow off with compressed air? I’m new to spray finishes.

IMG_20200331_160949
IMG_20200331_1609492016×1512 1.08 MB

#4

Yes, Jeff sanding and cleaning is great. I would spot paint it to save your work of doing all again. Even if you have to brush the spot and then sand. These marks look like they could be finger tips with glue.

#5

Thanks, I’ll give it a try.

#6

I would wipe the surface with denatured alcohol before applying the finish.

If that doesn’t work, I would make sure your finish is not contaminated (oil from the spray gun?).

Gary A

#7

Thanks to everyone for feedback. I’m pretty sure this was fish eye from silicon. I had recently used silicon lube for my garage door opener screw which was just to the side of my projects and overhead. I think opening and closing the door was sprinkling it randomly.

It turned out that once dried, the spots were barely detectable and after final sanding and buffing, not really visible.

I’ll know to take better care in the future. Also, I found a additive product called Smoothie which apparently eliminates fish eye even with some contaminates in the mix. Evidently, a lot of guys doing car finishes encounter this issue and use the product.