Hot spots in lacquer

How do you handle them? January 21, 2002

What's the best way to handle hot spots? Should I wait for the spots to dry completely before shooting over them? I'm using N.C. lacquers. I have found that shooting ML Campell WW vinyl sealer over the piece solves the problem--is this recommended? The thing I don't like about this vinyl sealer is that it is hard to sand and I always get a milky finish. My finish process is to seal with Nitro sanding sealer, then coat with water white gloss (which is when the hot spots usually crop up), then top coat.

Forum Responses
I use a clean cotton rag, wet with water and wring out completely till damp. I lightly wipe over the shiny area, being careful not to damage the surface. Usually this will dry the spot.

From the original questioner:
How does water dry lacquer? A while back, someone told me that they hit the spots with ice water. I guess I'll give it a try.

I thought the WW vinyl Campbells sealer was one of the easiest to sand, as compared to other vinyl sealers.

From the original questioner:
That's what they claim, but I don't find it easy to sand and I don't see how they can call it water white. The only time I use it now is to cover the hot spots. I had three pieces this weekend covered with wet spots that stayed wet overnight. The next morning I shot them with the Campbells vinyl sealer, which eliminated the hot spots, then I sanded with 320 just to knock out the nibs and topcoated and they look great aside from a slight milkyness in two of the darker pieces, but they'll pass.

WWVS is not the best choice for darker colors. It is a good choice for pickle or light colored stains. If sprayed over dark colors, you will see a milky haze. This is due to the coconut resins added for a less amber finish. I have only found it hard to sand if it wasn't completely dry.

I don't understand your process, though. You said you used a nitro sealer, then a water white gloss (this is where problem occurs), then a topcoat. I think if you eliminated the nitro sealer and used 2 coats WWVS, then the WW gloss (Klearplast) you would get better results. WWVS has less nitro in it to begin with--that is some of the reason it needs to dry completely to sand better. Always spray 4 to 5 wet mils. If too heavy on the wet mil, the evaporation time is longer for the solvents to escape. Keep using 320 grit paper between coats to scuff sand. This will allow each coat to melt into the other.

Lisa Gilbert, forum technical advisor

One way to cure hot spots is to use VM&P Naptha on a rag. This will cook the wet finish and "set it".

Bob Niemeyer, forum technical advisor