Paint spots on gas tank

Ted

Ted

Member
I had to restore another gas tank for our 29 A. I used the same laquer that I painted the car with 30 years ago but put clear on top. I put 3 coats of clear on at one time. I thought they were heavy enough. My problem is now that I have started wet sanding with 1200 grit paper I have some light areas showing up. I'm not sure what they are as I don't recall seeing them before the clear was sprayed on. Does anyone have any thoughts on what they might be? Thanks.
 

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Wet sanding fresh lacquer? Likely blushing from moisture absorption during wet sand or residual moisture in the old lacquer. This happens when you hit a lower layer that wasn't fully flashed off prior to applying subsequent coats. It may go away with some application of radiant heat (lamp) for about 30 minutes. Watch the temp, don't let it get too hot to touch. If not, you will need to re shoot color on that panel. Clear lacquer on furniture is notorious for getting white rings from wet glasses left on overnight.
 
Not sure if it would be old paint. I was more inclined to think it may have been from when I wet sanded the color before putting the clear on. I may have sanded through one of the color coats. I know this happened when I originally did the car. I thin each following coat just a little more than the previous to get a smoother finish & since the mix is not the same, the color shows some spotches. That was why I used the clear...to avoid that this time. It never showed like this when I painted our black Tudor.
 
It is called blooming.

Cold and moisture.

Lacquer flashes off using the air's ambient temperature.

Too cold and/or too much humidity creates moisture on the paint's surface.

I bet you will have to colour it again.
 
I bought a bunch of paint in the winter several years ago for the Coast Guard and by the time it got delivered from Georgia to Florida it was all destroyed because the temps were too low. The vendor ate that one!

Jack
 
I've had the blushing problem before. With that I usually wet sanded & polished & it looked fine. The tank was painted over a month ago when our weather was warmer but that doesn't mean the humidity didn't have an affect on it. I usually go by a cheap humidity gauge that I have. If it's over a certain point I don't paint.
 
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