How to paint in higher temp and humidity

SDE · Jul 12, 2015

It was 78% humidity and 83 today. I thought I should not paint until it was less humid. I did some checking on line and found that if you use the correct reducer, you can paint when the mood moves you to do so. So if the reducer is designed for 70 degrees, should I paint when it is that temperature, regardless of the humidity? Or even if it is raining outside?
Thank you
Steve

Stephen Newell · Jul 12, 2015

The slower solvents are really only good when the humidity is borderline, not excessive. When humidity levels reach 70 percent it begins to blush. When the humidity gets up to 72 or 73 percent you can use a slower solvent and get away with painting. At 74 percent you may have some blush if you put too much paint on at once. At 75 percent and higher you need to wait until another day or have dehumidification equipment. What happens is moisture from the air actually gets into the paint and when it comes to the surface it clouds the finish. A slower drying solvent will sometimes allow the moisture to get out of the paint before it dries. Personally I don't care for these solvents. It slows the drying time down and also extends the amount of time the paint needs to fully cure and harden.

SDE · Jul 13, 2015

Thank you for the explanation. I will try to only paint when the humidity is below 70%.
SDE

dr sportster · Jul 14, 2015

I went to the PPG website and there is no mention of humidity ,only temperatures. If you search " humidity levels for auto painting" you only come up with advice from hot rod forums. Not much in the apllication guides about humidity. I know I've had it bite me.

glennster · Jul 14, 2015

also be sure you are running filters, and at the very least, moisture traps in your air lines. we have a large desiccant drier on our air lines here at the shop.

showcrop · Jul 14, 2015

I have ten feet of 3/4 copper and a drain valve off a drop before my regular water trap. It catches a lot of water, but the other day I was sand blasting and some moisture still made it through. I am thinking of a water tank arrangement to keep the pipe from heating up so quickly.

CNKS · Jul 14, 2015

My work area is 30x30 ft. The air pipes go around most of that perimeter. I have two water traps. The first trap is about 70 ft from the compressor, the one for painting is 100 ft away. I don't get any water from the first one, the second is insurance for painting. I live in a dry climate, but early in the day when I do a lot of painting, the humidity could be 80% up. I paint inside, exhaust fans pull the outside air in -- I have never had problems with humidity.

rustybronco · Jul 16, 2015

we have a large desiccant drier on our air lines here at the shop.

ne can home-brew their own unit for just a few bucks.

Not shown is the desiccant which can be had for as low as $16 a quart.

The gauge was used to check the pressure drop while testing my configuration. I replaced it with a 1/4" pipe plug so that I could check the desiccant's color from time to time.

Connect up the moisture trap first, then the oil trap, the dryer and finally the air line pressure regulator.

When the desiccant gets saturated, remove any plugs and bake it in an oven for a few hours to remove the moisture.

http://s32.photobucket.com/user/rustybronco/library/Dessicant%20dryer

How to paint in higher temp and humidity

SDE

Well-known Member

Stephen Newell

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SDE

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dr sportster

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glennster

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showcrop

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CNKS

Well-known Member

rustybronco

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