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painting in high humidity
#1
I need to finish painting my engine bay but humidity has been 75%. I can put a dehumidifier on in my garage before and after I paint but opening the garage while painting is may concern. I'm spraying Eastwood extreme chassis black which says less the 50%. Any inputs from the painters on the forum would be appreciated. What could go wrong?
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#2
You could bring it to my garage. It's only 20% humidity here! Big Grin

- Travis



I'm an analog man in a digital world.
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#3
Doug The Dog;187348 Wrote:You could bring it to my garage. It's only 20% humidity here! Big Grin

But isn't it 110 degrees too. The paint has a temp limit also Big Grin
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#4
I finished a job late one time and the water started condensating on the passengers door of my old SVO. That part of the clearcoat ended up having a milky look to it when it dried because the water made tiny bubbles which distorted the finish. They were deep too and would not color sand out. Had to refinish the door.

Mike
__________________________________
Black 1985 GT
Yellow 1973 Mustang Mach 1
Black 2012 5.0 GT, 6-speed, Brembo brakes, 3.73's
Wimbledon White 1966 F-100 Shortbed Styleside, 390ci, Tremec 3550, FiTech EFI
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#5
Hi Jim,

In Australia, we can't buy Eastwood products. However, i looked up Eastwood's extreme chassis black on the net,and could not find mentioned anywhere if the product is a fast dry single pak enamel or is an acrylic lacquer product. I assume you have chosen the satin black and not the gloss black, and you have bought the aerosol not the tin of paint as such.Would that be correct or not? There are performance differences with using those different products as such. Anyway..................................................

SO, WHAT COULD GO WRONG?

A few things for sure. 75% humidity is not good for spraying conditions. All auto paints DON'T like to be sprayed in humid conditions. You will find that lacquers play up the most with humidity, followed by quick dry single pak enamels, and then 2pak enamels least.Three basic things can happen when spraying in humid conditions. 1. The paint film can loose it's durability in relation to wear and marr resistance, and gloss retention 2. the paint film's ability to adhere to the substrate properly is compromised and can lead to paint not sticking properly to the surface you are painting over, and 3.The final finish or appearance of your paint is compromised.Humidity blistering can appear from nowhere on the surface of your finished coat. Blushing or blooming of the finished coat can be visible on the paint finish. Moisture in the air settles on the paint and penetrates into the film as you apply the number of coats. Extreme moisture can ruin the appearance of the finished coat too, with moisture bubbles appearing randomly.Later in time humidity blisters can appear from nowhere on the finished surface because of trapped moisture in the paint film. Complete sanding and removal of the blisters, and then refinishing again, is the only way to rectify that problem. If you are using a spraygun and have mixed your paint from a paint tin, make sure there is zero moisture coming through your airline, as this will cause major probs like humidity issues as well.

SO WHAT ARE YOUR OPTIONS?

The easiest approach would be to wait for a less humid day to spray, and spray in the middle of the day when the outside ambient temp is at it's hottest. Don't spray on a rainy day or on cold rainy days as this creates humidity probs as well. Pre heating first and post heating panels after spraying can remove the humidity problem too.That gets rid of the blushing appearance as well. Use infra red heating lamps and/ or a powerful heat gun for that as well. The lamps can be hired from hire shops if you don't want to spend money on tooling up. Also, spraying a light coat or two of thinners, or better, retarder thinners or 2pak reducer over the final coat of black that has just come off the gun and is flashing off, and is blushing, can draw out the moisture and remove the blushing look as well.Blushing or blooming takes on the appearance of a whitish dull looking frosty film on the finished coat.Once blushing is locked in on the final finish, and your paint is dry, refinishing the effected panels again is the only remedy. The BEST OPTION would be to hire a spray booth, where the spray temp can be controlled, and humiity probs totally eliminated. I don't know much about your dehumidifier gizmo, but be careful of paint fumes building up in your shed whilst spraying and using appliances at the same time.

Spraying a 2pak premixed satin black enamel is a great choice of paint to use, in a engine bay. It offers the most durable finsh in relation to chemical, heat, scratch and chip resistance and is least susceptable to humidity issues when spraying. Some guys even like to use epoxy paints for engine bays as well. Lastly, make sure you use the right type of primer under you black topcoat for good adhesion and corrosion resistance. Be aware also, that primers and putties can fall victim of humidity issues as well as topcoats.

Hope all that helps,

Regards, Greg.Smile

(Pro spraypainter)

whistling LORD, MR FORD - JERRY REED
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#6
Greg,
Thanks for the write up. I'm not using thier spay cans. I'm using third quart mixture. It doesn't require mixing a hardner. The weather calls for Saturday to be 64% so I might experiment with the dehumidifer and heater to see what happens. Spray a test panel first.
Jim
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#7
I've sprayed 7 cars with both single and 2 stage paints, in 100% humidity, with no problems.
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#8
mach1chick;187413 Wrote:I've sprayed 7 cars with both single and 2 stage paints, in 100% humidity, with no problems.

You painted in the rain? Huh Big Grin
-or when the air was 100% saturated...? Smile

Ray

1971 Boss 351  
1972 Q code 4 speed convertible 
1971 Mustang Sportsroof  351-2V FMX 
1973 Mach 1 (parts car)
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#9
Lol! Sometimes feel like it here in Western PA.! But yes, humidity is usually around 100%. Hard to breath sometimes.
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#10
MeZapU;187359 Wrote:I finished a job late one time and the water started condensating on the passengers door of my old SVO. That part of the clearcoat ended up having a milky look to it when it dried because the water made tiny bubbles which distorted the finish. They were deep too and would not color sand out. Had to refinish the door.


Had the same crap happen to the hood of my truck ruined the paint job. Still have to redo it.
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