Painting in high humidity

[Buick35]

I live in Florida and have a non air conditioned garage.I plan on painting my car sometime this summer. What tips do I need to know when painting in high humidity and heat? Urethane single stage paint. Thanks. Greg.

[PFitz]

Good quality urethane single stage paints are more forgiving of damp shop conditions than lacquers are.

 

Make sure your compressor system is not adding moisture to the spray mix. There's lots of info online how to prevent that and it doesn't need expensive gadgets added to your compressor/air delivery system.

 

PPG says that dampness in the air, and slight amounts on the surface to be painted, won't hurt, it actually helps to cure their DP40 series epoxy primers.   And when it's cold and damp you can add 5-10% lacquer thinner to the DP40 to help it flash off between coats. 

 

For sanding primers and top coats, use a "slow" (warm shop) temp reducer and spray light coats. Don't get in a hurry and try to get full coverage with each coat. Whenever it's high humidity, allow 10-20 minutes more time between coats for the solvents to flash off. Urethanes have a longer "open coat" time than lacquers so, even waiting 35-45 minutes between coats, it will all blend fine.

 

Worst mistake you can make is to get in a hurry to get the paint on ! 

 

Paul  

[Digger914]

Nice thing about high humidity is that it helps to settle dust and heat is also good, but there is that old saying to much of a good thing.......... Good advice from PFitz and only adding a few simple things.

 

Tips: If you don't have a dryer for your airline, get an extra length of air hose, coil it up in a 5gal bucket  filled with ice and enough water to cover the hose. Depending on temp you may need to refill this bucket several times so keep an eye on the ice level. Put a water separator up near the spray gun, one that you can see into so as to know when it is getting full (I use a drainable separator) and use both fish eye and hardener additives.

 

Watch out for sags and runs, easy to fix when wet but it does take some practice, suggest practicing removal by creating runs and sags on some old panel to test how well your paint holds in the temp and humidity of your paint day. Get a good clean shop rag dampened with your reducer and dab off the runs you create to get a feel for the touch you might need to use later.

 

A cold beer and a good cigar doesn't help the paint set up faster, but it will help pass the time between coats. Lots and lots of light coats before you lay down the heavy shine coat and have fun.

[joe_padavano]

Well, for all the time and money you are planning to put into this paint job, why not buy a dehumidifier and run it in the garage prior to painting?

[Bhigdog]

Hopefully i won,t be painting any more cars but i always waited for a low humidity day. Always took a shower and used no deodorant. Always used fish eye killer. Floor was wet mopped the day before but dry for painting. Wife knew not to talk to me on paint day.

Never had a water in air problem but picked up a perfectly servicable 50 CFM refrigerated air dryer on ebay for $50. End of moisture problems. Before the dryer i actually had air tools freeze up with ice.....bob

Edited May 4, 2019 by Bhigdog (see edit history)