Humidity while painting

[DanB]

Can someone tell me what the highest humidity percentage would be to still paint the Polly products? We are at 68% right now and I have blush retarder on hand...Just didn't want to spin my wheels.

[RandyL]

I haven't shot Aerothane yet, but I can tell you that 68% humidity would be no problem for PPG urethanes. I suspect it's fine based on the comments from their web site below...

APPLICATION PROCEDURE: Spray a light color coat, enough for gloss and color, but not enough to run. WAIT until this coat is tacky and transfers no color to your finger. Should take 20 minutes at 77°, longer at cooler temperatures. Don't let this first coat dry completely. Spray a medium coat of paint. This coat should flow out and look wet; again don't flood it on. Now spray a final wet coat for fill and color. Do not flood it on! That's a total of three coats, wet, but not enough to run. These are normal coats, not cross coats. Dry film thickness should be approx. 1.7 mils (.0017). Application in less than 55°F. temperature is not recommended. Do not spray in ambient air temperature above 95°F. due to accelerated polymerization caused by the heat, resulting in reduced gloss. Relative humidity above 80% accelerates polymerization and may reduce gloss if exposed before drying 12 hours.

[DanB]

Thanks Randy,
Was looking for the info in the book and didn't think to check online. I had a full enough day eating turkey, sanding the wing, and mixing together the 5 gallons of yellow paint. I still have one coat of polyspray, then white, then the yellow. The shaker came to the rescue so no humping it to Home Depot.

[RandyL]

Dan,

Are you putting on a coat of white Poly Tone so that the yellow will show better? How are you measuring humidity? I never worried about it when painting my RVs and no issue with it. Maybe Aerothane is more sensitive to it.

[DanB]

I'm actually doing PolyTone for everything. Using the white PolyTone before yellow is suggested as it may be too hard to evenly cover the silver coat. To measure humidity was just looking at the nearby Gateway Airport weather. I've decided to jump into spraying tomorrow and will report on what happens.

[RandyL]

Pics Dan, we need pics!

[n85ae]

I painted my entire plane white polytone, and then painted it with Aerothane.
Aerothane is very easy to paint with just a little practice. The runniness
is not different than any other paint. In my experience, fear of runs causes
more problems than anything else, since you tend to underthin, and then you get issues with orange peel.

Here's a shot of my wing during painting:
http://www.aselia.com/n85ae/jeff026.jpg

After looking over Bruce Lina's plane, and despite that my Aerothane came
out as well as it did, were I doing it again I would just stick with Polytone
like Bruce did. It looks good, less shiny, but just as good in it's own way.
Plus a LOT less hassle.

MUCH harder is painting System Three WR-LPU, as I am using to paint
my CH801 project. It's a waterborne polyurethane, and very cranky to
use: http://www.aselia.com/ch801/img2356.jpg It does have the
nice feature that it's low toxicity, and you can drink the solvent.

Regards,
Jeff Hays

[DanB]

Well, no photos today... seems this was not the day to lay down paint due to several things, but mostly one thing:
Operator error...
I have been very meticulous about cleaning the gun to the extent of taking the air cap and needle valve out and soaking in solvent in between spraying times. That being said, I got things set up to spray today, did my test spray on cardboard and went to the wing. The spray pattern started then stopped within 15 seconds (nuthin but air). I went back to the bench, took the gun appart and cleaned it inside and out. Found out that the screen filter in the bottom of the cup can clog up with gunk even though it looks clean from up top. Cleaned it out good and was sure that was it. Put the paint back in, went to paint, same thing. I finally found that the little air hole in the lid of the cup was clogged. After that, the gun shot fine on the cardboard. By this time I was close to the end of my rope.

The humidity was only 50% and Temp. was a nice 70 degrees. I figured I was in a safety envelope but I still crashed and burned. When I went to spraying, I was introduced to two things I have read about but never met personally... As soon as I sprayed I got orange peel and fish-eye at the same time. I may have had the pressure turned down a bit too much and that probably gave me the OP. The fish-eye is what surprised me because I wiped down the surface with the 2210 prep solvent. I also have an in-line filter right at the gun. I may need to replace my filter and perhaps my hose...at any rate I'm offically calling it a day. Time to go to a movie with the wife.
Cheers

[DanB]

There is alot to be said about puting things down and walking away when everything starts going south. Today I walked into the shop and after sanding the boo-boos out from yesterday...I laid down the last cross-coats of Poly Spray in the morning.

silver1.jpg

silver2.jpg

After drying I went after the white Poly Tone which is suggested prior to shooting either yellow or red. I decided to try a trick that Alan Nephews told me about. He said before shooting the color coats, put the paint into the freezer...it doesn't freeze but keeps the paint cool enough to dry slower and gives a glossier finish. The pictures you see below show not a wet coat but the resut I was hoping for with a glossy finish. If you look close enough you can see some tiger stripes, but I was only going for a light coat of white (as per the instructions). I did not cross coat it, so this is encouraging to see even this coat gloss up. The Temp for this was right around 70 and the humidity at 50%. I used the 8500 thinner reducer.

white1.jpg

white2.jpg

Will do the yellow tomorrow.

[RandyL]

Dan,

Nice looking work! Your shop lights look nice too -- I'm sure by now you're glad you took the extra time to put them up. One thing I found me when painting same color coats on top of each other is to keep a small flourescent shop light in my other hand and position so I could see exactly how my paint was going on with the other hand. Might help you when you're putting yellow on top of yellow for example.

Keep up the good work!