Paint and Humidity, a lesson in patience

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mccoy300

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I tried to beat the rain the other night when painting the nose cone on an upscale 3” quest mean green… Tamiya TS paint is not a fan of humidity, and it caused bloom on the entire surface. Maybe next time I’ll be a bit more patient and wait 48 hours instead of being a boob. Anyone else ever feel the burn of trying to shortcut something while knowing the consequences?
 
I tried to beat the rain the other night when painting the nose cone on an upscale 3” quest mean green… Tamiya TS paint is not a fan of humidity, and it caused bloom on the entire surface. Maybe next time I’ll be a bit more patient and wait 48 hours instead of being a boob. Anyone else ever feel the burn of trying to shortcut something while knowing the consequences?
Oh, that's never happened to me. Never. Over a half-century of rocketry and I've never taken a shortcut while knowing the consequences of failure. I'm lying through my teeth, at least through the ones I still have... 😁
 
All the time. Even when I think/know the paints are compatible. Drives me nuts.
 
When I feel impatient and it's too humid outside, I just lug out my dehumidifier and plug it into an outdoor outlet and use the warm dry air on my rocket to help it dry faster...and properly.
 
I would say you guys in Az have it lucky… but those summer temps, no thank you
 
Done that a few times trying to get something done for a launch. Good news is that some 1500 grit will remove the top layer and one more coat will make it good as new.

I just had to learn that it was ok to fly naked.
 
I live in Florida. If I plan on painting that day, I will watch the local weather underground website and wait until the humidity drops below 60%. Usually sometime in the afternoon, before the showers. I get satisfactory results.
 
I hate paint PERIOD

So I prepped a new fiberglass nosecone.
1. Washed the nosecone with Dawn
2. I sanded the nosecone with #600 wiped it down with a wet rag and let it dry
3. I sanded the nosecone with #1500 wiped it down with a wet rag and let it dry
4. I painted the nosecone with Krylon White Primer. I gave it three coats, 2 minutes apart
5. I sanded with #1500 and wiped it down with a wet cloth and let it dry
6. I painted with Krylon Fusion Gloss Black, 3 coats waiting 5 minutes between coats

The first coat of black revealed these pinholes. Any suggestions? Is there better paint? It's not worth repainting, I'd just like to avoid this in the future.

Temp 72 degrees
Humidity 38%

Thanks!!
 

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I thought with spray paints typically pinholes are from thin application, but I could be wrong.
 
The primer did fine.... It's like there were tiny spots of oil that repelled the paint itself. I have read a few other posts and have a game plan for the next time I paint.
 
3. I sanded the nosecone with #1500 wiped it down with a wet rag and let it dry
4. I painted the nosecone with Krylon White Primer. I gave it three coats, 2 minutes apart
5. I sanded with #1500 and wiped it down with a wet cloth and let it dry
Humidity 38%
!
This has been debated before on here in several times, as there are lots of people who say that 1500 ends up making the surface way too smooth and there's nothing for the paint to bite into. Anyone in the auto body business would not go anywhere near that grit. 600 is even shunned.
I wish I could see humidity that low here.
Edit: I don't ever go beyond 320
 
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This has been debated before on here in several times, as there are lots of people who say that 1500 ends up making the surface way too smooth and there's nothing for the paint to bite into. Anyone in the auto body business would not go anywhere near that grit. 600 is even shunned.
I wish I could see humidity that low here.
My father owned a body shop long ago but I don't remember what they used. I would think nothing beyond 400 though. I don't even go that high with my rockets. Also, I wipe off the surfaces with rubbing alcohol before painting to remove oil as well as dust.
 
I agree with the others about sanding primer; no finer than 400 grit.
Wipe down with alcohol before painting and don't touch with bare hands.
I like SEM primer surfacer; comes in gray or white, fills great and sands easily.
Here's two I painted recently with Krylon Fusion like you are using;
Skyshark rocket 2.jpgSuper Mars Snooper finished.jpg
 
I don't think I would go all the way to 1500 on the sanding. That is a bit too smooth for color coats. I typically stop somewhere in the 600-800 range depending on the surface.

As for the spots, that is some type of oil, grease or even soap on the surface. My guess is that step #5 where you wiped with a damp cloth had something on the rag. For the final wipe down I'll use a microfiber towel but a quality shop towel / paper towel will work just as well with 91% alcohol on it and be sure to keep you hands off the surfaces to be painted. Typically my cones are on some type of rod or if the shoulder is long enough I'll mask and hold it that way.
 
I don't think I would go all the way to 1500 on the sanding. That is a bit too smooth for color coats. I typically stop somewhere in the 600-800 range depending on the surface.

As for the spots, that is some type of oil, grease or even soap on the surface. My guess is that step #5 where you wiped with a damp cloth had something on the rag. For the final wipe down I'll use a microfiber towel but a quality shop towel / paper towel will work just as well with 91% alcohol on it and be sure to keep you hands off the surfaces to be painted. Typically my cones are on some type of rod or if the shoulder is long enough I'll mask and hold it that way.
I'll try the alcohol next time. Thanks!!
 
I was a car painter. The small spots that the paint moves away from are called fish eye. That is from contaminants on the surface. Buy wax and grease remover, use 2 paper towels one to put on one to remove. 91% alcohol has water in it and ? I find that alcohol can brake down the primer.
 
I was a car painter. The small spots that the paint moves away from are called fish eye. That is from contaminants on the surface. Buy wax and grease remover, use 2 paper towels one to put on one to remove. 91% alcohol has water in it and ? I find that alcohol can brake down the primer.
so what is your recommended highest grit? 320?
 
400 to 600 on solid colors and 600 to 800 for metallic. Try and stay in the same series of paint. Just because its Krylon Colormax and Krylon Fusion are different formulas. Fusion and the Dupli color line work well together. SDS PDS have the formulas and safety use in detail.
 
I thought with spray paints typically pinholes are from thin application, but I could be wrong.
Pinholes can occur for a couple of different reasons. Surface contamination is most common - the surface tension of the paint pulls the paint away from the dust mote or oil particle = pinhole. Another reason is when the paint film is thinner than the surface profile. Say you have a 2 mil surface profile, but only spray on 2 or 3 mils of paint. Surface tension will pull the paint away from the microscopic "peaks", and you will get pinholes. This is a common source of rust bled through paint when painting steel. Water based paints have much higher surface tension and thinner films that old school oil enamels, so surface cleanliness is super important with water based paint.
 
pin holes in auto body are from the body man inducing air bubbles into the bondo or off gassing from the last coat of paint. tac cloth between coats don't rush let it dry. remember primer is not water proof. moister can get to the tube or be held in the primer. i stay away from wet sanding unless its a fiberglass air frame. epoxy primers are water proof but made no sense for a rocket finish. take your time.
 
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