Krylon Ultra Flat Black freakiness

[illini]

I sprayed Krylon ultra flat black over a coat of Krylon glossy white. As the black was drying, it shrank and formed cracks to expose the white. The black areas are now lumpy and nonuniform from the cracks. Spray again...same result. Anyone experience this?

What's the cause?

What's the fix?

What's the frequency, Kenneth?

 

Illini,

I had the problem you describe last night when I applied the Krylon Ultra Flat Black on the simulated reactor vanes of my Vector-V clone - it shrank and cracked, exposing the Krylon silver beneath. A second coat helped, but it still looks shabby.

Never had this problem with Krylon before.

 

[illini]

Me either. I wonder if Krylon semi-flat black would work better?

 

[Austin]

I use glossy on just about everything these days, then flat coat it. The glossy is thicker and can film right over slight imperfections.

Carl

 

[illini]

Originally posted by CTulanko
I use glossy on just about everything these days, then flat coat it. The glossy is thicker and can film right over slight imperfections.

Carl

Good plan. I'm chucking the ultra flat.

Funny thing about it. When sprayed directly on an unpainted surface it seems to work fine. Sprayed over a glossy coat...HOSED!

 

[DJ Delorie]

When mixing paints like that, you have to be very careful about the recoat times. Either do it right away, or wait a week for the base coat to REALLY dry.

 

[rabidsheeep]

same thing happened when i painted my skateboard, but it actulaly turned out pretty awesome looking

 

[wwattles]

Same thing happened to me when I tried to put a krylon flat black over a Fusion (plastic paint) red. Ended up stripping off both and starting the black from bare wood.

WW

 

[dragonshiprider]

I have had all sorts of problems with Krylon paints this summer.The only problems I had with cracking where not with Krylon,however.It was with John Deere yellow.Fact is that I was building an Estes Firestreak.Rather than go with the box cover purple job I decided on my own J.D. yellow with red flames scheme to match the red and gold streamers.I then used the stock decals to make a template for the word FIRESTREAK which I painted on.
Well everything was going fine until I decided to use some Dutch Boy clear I had laying around to top off the whole thing with.Wrong answer!This stuff immediatly shrunk up so tight that it pulled the yellow and red both apart.It wound up looking like a textured ceiling.I have since stripped the whole thing down and have re-applied the yellow.The red has yet to come.
Anyhow the problems that I had with Krylon where blushing under high humidity.The reason that they do that,in a nutshell,is because they are hot paints.When they leave the can they heat up(hence the ultra fast drying) and draw moisture to them.The solution is simple:Switch to Rustoleum.I have and have never been happier.Their gloss red is by far the most awesome I have ever seen.That's not to mention that they have behaved perfectly

 

[sandman]

It was with John Deere yellow.

LOL!!! Same color...same prblem!

who'd a thunk it?

 

[dragonshiprider]

Originally posted by sandman
LOL!!! Same color...same prblem!

who'd a thunk it?

I was hoping it would come to me but I reckon not.I'm lost and I don't get it.Did you have problems with your Apogee?

 

[BHP]

My understanding of why rattle can paint blushes in high humidity is because the cooling of the compressed gas/paint exiting the can reaches the dewpoint. You are effectively making dew on you new, wet paint.

When you paint in air that has a lower dewpoint the cooled, expanded gas/paint does not form the dew because the temperature does not lower to the dewpoint.

I can't explain why Rustoleum didn't blush for you but I'd assume the atmospheric conditions were not same. All gases cool as their pressure is lowered just as they warm when compressed.

But the bottom line is, as always, do what works for you. I like Krylon myself.

 

[dragonshiprider]

Originally posted by BHP
My understanding of why rattle can paint blushes in high humidity is because the cooling of the compressed gas/paint exiting the can reaches the dewpoint. You are effectively making dew on you new, wet paint.

When you paint in air that has a lower dewpoint the cooled, expanded gas/paint does not form the dew because the temperature does not lower to the dewpoint.

I can't explain why Rustoleum didn't blush for you but I'd assume the atmospheric conditions were not same. All gases cool as their pressure is lowered just as they warm when compressed.

But the bottom line is, as always, do what works for you. I like Krylon myself.

O.K. first thing;No it was pretty much the same all the time......humid,humid,humid.That's not exagerating at all.Like I told someone else;since I don't have the luxury of a booth or anything like that then it's either switch paints or wait until it's low enough humidity to paint.The problem with that is that when the moisture is that low i'll be too busy fightin' off tha Polar bears to paint.Welcome to Va.! Anyone at NARAM this year?
Now secondly I'll just go ahead and post what was told to me by one Mr.Doug Sams before I make an even bigger fool of myself than I already am trying to explain it:

"As others have said, it's the relative humidity. When a
compressed gas is allowed to expand, it absorbs heat. In
a humid environment, condensation will form due to this
cooling effect, and that condensation will cloud your
paint giving you a dull finish. Hot solvent enamels such
as Krylon and Testors as well as lacquers tend to do this
more so - the hot solvents tend to evaporate more quickly
than regular oil-based enamels.
The hot solvents have the nice feature of quick drying,
but at the expense of a dull finish (when the humidity is
up). Get some RustOleum (regular, not Painter's Choice)
and your blushing problem should go away. I've also had
good luck with Boyd's, which appears to use a different
formulation than its sibling Testors.
I got a hygrometer for my garage a while back. Last night
it was pushing 70% RH, so I opted not shoot any paint at all.
50% RH is OK for RustOleum. I haven't determined the RH for
Krylon and Testors yet, but I'm gonna try some next time it
gets below 40% RH".


This makes perfect sense because all of my rocket building has usually gone on during the winter when the humidity was relatively low.Subsequently I've never had any problems with Krylon,either.Also,I too like it a bunch but it hasn't been diggin' me at all this summer.This is the first summer that I have had this much time to build.