Paint fail question?

[Ross]

Looks like contamination to me. What did you scrub with? I use a maroon scotch brite pad with dish soap and water, and scrub while I rinse, not just spray it off. You might have silicone contamination, which is VERY hard to eliminate. Also could be from the air hose, as was said previously. I agree with previous responses regards sandpaper, should be finer than 120, at least 220. The paint "bridges" over the coarse scratches. I think maroon scotch brites are about 320, that's why I like to wash with them. Not getting enough paint on is one thing, you can always change your spray technique, but contamination is the biggest problem here. Lacquer thinner will usually degrease well enough, but not if the problem is silicone. You said the rags were fresh out of the laundry- are they "shop towels"? Notorious for being contaminated, and you can't wash them enough to remove silicone. Also, wipe the air hose down with lacquer thinner. Painting outside? Lots of crap is on garage floors, brake fluid, antifreeze, etc. Outside, it's mostly just dirt, which is bad, but not a lot of CHEMICAL contamination at least. Let it dry, scrub it down REALLY GOOD again with a scotch brite, and try again.

[ol trunt]

You are spot on Bud. I didn't want to try to explain bridging as it is a sure fire way for a novice painter to really sc--w the pooch and end up with a stucco like result and runs that could be hung on a clothes hanger. It is a great technique and I've found it is best when doing a bridge job with a HVLP gun to cut the paint flow way down to avoid stucco and then do a cautious full flow finish coat. It is also a great way to hide hairline cracks in flexible bumper covers.

I'm sure I'm not a better painter than you but I have had an extra 30 years practice. Lots of hypotheses here from several non painters so it is fun to watch and see who's advice is followed. Nobody wants to be "teached" and I get that. I sure didn't learn to paint without my own failures.
Jack

[Ross]

I'm gonna agree with Budbrother. Yes, absolutely, "dissolve" the contamination, and wipe it off with a dry CLEAN rag. I've had some paint jobs (fortunately, only a couple) that got A TON of fisheyes in 'em. Had to be some silicone-ish stuff snuck in on something somehow. All you can do is do it over again.

[Skipoffools]

What was the weather like?

[PNW_Steve]

Weather has ranged from low 50's to low 70's with some wind.

I washed & scrubbed with Dawn dish soap then rinsed thoroughly. Then I wiped down with wax & grease remover. Then sanded. Washed with dawn again & thorough rinse. And finally a last wipe down with wax & grease remover.

I have sanded the bad areas down to metal, primed and painted. Fixed about 95% of the problem. Fortunately the few less perfect spots are under the solar panels.

I cleaned the sides using a similar process then primed and painted the sides and had no issues.

I don't have any idea what may have gotten on the roof before I bought the bus. Since I have owned it, there has not been any silicon within 10 feet of the bus.

It's all good now. The mystery contamination is gone.

[EastCoastCB]

the roof is a large target for contaminants!