Painting issue

[Phisherman]

I have almost completed painting 400 feet of crown molding (before installing). I applied a shellac-based primer to bare pine, waited 1 week lightly sanded and dusted, applied a water-based semi-gloss enamel, waited one week, sanded lightly, dusted off, and applied a second coat of enamel. In three spots during the final painting the first coat sluffed off to the bare primer! I used a clean paint brush with nylon bristles. Any ideas what could cause this?

[slashdev]

Did the primer say it was OK for use under water-based finishes? I'd guess there was wax in the shellac. You can buy de-waxed shellac for use under water-based poly, though. Just not sure about your primer...

Good luck! /dev

[Morris Dovey]

| I have almost completed painting 400 feet of crown molding (before | installing). I applied a shellac-based primer to bare pine, | waited 1 week lightly sanded and dusted, applied a water-based | semi-gloss enamel, waited one week, sanded lightly, dusted off, and | applied a second coat of enamel. In three spots during the final | painting the first coat sluffed off to the bare primer! I used a | clean paint brush with nylon bristles. Any ideas what could cause | this?

Sounds like a PIA! If you're looking for guesses, mine would be: wax or oil contamination in the shellac, oil in the brush, or WD-40 sprayed in the shop sometime during the week the primer dried.

I'm not a painting guru, so these are truly guesses - and worth not more (likely less) than what you paid for 'em. :-)

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Robatoy]

Are the spots fingertip size? Have those fingertips been exposed to any type of caulking?

[CW]

Sounds like likely causes except for the WD-40. Unless sprayed on the work, that wouldn't make any difference.

[Morris Dovey]

I don't use all that much of the stuff, so I buy it in aerosol cans that come with a little plastic tube for the aiming-impaired. I've managed on a couple of occasions to shoot the darned stuff (accidentally) halfway across the shop and onto things that really didn't need it. If I can smell it, then I assume there might be some droplets floating about.

-- Morris Dovey DeSoto Solar DeSoto, Iowa USA

[Phisherman]

No. They are irregularly shaped, perhaps the size of the palm of a hand. I have not used any caulking, nor solvent in the shop in the past 4 weeks. My plan is to sand, re-prime (Zissler), then finish. It's no big deal, I just wondered what could be the cause.

[nailshooter41]

The "palm of the hand" is probably a good guess. Today's lubricants/solvents with all the goodies in them hang around on the hands sometimes for a while. And remember, it may not have actually been you. The guys that sent it out to you may have oiled or lubed something before handling your material. Once the propellants disappear from lube sprays they can be hard to detect. Since you used a solvent based primer, it is easy for the oils to migrate through the shellac/primer, and the longer it sits, the more will surface.

When I run into this, here's what I do: clean the spots with some kind of thinner (lacquer will chew through just about any lubes and a multitude of other stuff), sand lightly, and clean again. The apply your Zinsser.

Allow to dry completely (1/2 hour should be more then enough) and apply your paint as soon as possible.

I would think that would probably do it for you.

Robert

[Phisherman]

I sanded the areas today, down to the primer. (The primer won't sand off with 220 grit.) Then I applied the paint. Sadly, as the paint dried it turned into a rough texture and it looks like the paint won't stick to the primer. Like you said, I'm believing some kind of oil is coming up through the shellac-based primer. Just what is lacquer thinner? Do you think acetone will clean it? I could use a TSP solution (excellent at dissolving grease), but that means the wood may get water in it. The good news is that I can work on this problem in the shop and not the ceiling! And I'm lucky this problem is limited to only three areas. Good post, thanks Robert!

[Mike Marlow]

So - the primer is dry and showing no signs of softness, etc. In other words - good primer.

Not likely. If it were, there would be evidence in the primer itself. You're not seeing adhesion problems with the primer and the primer itself is cured, so it's not likely that you're bleeding anything through it. I'd be more concerned that the primer itself is leaching. If it were oil leaching up through I'd expect a reaction with the primer. I think I'd rough up the affected areas and re-prime.

Exactly that. Typically large concentrations of acetone and/or toluene with a few keytones and some other pretty nasty stuff. Disolves almost everything known to man... except silicone. Nothing seems to breakdown that stuff. Here's an MSDS on one lacquer thinner product...

Do you think acetone will clean it?

It will clean it, but it can also very quickly disolve it. A paint thinner (mineral spirits) might serve better, or denatured alcohol. If you use acetone, use it very sparingly and quickly. Don't saturate the primer.

If you've got a good primer coat and don't hose the TSP on, you should be ok.

My original thoughts when you posted this problem were that it sounded to me like you had a mixture problem and did not get your primer well mixed, resulting in those three problematic spots. I'm still thinking this may be the case, so I'd go with re-priming the affected areas and a small area surrounding them.

[nailshooter41]

It can be harder to detect in some cases than others. And you know now it is something on the wood. All you need now if proper prep and you are on your way.

We run this very problem from time to time when we repainting door frames (and sometimes the doors themselves) when home owners give the hinges a little spritz of some lubricant. It gets on the doors and on the frame, and even when we prep it and prime it, after it sits for a while until we get to painting that stuff sneaks back out.

Several years ago the combined brain trust on the job noticed this type of paint problem and we were able to figure out what was going on because we could see the pattern of bad adhesion exactly lining up with the hinges. A quick word with the client confirmed this as the problem.

I clean with lacquer thinner as it is extremely/immediately effective on most lubricants and it flashes off really quick so you can continue working in minutes. But it is dangerous, and the fumes will knock down a horse. Imagine your significant other's nail polish fumes times 100 and you have it.

Here's something to consider, and I am just putting this out there since it works for me. Our local paint rep for my favorite paint spends a lot of time defending his product, and the problems are almost always improper application. I had the same adhesion problem on a door, under a knob and it was a streak that went from knob to slab (exterior door). He said that the solvent based primers often picked up enough oil or silicone to contaminate the primer, making hard for the primer to seal completely but also for paint to stick to the contaminated primer. (I immediately saw in my mind's eye one of the guys brushing the primer on, effectively spreading around the contaminates with his brush). Our primer was hard, but the paint still pulled away in small streaks while it was drying.

So... since we had nothing to lose, we sanded off the paint/primer back to good areas. I cleaned it with lacquer thinner, and then we put on WATER based Kilz 2 as he suggested. Yup, water base. I was really reluctant as I had never used water based stain killer/primer on anything. And thankfully it worked fine. I guess the water didn't have the solvents to activate dissolve whatever it was on the door. Finshed out the door as usual, and something new learned.

This is our modified method when we have a few hundred feet of moldings to prime/install/paint: put it all out on the saw horses and shoot it all with water based Kilz with the airless. If you use the airless, you will not spread around contaminates (barbecue grease, taco grease drippings, pizza grease, fried chicken grease, from the delivery/yard guys, or oil from a careless spraying, etc.) that seem to wind up on your moldings and material from time to time. I don't like the water based stuff for actual stain blocking as much as the old solvent based, but it makes a good primer.

Do what Mike said; sand all of it off the affected areas. Clean with some kind of solvent, then prime (think about the water based stuff if you sand back and it still doesn't work) and paint.

Since you have 3 spots to experiment on and rework, just do one, and if your method works then take the time needed to do all three areas. Let us know how you are doing.

Robert

[Phisherman]

I solved this issue on the second try. Here's what I did. Using 120 grit sanded the areas down to the primer (wow--that Zissler shellac-based primer really sticks to bare pine!). I cleaned the areas with acetone. Sanded with 220 grit. Applied the shellac-based primer. Sanded with 220 grit. Applied two finish coats, sanding with

220 between coats. Looks great. Thanks for all the suggesti>I have almost completed painting 400 feet of crown molding (before

[nailshooter41]

Good for you! In the end, determination pays off.

Robert