Hi I want to paint a door trim that has a few coats of oil based clear polyure thane. It is pine and therefore lots of knots. On a similar project I appli ed 2 coats of Bin Shellac Primer Sealer and then applied 2 coats of latex w hite paint.... however, the knots still bled after a few months. From what I've read, Bin it is the "best" primer for knots. Should I apply an oil bas ed primer before Bin? Anyone with suggestions? A
I'm surprised that knots are coming through polyurethane, but if they are there's not a lot you can do. Bin and Kilz are both pretty good for stains. They work because the top coat doesn't redissolve them, so the stain is stopped at the level of the sealer. But knotholes will usually come through eventually if the wood is reasonably fresh. The only good solution is clear wood. Knotty pine is for "country look" decorating.
"It is pine and therefore lots of knots."
Unless knots were intended for "atmosphere" it's just a case of someone cutting corners. Decent trim should be at least clear pine. Poplar is better. Knots don't belong in painted wood in the first place. And these days poplar is actually competitively priced with pine. It's usually cheaper than clear pine, it's less "dentable", and it takes paint better. The grain is very fine so there's no problem with grain lines showing through the paint, as often happens with pine.
If it were me I'd remove the trim and use poplar. If you keep the trim there's another issue: Polyurethane is basically a sheet of plastic. If you paint Bin and then latex paint it won't bond well. It may peel. It will probably scrape off easily. It may also shrink away, leaving splits where the poly shows through. (Ever notice how poly over old poly peels like a sunburn? The may be both poly, but the old layer is cured to a sheet of plastic, so the new layer doesn't properly bond.)
Whenever I need to paint or poly over cured poly I first wipe it with sanding liquid. I mean the fumey stuff, not newer versions. The sanding liquid softens the surface, making it as though you're painting over fresh poly, so that a new layer can bond to it. (It's ssomething like dilute stripper.) I would then prime it with something oil-base -- Kilz would be OK. Oil base underbody would be much better. (Benj. Moore makes one.) After that you'll have a surface that acrylic paint can stick to.
Bin is pretty good for spot priming but it is a sealer. It's not designed as an underbody or primer for large areas.
Thanks Mayayana, I agree the best thing may be to replace the trim but I was using it as "pr actice" since I also have a knotty pine ceiling that I also want to paint w hite. This wood is about 25 years old and I would not consider it fresh at this point. I don't want the expense and trouble of replacing a large ceili ng but at the same time I hesitate to paint it if all the knots will eventu ally bleed through. That would look unsightly! I might have to live with th e old wood ceiling even though a nice white one would brightened up the roo m.
Or you could put 3/8" drywall right over the pine, if you're ambitious. (Personally I try to avoid that. I always seem to end up with something out of joint in my back when I do drywall ceilings. :)
Is the room tall enough for a drop ceiling with white tiles?
Paul
Not an option!!
Yes, but I dislike tile.
If it already has 2 coats of oil based polyurethane, I can't imagine that the knots would bleed through. And, I wouldn't think that you would need any type of additional sealer or stain killer, and you should be able to just paint the trim with any paint with no problem.
When you say "on a similar project" do you mean that the original wood already had 2 coats of oil based polyurethane, and then you applied 2 coats of BIN shellac primer sealer, and then 2 coats of latex white paint (4 coats altogether), and the knots still bled through? If so, I just can't imagine how that could be possible.
Bin and Zinsser are the famous primers, but they make numerous types. They, as well as most major paint companies, make STAIN BLOCKING primers. Look for a primer that includes stain blocking on the label; oil or latex doesn't matter much as long as the label addresses your conditions. Follow all instructions on your primer and paint for drying time, recoating, etc. Be sure it is clean (door trim usually has lots of greasy fingerprints) and sanded and free of dust.
Yes, they still bled after a couple of months. :(
yurethane. It is pine and therefore lots of knots. On a similar project I a pplied 2 coats of Bin Shellac Primer Sealer and then applied 2 coats of lat ex white paint.... however, the knots still bled after a few months. From w hat I've read, Bin it is the "best" primer for knots. Should I apply an oil based primer before Bin? Anyone with suggestions?
I did not sand... maybe that is he key. I user "Primer Sealer Satin Killer" .
Sanding only matters for adhesion.
I can't imagine how they still bled through unless maybe the polyurethane was water-based and not oil-based polyurethane. But, you said it was oil-based polyurethane (2 coats), plus two coats of shellac (Zinsser BIN shellac-based primer sealer), plus 2 coats of latex paint on top of that.
I believe you, of course, since you are there and I am not, but I just can't imagine how the bleed-through could be possible under those circumstances.
TomR, Because the poly is old, I assumed it was oil based but I could be wrong. Nevertheless, wouldn't you think 2 coats of Bin & 2 of white latex would do the job?
Yes, I would also assume that even just 2 coats of Shellac-based BIN would have done the job. But, maybe that's not the case sometimes.
And, I would have thought that even just two coats of oil-based poly alone would have done the job. But, as you said, maybe it was water-based poly rather than oil-based poly.
It is all still a mystery to me (and you).
If it doesn't you have other problems. I would have sanded the door and primed it with either Zinzer BIN or Original Kilz (oil based)tinted to final colour if not painting white. My preference would lean towards the Kilz, personally.
| Because the poly is old, I assumed it was oil based | but I could be wrong.
Some old woodwork is coated with shellac. It usually looks slightly reddish, and breaks down a bit over time. The real test would be whether it's softened by denatured alcohol.
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