I have two interior doors which were once varnished. I've sanded them, and applied two coats of white undercoat on one door . Staining, traces of the varnish are discolouring the paint. What should I do?
Apply white gloss top coat and hope the varnish doesn't come through? Or use some sort of primer, then undercoat and then gloss top coat? Or something else?
And what about the door that I haven't yet touched? They are both too fiddly and ornate to sand further.
It sounds like something in, or on the varnish (if that's what it really is) is being softened by the solvents in an oil based undercoat, and is 'bleeding' through.
Two courses of action - Give your undercoat a few days to fully harden, a light rub down, then a coat of a sealer such as Zinsser BIN, then carry on with undercoat, and gloss. Or, a coat of Zinsser Bullseye 123, and follow on with a water based gloss system. I wonder what the existing finish really is. Some sort of wood finish or polish, conventional varnish won't cause the problem you're having.
Proptech, thanks for your reply. I joined especially to ask this question. The undercoat is Dulux solvent-based. I can't recall seeing Zinsser products in the local (UK) DIY shop. I saw something that is recommended for painting over nicotine stains and wax crayon. Is that the same sort of thing? It doesn't say if it is suitable for on wood, just walls and ceilings. The website text describes it as:
Interior Stain Cover is specially formulated to cover and lock in unsightly stains caused by nicotine, smoke, marker pen, wax crayon and graffiti. Ideal for interior walls and ceilings, it provides a good covering of the substrate and prevents stains bleeding through.
For use on interior mineral surfaces, wood and some plastics Covers and locks in stains such as marker pen and nicotine Tough solvent-based formulation
If that is OK, do I then just do topcoat or do I need more primer or undercoat?
Also, what about the door that I haven't yet touched?
You won't get Zinsser products in a DIY store. You need a proper decorators merchants. Can I suggest you have a look on the Zinsser web site. These are trade quality products that can be trusted, unlike some from the likes of B&Q.
On the untouched doors, I would be inclined to go with a coat of the Bullseye on a small area, and experiment a little. The problem being that we don't know what the existing 'varnish' really is.
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