Conversion Varnish as Primer Under Paint
From Paul Snyder, forum technical advisor:
When I do primer only jobs, I stopped using a catalyzed primer because of a complaint from an on-site painter that the paint wouldn't stick. I don't know what kind of paint they were using, but to avoid the problem, I switched to a single coat of pigmented shellac for that work.
Acrylics are known for their adhesion properties, so you may be okay as long as your paint is 100% acrylic and you scuff the primer before painting. Get a sample door from your supplier and paint it. Let it cure for a week or more and then do an adhesion test.
Testing is always a good idea. I would not recommend the system for exterior application. I have found CV primers and latex paints to be a good combination. Sand the primer with 180 grit or 220 grit sterated paper, tack off the dust and paint away. The latex has great surface adhesion to a clean, coarse film. You will get no chemical adhesion.
Don't depend on the sanding/scuffing to give you a better bond. If the sandpaper is too coarse, it will leave telescoping grooves; if it's too fine, it will do nothing. Sanding is basically done to remove any gloss, which has a slick surface that prevents adhesion.
I have heard (though not seen) acid catalysts causing latex to turn green. I think the pigmented shellac is a great choice, since it's basically inert after the solvents have evaporated, much like plain old lacquer.
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