[BradleyB]

I'm really enjoying this forum. I think it's success is a direct result of the generosity and good humour of the contributors so, thanks to all.

Here's my question - Can I get away with a water based primer on MDF before an opaque paint top coat? I know mdf doesn't like water very much and it will make it blister and swell. I've heard I should use a shellac based primer - VERY stinky and I don't want to use it indoors as, since its winter, I'll be doing it in my kitchen. Even an oil based primer would be better than the shellac one.


Any advice?

 

[BradleyB]

ooops, I've found the answer to my question. I'll post it here in case anyone else is interested. Looks like a nice finish is less important than sealing in the formaldehyde off-gases! Man, the MDF is nasty stuff.

This is a quote from a FWW article by Jim Haydon:

The level of formaldehyde in untreated MDF may remain above ambient levels for several years. High-pressure laminates offer almost total sealing, matching factory applied thin and thick vinyls. After that comes alkyd oil primer and oil enamel paint combined, two coats of polyurethane, and latex-ammonia combined with two coats of latex wall paint. (The latex-ammonia types will raise the grain.) Ironically, the effective alkyd oil finishes contain formaldehyde, but it normally off-gases in two weeks. Finishes that are less effective sealers include: oil base or lacquer sealer plus a top coat of varnish or lacquer; two coats of lacquer or oil primer; lacquer sanding sealer plus one or two coats clear lacquer; quickdrying lacquer sanding sealers; and shellac or varnish applied without a sealer. Despite their other merits, finishes that will not effectively seal in formaldehyde in MDF include: two coats of regular latex paint, penetrating oil sealer, stains, waxes or linseed oil