Some suggestions:

If oil-based poly doesn't cause the vinyl to separate from the MDF (it shouldn't, but...), wash it with a degreaser and THOROUGHLY rinse and dry it. Apply three coats of poly, sanding between coats. You could also choose a wipe-on poly. It's thinner and dries to recoat way faster. You're doing speakers, not a table top, so you don't need the extra body of regular poly.

You can use semi- or full gloss. After the final coat is thoroughly dry, apply a real furniture polish (like Briwax, not bowling alley wax) and rub out any nibs with 0000 steel wool or the GRAY colored plastic equivalent. Buff it within an inch of its life, or your until arm falls off and there you go. (Seriously, a folded up cotton rag under a pad or circular sander works great and fast.)

Or...

If the ambering that will happen with the oil is not to your liking (it should make the plastic look realer, actually), then you can use a water-borne or water-based poly. You NEED to do a bottom test, because, though it dries water white (clear), it can impart a really unpleasant bluishiness to some wood colors.

A great wipe-on acrylic poly is Rockler Woodworking's "Wundercoat." I once used it on mission-stained oak and it did NOT leave a blue cast. Way, way fast and easy and not smelly, and clean-up at the sink w/soap. Nicer.

Do NOT use minwax acrylic products. They suck. Oil's fine. All really decent (still not as durable, ever) acrylic finishes cost over $100 Ga. If you insist, start with Campbell Finishes or General Finishes. Problem with all of them, is that to sand the applicator marks out, you have to sand off most of the coat you just put on. Wipe-on is formulated NOT to do that.

Then there's the chicken's way out of everything, that I call "spraying." The most beautiful pieces of art furniture you will ever see do not employ sprayed finishes.

If you ever need to repeat any of this, you can tell 'em an old fart who does everything by-the-(old) book told you.

I DO own a 4-stage HVLP system, and it was mfgd. in Canada, so don't even go there.


Last edited by BobKay; 03/22/16 08:16 PM.
Always call the place you live a house. When you're old, everyone else will call it a home.