Power Buffing Conversion Varnish Finishes

A tiny spot repair turns into a blending hassle: how to buff a not-quite-glossy sheen into a conversion varnish coating that is at its mil-thickness limit. February 12, 2007

Has anyone had success power buffing conversion varnish (Sherwin Williams)? This is a large desk with a couple small blemishes that are sticking out. I have carved and filled and it's leaving an irregular spot which needs to be blended. It makes me want to sand it, but that would be disastrous unless I can buff the whole top. The SW people say they have heard it can be done but do not know the method. I am at the limit of film thickness with this top and don't dare apply one more coat. That's my reason for wanting to try this buffing. I know auto finishes are harder than CV, so why wouldn't CV buff? I need a medium rub gloss.

Forum Responses
(Finishing Forum)
From contributor D:
Yes, it's possible. I've done it several times. Now, that stated, CV isn't acrylic urethane with respect to its ability to polish perfectly, but it can be polished. Use a twisted wool pad to start and Menzerna's 2L paste. Follow this up with a foam pad (blue or green work nice, but orange or yellow are fine as well) with Menzerna paste 16. You can get this stuff from Jeff Jewitt and several other sources.

From contributor D:
I should mention that this will give you a gloss finish. The best way to dull it down is to get to full gloss and then go over that with an Abralon P2000 grit pad used wet or 3M's Trizact used wet - both of these are used on a random orbit sander. This is the only method that I've had any success with when it comes to dulling a finish. The old "use 0000 steel wool" line is bull, as you can always see the scratch pattern.

The absolute best way is quite unusual. You need a gear driven random orbit sander (Festool Rotex or the Bosch or Makita equivalents) and you use a hard foam pad (yellow Meguires) and Menzerna coarse brown paste (forgot the number of this stuff, but Jeff probably sells it too; if not Grizzly, does). This leaves a nice satin sheen and is fairly goof-proof, which most other methods aren't.

The reason you need the specialized sander/polisher is if you use a normal rotary polisher, you'll get swirl marks. The orbital design of the Rotex cancels these out. It's very easy to polish something to full gloss and very hard to polish to anything less.

From contributor R:

That desk sure is kicking your but. So, you finally got rid of the bug skeleton and now you're faced with the shadow lines left from the fill-in. Any kind of buffing or polishing or tinkering with the finish will almost for sure leave its mark. Why don't you give this top a real good sanding and spray on another topcoat? Less work, and you could be sure of the sheen matching the rest of the desk.

From the original questioner:
Thanks. I will have to think this over. The detailed method is very much appreciated. She does want this fairly glossy, however too glossy might not look as good. This is an open pore wood, Lyptus, and I did not fill the pores. I did try hard sanding it and re-spraying the smaller section. Guess what? When you sand down an open pore finish, you level it... The pores filled in. Only problem is some are deeper than others to begin with, and the shallow ones filled in completely, leaving smooth spaces interrupted by areas of grainy pores. Not pretty. So I had to strip the small section. I finally got the two halves looking nice, even and a medium rub effect. That's SW for "semi-gloss."

The two small spots I worked on with a razor today and they are fairly level and not looking too bad. I was hoping a polishing step would blend them in more. The overall look is nice, but the combination of the black dye stain under all that CV is giving a milky look to the film. Would the effort of polishing mask the milkiness, or highlight it and make it worse? I'm almost ready to do something I never do... put some beeswax furniture polish on it and forget it. I know that's a copout, but for all my effort, I'm not completely happy with the results.

From contributor M:
Black is the worst for rubbing out. All of the scratches will show. I like the Abralon pads but I doubt it would be okay in your situation.