Blown the finish...not sure what to do next

[Mark]

Hey Guys, I'm up the creek without the proverbial paddle. I built a dinning table with bubinga top. I don't have much experience with finishing bubinga and kinda went through my normal MO for table tops. 3 coats of poly and then wait 2 weeks or so and rub it out. But the grain telegraph bugged me and rather than just let things lie and attempted to level the surface with 320/400 grit. It really made a mess. The poly was thick enough to allow some leveling and remove some of the grain telegraph. Of course at this point I'm thinking I should have filled the grain...too late for that. So after much sanding I kinda gave up and decided to live with the grain. Problem is I couldn't get up all the white residue from sanding, now wedged in the pores. But when I wet it with spirts it disappeared giving me the impression I might be alright. Now after shooting a coat of poly there still are telltale signs of the white lines in the pores from the sanding (not much but they are there)...and it's sealed in. What should I do. I'm thinking chemically strip the whole top and restart...argh. Is that even the right thing to do? Any suggestions? Mark

[David Nebenzahl]

On 6/13/2009 5:30 PM Mark spake thus:

If the white is truly "sealed in", then there's nothing to do, I guess, but strip it off. Ugh. You have my sympathy.

By the way, why do you use polyurethane? I hate the stuff myself, and only use what I consider to be "real" varnish, i.e., regular old oil-based varnish, aka alkyd varnish (goes by many names, but is basically the same stuff)? The reason I ask is that I've never had problems like you describe with this material. If you sand and recoat, any residue gets pretty much redissolved. (Maybe not quite to the extent that lacquer or shellac would, since the solvent redissolves the finish in those materials, but better than the plastic stuff.) Plus, the varnish lays down really smoothly and the last coat usually requires no rubbing out.

Just my $0.05.

[Bob S.]

Mark,

Did you change any wiring on the switch?

[Bob S.]

Opppss... wrong post..... long day.

[Norm Dresner]

I don't quite understand what you mean by "telegraph". I've used poly-based varnish on a 4"x36" tie rack with absolutely no problems on the finish. For other things made from the same piece of lumber I've used oils like Pure Tung Oil with great success.

Norm

[Sonny]

What do you mean by "not much, but they are there". Do you mean only a few spots (3, 4, 5) are like this or do you mean the affected spots are all over the surface, but each defect is much less pronounced? I'm thinking the latter.

Rather than stripping the whole, I would first try/test rubbing out those spots/lines with lacquer thinner, to see if that would remove the spots/lines. If you used water based poly, I'm not sure how effective the lacquer thinner would be. Test: Wet, well, a spot with thinner and rub fairly vigorously. This may leave a "dent" in the finish at this test spot. Also, rubbing with lacquer thinner may/will become gummy, as the thinner dries during rubbing. Work fast. If the lacquer thinner does remove the spots/lines, then after removing all, lightly sand the whole and clean the dust off (with dry cloth, air, other), then quick-wipe with lacquer thinner (rather than mineral spirits) and apply another top coat.

If the lacquer thinner procedure, above, doesn't help, then stripping would likely be the only alternative. After stripping, your stripper may require cleanup with mineral spirits. After cleanup, light sanding and removing dust.... with dry cloth, air, other ..... wipe down, well, with lacquer thinner, before finish coating, again.

If you end up stripping it, using a scraper to remove the gunk, apply more stripper, after the initial removal, and scrub with a stiff brush to get into the pores. Scraping, alone, will not (may not) get the initial gunk from the pores. A hard bristle tooth brush works well. Subsequent stripper cleanup with mineral spirits: Again, use the stiff brush for the pores.

Sonny

[J. Clarke]

I think he's looking for a glassy-smooth surface.

[Mark]

Hey Guys, thanks for the help. I thought I'd gave all the details, but always manage to forget a couple of points. I used oil based poly. I chose poly because it's a dinning table and expect to get fair share of abuse. Admittedly I usually use poly on projects and have generally had good luck with it. The few varnish projects I've done have come out too, but don't seem as durable. Oil (tung or modified tung) projects for me have not had great results. Looks great immediately after finishing but seems to be a dust magnet...they never seem to really totally dry. Shelac and lacquer are out for a dining table as they have so little resistance to water.

So thanks for the tips on the stripping. Never thought about having to "scrub" out the gunk from the pores. Most likely will since that is the crux of the problem. Oh, and yes the white marks are throughout the whole top (not localized in one spot), but they are the size of a hair in width and range from a spec to 1/2" long, following the grain of the wood. Where the wood grain is more prevalent there are more. But since Bubinga is dark red they are easy to see if there is good light on it. If it was maple or oak they would most likely be invisible.

So since I posted it I've got the opinion of a couple friends first hand. My carpenter buddy says "Get over it. It looks fantastic as is". SWMBO says strip it. She says anybody else it would be fine, but it will bug you every time we sit down. I think the plan is going to be shoot one more coat as is, move it into the house and live with it a few months. Let the anguish blow over some. Strip it at the end of the summer and give it another try.

I'll be bugging the group again for tips on stripping. Mark

[David Nebenzahl]

On 6/14/2009 1:07 PM Mark spake thus:

There seems to be some confusion here over terminology. When you say "oil (tung or modified tung)", I assume you're talking about something other than varnish--namely some kind of oil finish, like tung or linseed oil. What I was suggesting was oil-based *varnish*, containing aklyd resins. This dries quickly (6-12 hours) and is definitely not a dust magnet when dry. As opposed to the oil finish that you wipe on, let absorb, wipe off, wipe more on, let absorb ... ad infinitum.

[Pat Barber]