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Kevin K
Bubbles in Finish

I resurfaced a bar with maple luan. After staining the surface I cleaned with tack cloth and applied spar varnish. The first coat had a lot of little "bumps" so I sanded and applied a second coat. Still lots of little bumps. Third coat and same result. How can I get rid of the bumps in the finish? At this pace it will have 10 coats of spar varnish. Any help out there?:confused::eek:

A. Spruce
Re: Bubbles in Finish

What is the brand of spar varnish and how is it being applied?

It's been a while since I've applied this particular material, but I believe that it needs to be brushed with a natural bristled brush suited to this type of finish, a regular paint brush isn't going to cut it, neither will a sponge brush.

I also believe you need to use slow, careful strokes and as few strokes as possible to keep from whipping air into the finish as it's being applied, hence the lots of little bubbles.

Kevin K
Re: Bubbles in Finish

Cabot is the brand. I used a really expensive china bristle brush. I'm kind of thinking that despite the tack cloth I must have varnished over some particles and may have to sand it back down and start over.

A. Spruce
Re: Bubbles in Finish

The thing is with particles though, they may create bumps the first time through, but once you have sanded and tack clothed it down again, those initial particles should be completely gone. For you to be at the 3rd, 4th, or more coat and still have the same severity of bubble is an indicator of bad product or improper application technique/equipment.

Hopefully one of our resident experts will step in soon and offer their opinion.

Kevin K
Re: Bubbles in Finish

I suspect defective product. I was very careful to stir and not shake the can. The brush is top shelf. It could also be a lousy application technique on my part too. I'll go through it again. Would you recommend hand sanding or random orbital?

A. Spruce
Re: Bubbles in Finish

Hand sanding is best, since you're only trying to smooth the surface, not take the finish off.

ordjen
Re: Bubbles in Finish

I would have to agree with Spruce's advice on not overbrushing varnish. The more you stroke, the more the likelyhood of getting bubbles. A natural bristle brush is preferred. I liked to use oxhair brushes rather than china bristle.

I am curious as to why you chose a spar varnish rather than a urethane? Urethanes are the best for protecting against water and alcohol, both prevalent on bar tops.

Spar varnishes have a more flexible film than urethanes. This is a highly desireable trait when varnishing exterior panel doors which swell and shrink with the changing of the seasons. Indeed, the name "spar" comes from the marine world, a spar being a part of a wooden sailing ship.

I've done many wooden garage doors over the years. The manufacturer would have a sticker on the door advising the use of a spar varnish, both front and rear. The same sticker said the use of a urethane on the door would void the warrantee. Urethanes are very hard and brittle. When the garage door goes up and down, the panels move and a small crack in the urethane results. Water enters and the door is ultimately doomed.

Old fashioned "real" spar varnishes were made from pine resins. They never felt completely dry. When you passed your hand over the surface, it felt a little gummy. There are now synthetic varnishes which are designed to mimic ther spar varnishes flexibility.

Anyway, back to your bar top: I would try to wet sand out the surface using very fine sandpaper - 1000 grit or finer. You can even use rubbing compound to give it a mirror like finish.

If you have spraying equipment, you would probably would have avoided the entire bubble issue. Spray varnish in a can can also give a very good finish. Minwax makes an excellent urethane in a spray can.

A. Spruce
Re: Bubbles in Finish
ordjen wrote:

Minwax makes an excellent urethane in a spray can.

I agree with everything you said except this one point. Minwax makes great stains, but their top coats are utter garbage! If the OP thinks he's got bubble problems now, wait until he cracks a can of Minwax polyurethane! :eek::eek::eek:

HoustonRemodeler
Re: Bubbles in Finish

If you want a great spray on, use Helmsman which I find most excellent. Available at Home Burrito

ordjen
Re: Bubbles in Finish

Spruce,

I have never used the brushing version of Minwax Urethane, but I have used the spray cans often and have had nothing but good results. I built an oak computer desk and used the Minwax spray cans to give a factory like finish. It has held up for several years of me sitting at it.

A. Spruce
Re: Bubbles in Finish

Spray versions might be a different story, the brush applied stuff isn't worth the can it contained within.

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