Micro bubble formation using polywax sealer

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Makkum
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Micro bubble formation using polywax sealer

Postby Makkum » Mon Oct 12, 2020 7:52 pm

Good day. Forgive me if this is a trivial question that has been asked a million times before I am trying to refurbish a wooden table that I coated with a polywax sealer about 20 years ago. I sanded the table right down to bare wood with a belt sander and then a rotary sander, going from 100 grit, 150, 220 then 400. The surface looked beautiful. My wife wanted a gloss finish so I purchased a new tin of the same sealer but the gloss finish version, and applied 4 coats rubbing it down with steel wool in between coats. I cannot get rid of the small bubbles that form on the surface which dry to a very rough unpleasant finish. I then sanded the table down to get of all the bubble marks and tried again, this time leaving out the steel wool which I thought may be leaving fine particles behind. Again I went through the sequence of 150 to 400 and got a nice surface again. But the minute I apply the undiluted product with brush, I get millions of bubbles on the surface. I have refinished many pieces of furniture over the years using this technique (brush coated varnish) but this is the first time I have experienced this problem. Any advice would be greatly appreciated

AsonnyA
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Re: Micro bubble formation using polywax sealer

Postby AsonnyA » Tue Oct 13, 2020 8:08 am

Bob may have more suggestions, also.

I'm not familiar with that particular product. Spec sheet says it's solvent is aliphatic, mineral turpentine.

Spec sheet says drying time varies! What the hell good is that info.... "varies"? Does it dry to touch within 20-30 minutes or 2 hours. We need to know a more specific time for drying. That aspect of the spec sheet is severely lacking. Knowing the drying time may lend itself to resolving your problem.

Right off, there may be a couple of reasons why you're getting bubbles. I suppose the Polywax dries to touch within 20-30 minutes.... is this correct?

1) Use an appropriate quality brush. Some over-the-counter brushes are not appropriate for that type of finish.
2) Stir your finish, don't shake it.
3) Initially, dip your brush in solvent, to wet/dampen the bristles, before applying the finish.
4) Brush on the finish with slow strokes, not fast. Try to reduce the number of strokes it takes to spread the finish. The fewer strokes, the better.
5) When dipping your brush into the finish, load a generous amount of finish onto the brush, but don't overload the brush up to the heel/ferrule. You want enough finish, on the brush, to accommodate the slow-stroking and allow good coverage, without having to brush many strokes or to brush with fast strokes.

If the dry time for the Polywax is longer than 30 minutes, might the finish be wiped on, rather than brushed? Wiping might be a better application technique. You might try some wipe-on testing on some scrap wood or on the underside of the table, if the dry-to-touch time is longer than 30 minutes.

Sonny

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Bob Boardman
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Re: Micro bubble formation using polywax sealer

Postby Bob Boardman » Tue Oct 13, 2020 9:35 am

I think Sonny covered about everything that I would suggest, starting with brush issues, and then using as a wipe on. The only things I can think of that might be worth a try are (in no particular order):

1) If table surface is NOT veneer, turn table over, sand to get to 'new' wood and use this as your 'test' area. If things work here but not on the top, then go to my last sentence.
2) Apply a coat of product called Sealcoat. Apply, let dry, light sand with a 120 grit, remove dust and apply your finish
3) Dilute the finish and try applying multiple thin coats, allowing each coat to dry thoroughly
4) Depending on size of table, instead of wiping on, get a bottle sprayer and a couple spray tubes (at box store or hardware store - PreVal is one brand). When spraying don't go too heavy - try to mist on a coat and let it dry. LIGHT sand with a 400 grit, remove dust and apply next coat. Clean spray tube after each application.

Lastly, it might be that you have what's known as a silicone 'infection'. It usually shows up as large areas with no finish, but can also show as bubbles in finish. IDK for certain, but I don't think that silicone is the problem, Certain spray on "waxes" like Pledge, Behold, etc. get their shine from liquid silicone. Manufacturers use it because dust, dirt, etc. don't stick to it. But neither do finishes! If all of Sonny and my suggestions don't work, let us know
Bob "Boardman" Borders

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Re: Micro bubble formation using polywax sealer

Postby AsonnyA » Tue Oct 13, 2020 3:09 pm

Another thing I thought about....
I often use water based Varathane floor finish for *utility pieces, not fine furniture. I almost always get air bubbles you describe. I remedy the bubbles by applying a good coat of finish, then wipe my brush relatively dry with a paper towel, then slowly brush back (1 or 2 strokes) over the application. The dryer brush seems to pop the bubbles while the finish is still wet. I immediately repeat this process, if need be, and almost all the bubbles are removed; very little, if any, bubbles remain. The first dry-brushing collects some of the bubbles on the bristles, hence, wiping the brush again, to remove those bubbles, then swiping a few more gentle brush strokes.

I like Bob's spray bottle recommendation, also. I always spray finishes when convenient. I've never used a manual spray bottle, though, so I need to try it. Any miscues should be able to be cleaned up, "fixed", with a small brush and gentle brushing of drips and such, similar to brushing small drips when spraying with air guns or aerosol/rattle cans. If you opt for a manual spray bottle, do some practice sprayings if you're not familiar with them.

*I recall having this bubble issue when finishing this rocker, made from salvaged cypress lumber. The whole of the wood surfaces were not completely smooth (I like the rustic look and "texture" of unrefined wood), so those irregular wood surfaces contributed to creating the bubbles. The dry brush, paper towel technique resolved the problem, as with other pieces I've done.
https://www.flickr.com/photos/43836144@ ... otostream/
https://www.flickr.com/photos/43836144@ ... otostream/
https://www.flickr.com/photos/43836144@ ... otostream/

Sonny


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