Varnish help

[skipmac]

I managed to avoid varnish for forty years but now I have a couple of small projects that kind of need it. Read the books and threads and it's going pretty well. Have a good build, 8-10 coats but I'm having a problem getting that last, perfect coat on.

I'm using Schooner Varnish. If I use it straight it is too thick, is very hard to get even coverage, leaves brush marks and starts to cure quickly. However when I thin the varnish it makes bubbles; many, many very tiny bubbles. I am not shaking or agitating the varnish to mix in the thinner and the varnish in the cup is crystal clear.

The bubbles seem to form in the varnish after I brush it on. It doesn't look like they are coming from the brush but actually form in the varnish after a pass, like bubbles forming in carbonated water.

I am using Interlux 333 thinner but also tried mineral spirits with the same results. Have also varied the amount of thinner from just a few drops to 20-25%, also with the same results

I am sanding with 220 or finer between coats, wiping down first with dry cloth and finish with a clean tack cloth. I have also tried wiping with mineral spirits between coats, waiting a couple of hours to allow the MS to evaporate.

So what am I doing wrong? Any hints or fixes?

[Delancey]

I usually have the best luck achieving the candy coating by waiting til the spring when the Cottonwoods are blooming and then buffing with 3M Finese-it.

[Steve Bean]

I searched for "defects in varnish" and found bozzle.com which discusses various problems and their causes and cures.

[beneteau-500]

I recently varnished the rails on my canados m/b I used stoppanni what I found with using this particular varnish is 1/ I sanded timber back in stages from 120 grit to final sanding of 320 grit 2/ then washed timber down left for two days 3/ final sand was with 400 grit . 5/ temperature is critical I found between 15c and 25c the best . 6/ the first 2 coats I applied was diluted to by 75% ie 25% varnish 75% thinner and yes I got a few bubbles. But don't worry one thing I did learn was not go brush over the area you already covered . 7/ I sanded back between every second coat only with 440 grit 8/ the varnish/thinner ratio for next 4 coats was the same as the first two coats then reducing by 10% of thinners every two coats until achieving a ratio of 70% varnish 30% thinners
8/ note by the 5th coat air bubbles disappeared .

Note the above procedure was how I was shown last yr when I spent 3 days in the canados ship yard in Italy and now that I have done it I can say it works and looks fantastic ,

Don't rush take your time and it will work

[chris95040]

I wonder if it's bubbles or bits of dust.

It's so, so hard to avoid dust. Japan drier helps- curing it before too much dust can drift in.

Are you outside? Then it's just in the air, you should be under a tent.

Are you under a tent? Your nuts man, that things loaded in dust.

Several cleaning passes ( I use a bucket of water and a zillion blue paper towels. Fold a piece in 4, dunk it, wring it out, use a few sides of it, then drop it. Never put a dirty towel in the dunk bucket.) and then having a tack cloth (a purpose made, sticky cheeseclothy one) with you as you varnish helps.

Use the biggest brush you can, apply the stuff, then maybe one tipping pass (even, light, straight strokes along the last couple square ft you applied), then move on. It will never look better than it looks after getting it on and then giving it one tipping pass. The thinner flashes off quick once it's a thin film, so you really don't have any time to screw around over brushing.

Temperature is super critical too. Don't ever try to varnish a surface that's warm to the touch. The flow will be all wrong, the timing impossible, and maybe it'll even make bubbles. Must have shade!

Oh, and clean your brush, even a new one. Especially a new one. Flick it around in front of a light and you'll be surprised. It's like they manufacture those things under my bed.

[beneteau-500]

Oh one thing the guys in the ship yard did say I must do was to warm the varnish up in the tin in boiling water ,
and they say bubbles are caused mainly by two things not mixing the varnish&thinners properly and allowing it to stand for the bubbles to rise to top and moisture in the timber and only use tack clothe as well

[Cap Erict3]

I've read that stroking back and forth with the brush can get air in it. I just lay it on thick in as few strokes as possible and wipe off the excess.

I am lousy at bright work and painting. Get it all over me and my work area.


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Looking for another pretty place to work on the boat.

[minaret]

Originally Posted by beneteau-500

Oh one thing the guys in the ship yard did say I must do was to warm the varnish up in the tin in boiling water ,
and they say bubbles are caused mainly by two things not mixing the varnish&thinners properly and allowing it to stand for the bubbles to rise to top and moisture in the timber and only use tack clothe as well

This. Warm the varnish. All bubbles should come out when you pour it through a fine cone filter. No direct sunlight.

[skipmac]

Hi All,

Sorry I haven't replied to all the advice. It was one of those weeks. But I did take time to read the posts and thanks for the help. Hopefully I can get back to boat work this weekend and try out some of these ideas.

Warm the varnish will be the test for the next coat. Any suggestion on how warm? I guess not boiling hot but hot or just warm?

[skipmac]

Originally Posted by minaret

This. Warm the varnish. All bubbles should come out when you pour it through a fine cone filter. No direct sunlight.

Have been using filters, varnishing in the garage so no sunlight. I check the varnish carefully and it is completely bubble free before I start the application.

And as far as I can tell, I am not making bubbles with the brush but the bubbles look like they are forming in the varnish a couple of seconds after I brush it on.

[skipmac]

Originally Posted by Cap Erict3

I am lousy at bright work and painting. Get it all over me and my work area.


------------------------------
Looking for another pretty place to work on the boat.

Isn't that one of Murphy's Laws of boat work. Any paint, varnish, glue, caulk or similar substance will jump over to and stick to your fingers, clothes and everything else within a 5-6' radius except the part you're trying to work on.

[skipmac]

Originally Posted by beneteau-500

Oh one thing the guys in the ship yard did say I must do was to warm the varnish up in the tin in boiling water ,
and they say bubbles are caused mainly by two things not mixing the varnish&thinners properly and allowing it to stand for the bubbles to rise to top and moisture in the timber and only use tack clothe as well

Mixing might be a problem or at least part of it. I am being so careful to not agitate the varnish and thinner to avoid creating bubbles that I might not be mixing it well enough.

[skipmac]

Originally Posted by chris95040

I wonder if it's bubbles or bits of dust.

It's so, so hard to avoid dust. Japan drier helps- curing it before too much dust can drift in.

Are you outside? Then it's just in the air, you should be under a tent.

Are you under a tent? Your nuts man, that things loaded in dust.

Several cleaning passes ( I use a bucket of water and a zillion blue paper towels. Fold a piece in 4, dunk it, wring it out, use a few sides of it, then drop it. Never put a dirty towel in the dunk bucket.) and then having a tack cloth (a purpose made, sticky cheeseclothy one) with you as you varnish helps.

Use the biggest brush you can, apply the stuff, then maybe one tipping pass (even, light, straight strokes along the last couple square ft you applied), then move on. It will never look better than it looks after getting it on and then giving it one tipping pass. The thinner flashes off quick once it's a thin film, so you really don't have any time to screw around over brushing.

Temperature is super critical too. Don't ever try to varnish a surface that's warm to the touch. The flow will be all wrong, the timing impossible, and maybe it'll even make bubbles. Must have shade!

Oh, and clean your brush, even a new one. Especially a new one. Flick it around in front of a light and you'll be surprised. It's like they manufacture those things under my bed.

No not dust, although I've got some of that too. Even checked with a magnifier to see. And yes I wipe well, clean clothes and paper towels and finish with a tack cloth.

I am keeping the pieces inside so they aren't too warm. It's been 95+ almost every day in FL, except for the days when it's dumping rain so nothing outside.

[skipmac]

Originally Posted by Delancey

I usually have the best luck achieving the candy coating by waiting til the spring when the Cottonwoods are blooming and then buffing with 3M Finese-it.

No need to wait for spring. Have plenty of stuff falling out of the trees year round in FL.

[Beausoleil]

Originally Posted by skipmac

... It's been 95+ almost every day in FL, except for the days when it's dumping rain so nothing outside.

That's most probably the root of the problem - it's too hot. The top layer of the varnish is drying too quickly, and the volatiles in the underlying wet varnish have no place to go, ergo bubbles. Try applying a couple of coats very early in the morning. Of course, you'll have to do it when the temp is still above the dew point...