bubbles

[NOT Firewood]

I am getting bubbles in the finish of my varnish. I varnished at 6pm yesterday and check it this A.M and dry to the touch I thought it was all good. Then when I came home after work 11 hours later and checked now I have bubbles. Help.

[Captain Nemo]

-OH BOY- Another varnish thread . These tend to be long and interesting.
Let's start out w/ the basics, don't shake the varnish. Many jobs have been ruined by shaken varnish syndrome.
Another thing is to not wipe off the brush on the edge of the can. That causes air bubbles to run down the inside of the can into the varnish, hence into the finish. Just lightly tap it off on the side of the can.
Just a couple of things I'll leave you with and let others explain the black art of varnishing.

[ssnider]

I am doing some varnish work myself and got bubbles as well. I think mine might be coming from my varnish bucket.



Question of my own:

- I have read it is best to varnish in the middle of the day when moisture in the air is at its lowest point. How much does this really matter? I have also read to wash down the varnish room floor with a mop before applying varnish, seems as though this would increase the moisture in the air.

[mattwells]

Are you positive they're bubbles and not dust? Dust specks make craters that look like bubbles.

Can you post pics?

[jwoldeboat]

are you brushing ?? and if so It is important that you use a very good varnish brush, or are you rolling and tiping with a foam brush? I have been varnishing boats for many years with a brush and swore I would never give in to the roll and tip method but out of curiosity I tried it,results ,first time hated it ,second time not as bad and after several more tries and finding the right type of roller I am coverted . I wet the shop floor down and try to varnish @65 deg and 50-55 % humidity Found this works well for the brand of varnish that I use,different brands may require totally different temps and humidity levels. Bottom line that I have found is that varnishing requires lots of patience,experimenting and lots and lots of practice

[JimF]

It is not unusual to have bubbles as you brush on varnish, particularly on a deck. The bubbles should disappear after a few minutes as the varnish levels out. If they do not go away, they are not bubbles but they are dirt. Dirt can be on the surface, in the brush or in the varnish or in the air and then it lands on the boat. Much has been said in books and on this site. Clean, clean, clean.! That being said, the point of a boat requiring 10 coats is that you get to practice on the first nine! Those little specks will sand out and then you get to do it again. Most boats get several "final coats".

[NOT Firewood]

What gets me is that it was dry to the touch in the AM and looking good. I came back 12 hours later and I then had bubbles that you can pop. I will have to wait for warmer weather, I guess. The shop is heated but only up to 60 degrees is all my heater can do.

[JimF]

It sounds like the surface dried too quickly and as the deeper part dried, the gasses pushed through and made the bubbles. This may be caused by cold temperatures or too thick an application? There is probably a phone number for technical assistance from the manufacturer on the can. You might give them a call since the problem is not dirt.

[Jim Godlewski]

This sounds very familiar. Oh... That was my varnish job. What kind of varnish are you using? Roll and tip I’m guessing. That’s what we did and got bubbles too. We are using Interlux Schooner 96. We 220’ed the bubbles down and reapplied. They were less and less on each coat. Were not done yet bit the bubbles are less of an issue.

[RRGadow]

It also happens sometimes if the grain hasn't been filled correctly...air gets trapped in the pores and slowly makes its way to the surface.

[John DeVries]

Varnishing is possible at 60 degrees. What type of heat is being used - forced air, infrared, in-floor?

[57 chris]

I believe Jim Freschette is on the right track. If these bubbles are forming after a period of time the surface is drying too quickly not allowing the material underneath to "gas-out". I also have had this problem when using artificial heat. There are many good suggestions in this post with regards to clean, temp and humidity and it is very true that different products will require different heat and humidity conditions. There's no sure-fire answer to this anomily but it's true that "practice makes perfect" (or close)!

Craig

[chriscraft55]

The artificial heat may be the culprit here. I just did my 16th coat of Captains (sprayed on) with no bubbles at all. I heated my garage up to aprox. 55 degrees, turned off the heat (electric radiant heat) and left it that way over night each time I applied a new coat. The varnish should still dry if the temp stays around 50 degrees. Remember not to shake the varnish either, that tends to create bubbles.

[John DeVries]

My reason for asking about the heat source was that I was thinking about the effect of an infrared heat source on drying varnish. Since infrared heats objects (a boat hull) and not the air around it,there might be some sort of distruption of the normal drying process - causing the formation of bubbles at such a late time in the process. Anybody out there have any experience with this type of heat?

I don't get too concerned about bubbles in varnish cans, or anywhere else. They all flow out in the application. My way of varnishing hullsides is to roll the varnish on and then tip it off. Taking about 4 ft. of hull at a time and rolling over the surface several times, I look for a uniform bubble size and quantity, which I feel helps achieve a consistant application thickness. All of those bubbles are also a handy guide for the tip off phase. I've done this on several boats now, and sags and "holidays" are almost a thing of the past.

[Al Benton]

When I first read this I was skeptical. Just how is it possible for bubbles to appear in varnish long after it already feels dry to the touch. It doesn't sound likely at all. How would gas seep through the surface that feels dry? I'm not sure how but if it happened, then it happened.

It would probably be sheer luck to set up a test model that would result in the same thing happening again. Varnish has solvents that need to evaporate as it cures. If the wood surface was cold when varnish was applied it would drastically slow down its curing time. If artificial heat was added to warm the work space shortly before applying varnish it's possible that a thin film of varnish would begin to cure on the surface. As the varnish begins to warm, solvents would begin to evaporate under the film. It may be that this caused gasses to break through the thin film that brought along uncured varnish that formed the bubbles.

It's probably a wild theory but...

Al

[NOT Firewood]

Thanks for all your answers and suggestion. have a 220 electric heater in the shop and maybe the parts and the varnish in the shop were still cold even that the room was warm.Or too thick. Anyway I am going to wait for another week or two before I try this again. As I have at least another 4 week before the ice is off the lakes, up here in North. I let you all know the results on the next coat.

[mstover]

Gentlemen: I had problems with bubbles when I applied varnish with a brush... I switched to a roller and tip method and haven't had any bubbles using this method... However !!! I am having problems with the vawrnish "marbleing" ... not flowing out and making a nice flat surface. All pores are filled... have 5 coats on now. Using Interlux Schooner Gold varnish, and pre-wiping with Interlux 333, and thinning also on some flat surfaces with the 333. The temp. is above 65.... any suggestions?

Thanks M.Stover`

[JimF]

While my experience with varnish is only with brushing, not roll and tip, my best advice would be to dump the Schooner Gold 500 and get the old stand-by Schooner 96. I just went through about 6-8 quarts of the gold because they said the 96 was discontinued. I found it to be too thick and even with temperatures at 80 it still required thinning and would not level out. The 96 is available again at Jamestown and probably other suppliers. I used it today and varnishing was again a satisfying experience.

[Don Vogt]

Those interested in doing their own varnishing might want to look at the current issue of Wooden Boat magazine. There is a nice article on how the Sierra Boat Co. varnishes runabouts.

[NOT Firewood]

Again guys thanks for your help. I did another coat and much better. It had to be just to cold. I have to go the ice is off now and I have another 2 weeks of work to do.

[mstover]

Gentlemen: After putting on 4 coats of varnish using Schooner Gold with horible results (mainly it did not spread out even with thinning) I changed to the regular Schooner Varnish, and I must say, I was astounded. It went on smoothly, with no thinning, and it looks like glass. I rolled it on and tipped with foam brush. I'm now looking forward to finishing the varnish job instead of dreading it. The interlux web site has customer comments on the "Schooner Gold", and no one has anything good to say about it.
Marty Stover, 1957 ... 17' runabout.

[Al Benton]

Marty,

The Gold is a polyuerthane-modified alkid and the Schooner is straight tung oil which flows and levels much nicer. I've found the Schooner easier to get good results with.

Al

[NSJA]

Don,

Is that the April issue of Wooden Boat?

[Don Vogt]

Its the May/June issue that just recently came out. BTW, how are you coming on your boat?

[NSJA]

Don,

Thanks. The May/June issue is not out in CA as far as I can tell; I will keep looking. The boat is doing great and how is Jenny II?

Neil

[Don Vogt]

Thanks, Neil, I am about to get Jennifer II out of storage. I think all of the "bugs" have been gotten out so looking forward to a fun summer of use!