applying varnish

[coolair]

OK, i have been playing with some of the deck trim, mainly the vertical piece right by the engine box. I think its mahogany, but not sure. I sanded it down really good, and have wiped it down with denatured alcohol before i apply a coat, I am using captains choice, just what i garbed to try. But now that i have a few coats, i keep getting bubbles when it dried, what am i doing wrong? I am brushing it, not spraying.

[Buju]

Could be several things... Could you post a pic of the bubbles?

Did they appear in the first coat?

I wouldn't use denatured alcohol to clean mahogany to take an alkyd or polyurethane. Mineral spirits would be fine. The denatured most likely opened up the grain a bit, and sorta counteracted the fine grit sanding.
May have also had some trace moisture in the wood, which the d.alcohol displaced, and the moisture is trying to escape, thus the bubbles...

Could be cold ambient temps, counteracted by a warmer substrate surface temp...( cold outside, but the wood is/was in the direct sun when applying, or drying)

Who makes Captains Choice? You mean Petit 1015 Captains Varnish?

[CaptPatrick]

Matt,

You can usually expect some out gassing from bare wood when applying a finish. This can be minimized by making sure the wood is not warmer than the ambient temperature before applying the initial sealer coats. As wood cools it contracts and forces internal air out. Thinning the first couple of sealer coats also helps penetration and reduces bubbles.

After sanding the sealer coats, any raw wood that is exposed by sanding through will be prone to new bubbles in those areas. Until you have achieved a full seal, bubbles can re-occur.

Bubbles that occur after the wood is fully sealed are probably coming from improper technique. Some things to avoid are:

1) Never shake or aggressively stir the finish material.
2) Don't start with a dry brush. Pre-condition the brush with the appropriate thinner and remove the excess by stroking it out on a clean dry soft cloth.
3) Don't work directly out of the can. Strain the finish into another container.
4) Don't dip the brush more than half way up the bristles.
5) Don't drag the excess brush load on the edge of the container. Tap the brush on the edge of the container to remove excess load.
6) Don't overwork the finish. Varnishes skin over rather quickly and once laid and tipped any additional brush stroke will tend to lock in air and brush marks.
7) Don't apply a finish under direct sunlight if possible. Shade the area if necessary.

Things to do:

1) Lay the finish on with smooth even stroke, keeping the brush at about a 45º angle. Tip off the freshly laid material with a very light touch of the brush.
2) Use an appropriate brushing liquid added to the finish material.

What you are seeing as "bubbles" could also be dust that is being introduced into the finish during application. A dirty brush or dusty environment must be avoided at all cost...

Varnishing, especially with brush application, is an acquired skill and the initial learning curve can be dauntingly steep. Read up on the available info supplied by both the manufacturers and craftsmen using the techniques.

Some good sources of info include:

Varnishing Wood
Shop Talk
Applying Varnish
Epifanes Q&A
Fast and Fabulous

Remember that varnishing, like all other finishing, is 90% prep and 10% application...

[IRGuy]

Matt...

I wouldn't ever question any suggestions or comments made by the likes of Buju or Captain Pat, both of whom's recommendations have helped me immensely in my rebuild of "Phoenix", but if I can be allowed to add a small comment to those above I would say that whenever I varnish anything I dilute the pure varnish about 10-15% with the recommended thinner for the first coat. Let it dry well and then sand lightly with 220 or finer paper to remove any of the roughness caused by the small wood fibers that raise. Clean the surface well by vacuum cleaner and solvent wipe, then wipe with a tack rag. I find this seals the wood plus provides a smooth base for the following coats.

Capt Pat...

Thanks for the above info sources.

Matt again...

After making my original post I went to all the sites Capt Pat suggested, and found the following on Epifanes site...

Question: I am experiencing air bubbles drying in my varnish.

Answer: We will bet that what you are experiencing is dust. Dust and/or lint particles that dry in the varnish can form tiny craters that can certainly look like air bubbles. It is very rare for air to dry in a coat of varnish. Let's try to figure out where this dust might be coming from. If the coat looks great upon completion but several hours’ later looks as if someone has taken a saltshaker to your boat, then the dust problem is most likely airborne. If the dust occurs right away, brushes and the initial cleanliness of the surface are more likely to be the culprits. Here are a few, sometimes overlooked, sources of dust; • Although your brush may appear clean, try flicking the bristles in front of a bright lamp. You will be amazed at what comes out of it. Turn on the TV and be patient. It can take an hour. Do not assume that a new brush is clean, new brushes are particularly dusty. • Be aware of what is happening overhead, it may be that your basement ceiling is shedding dust each time someone crosses the room upstairs. • Fluorescent lights will act as a dust magnet until the moment you turn them off. • Check your clothing. Wear dampened Tyvek coveralls. • Mask or temporarily seal all screw holes. Your brush will certainly pull out whatever is hiding in those holes. We know a painter that varnishes in the nude listening to Vivaldi. Hey, whatever works.

This pretty much follows the posts by Buju and Capt Pat.. but the thought of either of them working in their shop naked with a varnish brush in their hand is sort of kinky to me! Gotta go with the flow I suppose.

[Buju]

Ha! and ya'll thought I was wearing bottoms in my avatar photo...

No seriously though, if it aint showing up until the 3rd of 4th coat, then I'd put all my money on a not thoroughly cleaned brush.
When you get the brush back out, if it has stiff bristles at all, that is dried varnish on the bristle. Once you work the brush so that it's pliable again, you just created thousands of tiny loose particles which will get in your next coat.
It cannot be effectively cleaned either. You can work/comb/and beat the hell outta it, but that just stresses the bristle, and it'll begin to shed. The brush is toast... as a finish varnish brush anyways. Still great for oil primers and whatnot around the house.
Sand it down (220- unless it's large bubbles/pits, then 120/220) wipe it clean, and reapply with a new white china brush, presaturated as Capt. Pat described.

Unless it showed in the first coat... or if the bubbles are actually fisheye...
Pic would help.

[amuh60]

For the first 4 coats I used the throw away foam brushes that did a great job of laying the varnish on smooth, bubble and dirt free. Furthermore, my first few coats were very thin until I knew I had the grain sealed. I am a newboy though and got all my info from advice and reading everything on this site plus talking to Epifanes on the phone.

-Andy

[IRGuy]

Buju...
I never thought about the issue of a stiff brush letting loose lots of dried varnish particles when it is flexed to make it soft again. I have learned a lot today! Thanks

[ianupton]

I always thought you wanted to varnish when the temp was falling (wood warmer than surrounding air) such that the cooling wood would draw in and NOT cause bubbles. In fact, I had thougt you should put a peice out in the sun to warm it up, then move it to the shade to varnish.

I guess I was in the wrong...

I learn something new everyday.

Ian.

[coolair]

Thanks Guys,
as I read, the light comes on! I did have a new brush, and it didnt start showing up untill 4th or so coat. The early ones i put on with the cheap foam brushes, and the more i look at it, the more i think its dust, I dont have a camera at my shop that will take a good enough picture. I will try later on. And i will get rid of the denatured alcohol, i was thinking it was better than acetone, Like you said a very steep learning curve! Buju it is pettit 1015, which i dont really know of what qaulity the stuff is, and it says it doesnt need to be thinned for brushing. I know everyone uses epifanes. Its what the guy recomended and he seemed pretty knowledgeable. First piece of wood i have ever varnished, I know that my shop is by no means clean, and dust free.

[coolair]

here r some pics there r more on photo bucket

http://s967.photobucket.com/albums/ae15 ... 20project/

[Buju]

Yeah, it looks like you've got junk in your finish... particles of dirt, dust, dried varnish, etc. Whether it came from the air, or brush, or in the varnish.
Looks like it also concentrated near the ends of the trim, meaning that you're carrying it/ spreading it with the brush and as you near the end of the piece, you let up the pressure on the brushstroke, which allow the contaminents to release from the bristle/foam and deposit themselves in the finish.

Sand the bad areas lightly with 120.
Follow up everywhere with 220.
Vaccum.
Wipe with a spirits saturated rag or tack rag.
Reapply strained varnish with a new, clean, pre-saturated brush.

BTW, The Petit 1015 is great in my experience. Doesn't get much respect, but I think it's UV resistance is excellent, and the abrasion reistance is good, while retaining a fair amount of elasticity. I like to topcoat the Epifanes Rapidclear with the 1015...

[coolair]

Buju, Capt. Pat and everyone
Thanks for all the info, the more i read, the more i see how i was doing it all wrong! I wasn't puting a whole lot of varnish on my brush, so i got that right, and all the sanding and cleaning other than the type of cleaner, but i was dipping from the can, piece is so small only need a little bit to cover. But that is whats so great about this site, and these boats. I am learning more everyday.
Thanks guys for all of the great info. Though it has a bunch of crap on my final coat, i am excited at the results and what they will be when i get it right.
I like the the shop talk, and how its a Zen process. I need the stress relief!
Thank you again.