Bubbles

[Victor]

I did everything I could think of - sqeegeeing out the brush in fresh paint thinner before dipping it in the varnish, using thinned varnish, using straight varnish, putting it on thick, putting it on thin, but I still get a brush full of tiny (*&^%$ air bubbles every time I dip it in the can! Grrrrrr! Having the piece vertical seems to help a little. I'm never gonna get this right. :(

[Bob Smalser]

You sure it's the brush?

Some woods offgas considerably with certain finish materials during the first coat.

[Victor]

This old cedar is sucking it in like a sponge, but when I squeegee the brush in the fresh paint thinner I get a slew of bubbles. Foam brushes do the same thing.

[TimH]

You need to mess with the brush as little as possible. Just dip it in the varnish, dont scrape the brush on the side of the can or anything, just apply the varnish to the wood slowly and in one direction....the idea is to APPLY the varnish to the surface, not to BRUSH it on. Also try top brush over the same area as little as possible. Brush slowly enough that the varnish has time to flow off of the brush in one stroke if possible.

[George Roberts]

I use a paper towel but ...

It takes experience to balance the varnish, thinners, driers, brush. and brush technique.

When I brush, I just add thinner until the bubbles break before the thinner evaporates.

[Wild Wassa]

Was the wood in the sun, or have you moved the section that is drying into the sun?

Following Bob thoughts, and if it is too late to use George's technique. Heating the surface or wood after painting forces out gassing and the air bubbles in the paint will expand. This can appear quickly or more likely, an hour or two later, which is always after the skinning has started. If it is only the first coat over unsealed timber you must expect some gassing. Key the surface which ruptures the bubbles and recoat. If you are painting over what you thought were filled or repaired cracks in ply or solid timber, you might find these areas can out gass for a few coats.

A coat or two of CPES before painting I find, will drag out the gass very early in the process. One of the immediate benefits of using CPES I find.

Warren.

[ 07-25-2004, 07:54 PM: Message edited by: Wild Wassa ]

[Victor]

Usng a larger brush helped, but even a big brush won't hold enough varnish to cover the whole piece in one stroke unless it's very small. These bubbles aren't from outgassing, they're from the brush. Should let the varnish sit a while after pouring it from the can into the container, and thin enough so that the brush marks level themselves, is that right? Could get some more CPES I guess.

What do you use a paper towel for?

I've been wetsanding between coats, is that right? How much can you expect the next coat to fill in brush marks from the last coat?

[Wild Wassa]

I don't think painting works like that Vic, concerning the brush marks, unless you are using a polyurethane (whick has an ability to remain a build coat). Most brush marks with most materials telegraph through to the next coat. If you are after quality cut them back early.

At the painting stage, one does not normally consider paint to be a stage in a build coat process. Problems arrise when you attempt to build up paint (excluding BCP's Aquacoat polyurethane I find) it doesn't have to be an overly thick application for problems like orange peel textures, or crows feet textures to take over.

To me it sounds like your paint is too thick. Many thin coats are better than a few thick coats.

Paper towel, to wipe away problems. I like to buy lintless painters rags. 6kg of painters rags costs about $10US over here.

Warren.

ps, The last bag of painters rags that I purchased are cut up wedding dresses. It doesn't seem right.

[ 07-30-2004, 01:21 AM: Message edited by: Wild Wassa ]

[Scott Rosen]

What sort of brush are you using?

What are decanting the varnish into? You're not dipping the brush directly in the can, I hope.

[Victor]

Sorry Warren, I'm revealing my ignorance. How do you apply a thin coat without painting it on? As opposed to letting it "come off the brush", which implies a thick coat. And what do you do with the cloth? Wipe the brush marks off? I never was any good at this.

[Wild Wassa]

Vic, Wiping is not flattening the paint. Wiping away, is totally removing any bad results, wipe the paint right off the surface if you have problems, be aggressive.

Thinning the paint with solvents, or adding oil, is crucial or using a flow control medium like Penetrol for adding to oil based paints (or Floetrol for water based materials) is a real aid to painters. It will turn you into a pro painter. Very rarely will paint come out of a can in a ready to use state, I find, often paint is far too thick. This is the real skill, thinning the paint with out overly thinning it. I don't use cheap linseed oil, I like oil artefact free. Ages ago I purchased the best I could find.

Having the paint/varnish at a room temperature (68F), or just under, helps the flow and allowing the paint to dry slowly so that any inherent levelling characteristics that the paint may possess, are able to work.

Using the highest quality brush that you can afford determines the surface quality. The finer the bristle the finer the quality. When I start painting a surface I don't expect that things will even look half descent until the 4th coat goes on. The paint needs to be on paint before it gets its act together, paint nurtures paint, I find.

Selecting a brush that suits your paint (if you are not spraying, I don't spray) is the move most painters overlook. Purdy in Oregon (amongst others) make a range of fine hand crafted professional brushes, to suit the different paint types. Have a look at their site and the other pro brush makers sites. For my hack work, I like a Purdy Elite Pro, Purdy also make a Super Elite Pro brush, and for varnish they make a Fine White China Bristle brush. I use a Japanese fine white bristle. I don't use a foam brush it aerates the paint and gives bubbles, as you have noticed.

Making sure that your key/scratch pattern on the last coat is uniform before recoating, this determines the draw of the paint from the brush, and again is much overlooked, when it comes to the quality of draw from the brush. I cut and key the layers, with wet and dry (to keep the dust down) starting at #220 for the first coat or two, #320 for the next two coats, then #400 for the next, however many coats. A good varnish job will have over half a dozen coats. Real hot finishes have more.

Don't over stroke your paint, this can bring oils to the top with oil based paints and varnish, which will give different gloss levels on the surface, and when you paint let your brush lift from the paint at the end of your stroke. Don't deliberately terminate the stroke, otherwise you will get overlaps and steps, and finally, always stroke back into the wet paint, so that the paint can level itself. I find that three brush strokes with varnish is about right for me, 4 at the most.

Warren.

[ 07-25-2004, 09:27 PM: Message edited by: Wild Wassa ]

[Victor]

I bought a fancy-schmancy China brush from the Wooden Boat Store, but that didn't seem to work any better than a decent ten-dollar brush from the hardware store. I'm getting there. I decant into a clean plastic dish, let it sit for a few inutes to lose the bubbles, then put it on thin enough for the brush marks to flatten. Still has a few bubbles and dirt specks, so I wet sand. Besides, this ain't no showoff boat, it's a workinman's barge. Only God is perfect. smile.gif

[ 07-25-2004, 08:37 PM: Message edited by: Victor ]

[Concordia..41]

Victor, Victor, Victor...as stated, the brush is the medium that moves the varnish from the container (not the can it came in) to the wood.

Don't wipe the brush out on the side of the container. Just dip the brush into the varnish and allow it to wick up into the brush for a moment, then apply to the wood. I'm a foam brush fan (also have a good set, but I'm too lazy to clean them), but the theory is the same.

If you're getting bubbles regardless - several coats later - you're most likely pressing the brush down as you stroke. Air bubbles come from air - either outgassing if the wood is in the sun or from air introduced into the varnish.

If you're not doing so, try adding your thinner - (which shouldn't be needed after the first couple of coats) in a clear container. This will allow you to look at the varnish and if you've stirred in the thinner egg beater style you can see the air bubbles work their way to the surface.

What brand of varnish are you using? Some are pickier than others, but none should spontaneously produce air bubbles - no matter how deviant a life you've led ;)

The purpose of sanding between coats is to rough up the surface of the varnish so that the next coat adhers to the previous. What you're doing is BUILDING coats and then leveling.

Take a pen or pencil and draw some short up and down lines like the tooth of a comb. (This is your wood grain when viewed from the end). Now take a different color pen and follow along the top of the peaks and valleys you just drew. (This is your first coat of varnish.) Do the same thing with another color. (This is your second coat of varnish.) Notice how with each color/coat, you fill in the valleys, but you also raise the peaks. I haven't worked with much cedar, but most woods take a minimum of five coats before the valleys fill in to the level of the original peaks.

Now you're in the varnish business. And now you can work at leveling off the build up on the top of the peaks and continuing to build a flat varnish surface.

Make sense?

- M

[Dave Fleming]

YIPEEEEEEE!

Margo is BACK!!!!!!!!

:D :D :D :D :D :D

edited to add more Smileys
:D

[ 07-25-2004, 09:26 PM: Message edited by: Dave Fleming ]

[Wild Wassa]

Victor, how do you stir you varnish? I hope you don't shake it like I would with an acrylic house paint.

When I stir varnish I stir/blend it, somewhat slowly, with a perforated paint stirer. This type of stirer allows me blend quickly without mixing too much air with the paint.

Could you be using an oil and polyurethane blend varnish? ... rather than a straight oil based varnish. This type of varnish skin somewhat quickly, painted on warm timber they are deadly.

Warren.

[ 07-25-2004, 09:41 PM: Message edited by: Wild Wassa ]

[Steve Miller]

I don't stir varnish too much but do use a paint filter to take any crud, lint, bugs etc out. Seems to take bubbles from stirring out too. Penetrol will save your life on varnish. I like 2 - 3 ounces per quart of varnish. I have been using Interlux Schooner. Good luck.

[Steve Miller]

I should have added: cone shape paper paint filters that have the cheese cloth at the tip of the cone. Sort of look like coffee filters. Available at any paint store, big box home center or any place that sells Penetrol to save you a trip.

[Victor]

Finnaren & Haley at the moment. I stir slowly. I really think the bubbles form on the bristles as soon as they hit the varnish.

[ 07-25-2004, 10:18 PM: Message edited by: Victor ]

[Scott Rosen]

Something seems wrong. Maybe you're getting dirt and dust, not bubbles. Small bubbles almost always pop before the varnish sets up, so even if you have bubbles, they shouldn't show in the cured finish.

When I get bubbles, I remove them in the "tipping" process. That always works, unless the bubbles are from outgassing of the wood. And that only happens on the first and maybe the second coats.

After you apply the varnish (or paint), you should tip off the surfaces with a very light stroke of the brush, in one direction. This helps the leveling and eliminates any bubbles.

If all else fails, find a professional boat painter and watch him/her work.

[Tom Lathrop]

I agree with Scott. The latest varnish formulations that I use don't give any bubble problems and I ain't no varnish expert. Never varnish or epoxy on a porus surface that is warming up. This will guarantee outgasing and bubbles.

Now if someone can tell me how to eliminate dust in a practical way, life will be more simple.

[Corso]

Tom: no pratical (cheap and easy) way to remove dust in the air, even if i seemed to notice that swearing at it just attracts more :rolleyes: .

I totally agree with everything Concordia41 said.
It looks like the main problem people has varnishing hardwood floors with poly, if there is a bubble it will stay, sand and re-finish the spot and youll likely see the patch.
The major mistake seems to be the wiping the brush on the side of the can to drop the eccess of varnish, that just put bubbles everywhere in the can and youll end picking them up as they are.
For a quick "how to" you can get the little panphlets that Minwax has in any hardware/paint store, some tips are there, in any more serious manual about DIY floor painting youll find great tips on avoiding bubbles.

One thought on brushes: i have a friend in Italy that makes guitars, he buys cheap brushes , nothing fancy, and most of the times make them himself, as long as they dont loose hair they are fine, and the varnish on a guitar cant be anything else than perfect or the instrument goes in the trash. Of course seeing him painting is as amazing than listening to him playing smile.gif

[Wild Wassa]

Victor, When you get bubbles (now that I'm a bubble making expert, I got hundreds per stroke today, both the paint the air temp are a bit cool), just swiff the varnish with a hair dryer set on a medium flow and the temperature set to low. Heat guns can be a bit powerful for bubble busting, even when set to cool.

A hair dryer will fix a bubble problem. If not thin the varnish just a tad more. With a varnish straight out of the tin, normally I thin the varnish just a tad but today I didn't, I was able to create the bubble problem very easily.

Warren.

[ 07-30-2004, 03:30 AM: Message edited by: Wild Wassa ]

[Nicholas Carey]

I've been using this pointed, round hogshair brush by Isabey (France). The trade name is "Elephant".

http://www.danielsmith.com/images/p12941b.JPG

I got from Daniel Smith's Artist Supplies (http://www.danielsmith.com/)).

It's pretty reasonably priced (e.g., $15) and it flows well — it doesn't put down a huge amount of varnish — for what I'm doing (companionway ladder—lots of inside corners, etc.)

They have lots of different types/si zes (http://www.danielsmith.com/cgi-bin/sgsh0113.exe?FNM=00&CATG=INFO+EBIE&UID=2004073015532198&UREQA=1&GENP=) available.

I still tip off with a dry foam brush, though.

[Divine Wind]

thin the varnish to 40% and then use a paint pad to apply and feather in the normal way across the grain and then along it. Any bubbles will pop as soon as feathering is done.
regards, harry(divine)

[Victor]

How about heating the brush and/or the varnish?

[Wild Wassa]

Heating the varnish is a good idea but no more than 22C, when spraying some painters like temps as high as 30C.

I water bath both paint and epoxy. And cool bath them as well, especially the water based polyurethanes that can skin in a matter of seconds during summer. The day temperature can sit close to 40C for long periods of time here in Canberra.

My bubble issues came from playing with the varnish. I continually try to refine my embossed varnish anti-skids, I'm trying Norglass Weatherfast Marine varnish at the moment and have been for a few months, it is a fine varnish. Before Norglass I was into Cabot's Marine varnish oil/poly blend, which I find too thin for an embossed anti skid, without thickening it, which defeats the purpose. I think Norglass is the class act in Oz.

Norglass Weatherfast's varnish colour is neutral (so far) and close to the transparency found in a clear poly, than the traditional warmth and density found in an oil based varnish.

Warren.

[ 07-31-2004, 01:32 AM: Message edited by: Wild Wassa ]