Thinning water based poly?

[Kerry in Fort Sask, AB]

I've rarely used waterbased poly before, but wanted to use up a can of Varathane Diamond polyurethane that I bought a while ago. I find that even though I gently stir it and take care to lay it on as smoothly as I can and not work it too much that I get a gazillion tiny tiny bubbles all over the surface. I remember this was what happened when I used it the first time as well. I do tip-off the work right after laying the finish on, and it helps a little but then it seems the bubbles re-form. I'm wondering if I can thin it with water to increase flow-out? I know I can just try it but I figure someone here must have tried it already. There's no mention on the can of thinning this finish.

Kerry

[Greg Bainbridge]

What are you applying it with?

[Kerry in Fort Sask, AB]

What are you applying it with?

A polyester fibre brush.

Kerry

[ArtMulder]

Odd. I use flecto varathane regularly. I've never thinned it.

I use a foam brush. And you can't "work it" at all. I lay it down, and maybe drag the brush back over it once, and that is it. The first coat is very rough, due to raising the grain. Give it a light sanding with 220. Second coat is better. third coat's the charm.

[Frank D.]

I've had that problem when doing details. I tried a ton of solutions, including changing brands, special pad applicators and thinning (I tried foam brushes too--that was the worst for me because the foam made tons of bubbles...just my experience). With the brands I used (most were common ones found at big box stores: Varathane, Minwax. etc.) it was maximum 10% water. I finally gave up on all the fancy solutions, bought a good synthetic brush, and improved my technique. For me everything was in feathering out the finish--quickly!--after flooding the surface. Now I hardly get any bubbles at all (a few here and there, but nothing too noticeable). Of course the flatter and smaller the surfaces are, the easier it is to apply. The more detail, the more bubbles. If you,re anything like me, I'd say stick with it and you should see improvements if you concentrate on improving your technique. Of course the more expensive varnish does give better results on the whole (Merlin, Oxford), but even then good technique is still important.
FWIW

[Chris Fournier]

Use some water and Floetrol. Floetrol helps to break surface tension and also helps the finish flow. You can get this stuff anywhere.

[Greg Bainbridge]

I like water based poly. I have found the best results using a foam brush. However you need to find good foam brushes. There are foam brushes that look somewhat like an aero bar, and then there are those that have very fine pores. Those are the ones that work for me. The trick for me is to apply the finish very slowly. After you apply say 2 coats, and clean off the top with a scotchbrite pad, load the brush, and then vary your speed of application, without stopping, without a second pass over the same spot. I think you will find the speed that leaves very few, or no bubbles. For me it would be about 15 seconds to go 12 inches. Hope this helps, or works for you.
Greg

[Max In Sudbury]

Hi Kerry,

I've used the Varathane water-based a number of times but have sinced moved on to spray lacquers. With the varathane, I usually had to thin 10% with distilled water (don't use tap water due to the minerals in tap water). I used a foam brush - the better ones will cost a few dollars each - don't use the ones that are 20 for a dollar - they seem to produce larger sized bubbles as the foam is less dense.

Try to apply with the grain, keep the brush wet, and stirred, not shaken. Don't overwork the surface by tryingto get rid o fthe bubbles.

Now - from my experience, if the bubbles are really small - where you can't tell if they're dust or bubbles - they tend to disappear as the finish cures. Lightly sand between coats if you need to remove dust/bubbles and apply the last coat the thinnest.

Try a test piece going only in one direction (with grain) and let the bubbles dry and see if the bubbles disappear.

Max

[Kerry in Fort Sask, AB]

Hmmmm, I'll have to see if I can find a good foam brush, and maybe some Floetrol. Sounds like I should be safe to add 10% or so of water, so I may try that first with my current brush and see how that works. If nothing else, this makes me appreciate shellac even more :lol:

Thanks for the input you guys, I appreciate it.
Kerry

[ArtMulder]

I like water based poly. I have found the best results using a foam brush. However you need to find good foam brushes.

I used a foam brush - the better ones will cost a few dollars each - don't use the ones that are 20 for a dollar - they seem to produce larger sized bubbles as the foam is less dense.

That's funny. There must be something to my technique then. As I just use bunches of cheap foam brushes (like these from LVT) and the results are fine. And I've never thinned, or used Floetrol.

You're not squeezing the brush on the side of the can, are you? I dip in in about 1/2-2/3. Lift it up and let it drip out the excess. Give it a very light twitch (not really a shake) and then lay it on the piece.

[Max In Sudbury]

Hi Art,

I don't think I'd consider the LVT brushes as cheap - but I've never used them. I use brushes from Sherwin Williams or BenMoore which are denser.

As for the cheap ones, I've purchased a bunch at the PriceWise (think dollar store) and Home Harware bulk - and they weren't very good. The created bubbles, and broke up real quick. Same technique - different results.

If you have success with yours - great!

Max

[Kerry in Fort Sask, AB]

That's funny. There must be something to my technique then. As I just use bunches of cheap foam brushes (like these from LVT) and the results are fine. And I've never thinned, or used Floetrol.

You're not squeezing the brush on the side of the can, are you? I dip in in about 1/2-2/3. Lift it up and let it drip out the excess. Give it a very light twitch (not really a shake) and then lay it on the piece.

Hi Art,

No, I've been careful not to touch the brush to the can. I recalled that from a book I read.

Kerry

[John in Calgary]

That's funny. There must be something to my technique then. As I just use bunches of cheap foam brushes (like these from LVT) and the results are fine. And I've never thinned, or used Floetrol.

You're not squeezing the brush on the side of the can, are you? I dip in in about 1/2-2/3. Lift it up and let it drip out the excess. Give it a very light twitch (not really a shake) and then lay it on the piece.

I'm with Art - I don't use anything but the brushes in the bin at our local Totem and I don't have any issue with bubbles except when I let the finish roll around corners and don't clean up the extra (the bubbles form in the blob around the corner). Technique is to stir with a stir stick, dip the foam brush, let the excess drip off, then flow it out on your piece. Don't work it too much (although on smaller or less complex pieces I will go back over it to give it a brush from end to end with the brush verticle to the surface to top the finish). My finishing is all done in our unfinished basement, so maybe the cooler temperature helps.

John

[mreza]

I'm using the same product and I'm applying it with a good bristle bruch. I don't get bubbles but I find the product too thick to flow smoothly, especially that the piece I'm applying has turned posts (beeds, coves, etc).
So I'm thinking about thining it (for the above mentioned reason). Did you just use water and what was the results?

[Kerry in Fort Sask, AB]

I'm using the same product and I'm applying it with a good bristle bruch. I don't get bubbles but I find the product too thick to flow smoothly, especially that the piece I'm applying has turned posts (beeds, coves, etc).
So I'm thinking about thining it (for the above mentioned reason). Did you just use water and what was the results?

Yes, I just used distilled water. It seemed to flow a little better, with fewer bubbles, but I still had quite a few. I didn't use a very good brush. I only have one really good one and it's dedicated to shellac. I tried using a foam brush and that also helped a little I thought. Maybe I'll have to buy another good bristle one some day and give that a try.

Cheers,
Kerry

[Julian]

Hi Kerry,
Much as it is praiseworthy to desire to use up an old can of something you bought in the distant and foggy past which may well be past its shelf life and anyhow you never liked it or you would have used it earlier.......the reality of it is that this is a nasty fussy product and not worth the aggro, the time spent trying to improve your technique or the uwarranted expense of all sorts of superior brushes or application devices that may (or may not) help.

Why not cut to the chase, throw out the horrible stuff and get some of your favorite finish ...and use that!

I would!

The results will speak for themselves!

Be happy!

Bye for now
Julian

[Kerry in Fort Sask, AB]

Hi Kerry,
Much as it is praiseworthy to desire to use up an old can of something you bought in the distant and foggy past which may well be past its shelf life and anyhow you never liked it or you would have used it earlier.......the reality of it is that this is a nasty fussy product and not worth the aggro, the time spent trying to improve your technique or the uwarranted expense of all sorts of superior brushes or application devices that may (or may not) help.

Why not cut to the chase, throw out the horrible stuff and get some of your favorite finish ...and use that!

I would!

The results will speak for themselves!

Be happy!

Bye for now
Julian

Thanks Julian, I know you're right, but it's half a can! Why, that's at least $5.00! :lol:

You are absolutely correct though and I am going to discard this leftover stuff. I will try some other water based poly sometime though. With a basement shop it would sure be nice to cut down on the solvent vapours for health reasons.

Cheers,
Kerry

[Kerry in Fort Sask, AB]

Yesterday I took Julian's advice and picked up a new can of waterbased poly. This time I got Minwax Polycryl. This material goes on much nicer than the old can of Varathane I was using. I've tried it both with a foam brush and a bristle brush and either way I don't get the bubbles like I did before.

Kerry

[Paul O in Paris]

With a basement shop it would sure be nice to cut down on the solvent vapours for health reasons.

Don't get lulled into a false sense of security by the very slick advertising that goes along with waterbased finishes. The only major safety advantage they have over solvent based is that the carrier is not explosive, and in a basement shop that is a huge plus. There are some pretty nasty chemicals in waterbased finishes which shouldn't be breathed and can cause furnace burners to deteriorate quickly. There's a lot of hype about VOC's and HAPs, but glycol ethers are not kind to your internal organs, and because current legislation is focussed on solvent based compounds, the wb manufacturers do not have to list everything that goes in their products, so you don't know what you're breathing.

regards..............Paul

[Lost in the Woods]

Hi Kerry,
Much as it is praiseworthy to desire to use up an old can of something you bought in the distant and foggy past which may well be past its shelf life and anyhow you never liked it or you would have used it earlier.......
Julian

I had been told a long time ago, that once opened they should be used within six months. I just can't recall whether this applied to only the regular Varathane or the WB one as well.

Hate throwing out anything myself, but I once recall someone on this forum in the past mentioning how nuts it is to potentially ruin your fine work trying to save a few dollars on what would likely be a bad finish. Wise words we need to hear from someone else sometimes rather than the little voice in our heads no matter how loud it's screaming at us.