No bubbles or brush marks with water borne finishes

[Chuck Morrison]

I've been trying to brush PolyAcrylic finishes for almost as long as they've existed in a belated attempt to escape the health hazards of lacquers. After several recent instruments finished with shellac (French polish) I went back to PolyAcrylic (Brite Tone) to use its high solids content for grain fill. As usual, I had a problem with bubbles and brush marks so I consulted the internet, yet again. This time I found a video by an artist who uses it over oil paintings. Her technique was so bizarre that I had to try it. I was surprised to find that it worked, giving me the flattest finish coats I've ever had brushing water borne finishes.

The technique is simply wetting the surface with water and brushing the finish on while the surface is still wet. I've tried it several times and refined the technique a bit. I start this after the first coat is in place (over a shellac sealer coat) and dry. I knock off any dust or bubbles with 600 or higher grit sandpaper and vacuum the dust off. Then I use a damp cloth or paper towel to get the rest of the dust off.

At this point I wet a clean cloth or new paper towel, not dripping, but more than just damp. I wipe the surface, coating it with a thin sheen of water and quickly brush on the finish before it drys. It's best if the brush (or sponge) isn't over loaded with finish, using thin coats. I lightly and quickly over-brush (once) to reduce bubbles and smooth out any thick areas. Within a few minutes the bubbles are gone, at least mostly. The resulting dry surface has with few, if any bubbles and no brush marks. The surface is flat and not as glossy as if brushed over a dry surface. This has reduced the number of coats I have to put on and the amount of sanding I have to do to get things flat.

I think what is happening is that the finish flows easier across the water than a dry surface so it flattens brush marks. I don't know why the bubbles pop so much better. Maybe it reduces the surface tension enough to pop the bubbles, or maybe it's just wetter longer. You would think that thinning the finish with water would serve the same purpose, but that has not been my experience.

[Dick Hutchings]

Very interesting and thanks for sharing your experience.

[Barry Daniels]

Instead of wiping the water on, what about a light mister squeeze bottle? It might leave a more evenly coated wet surface.

[Chuck Morrison]

I tried misting the water first. I wanted as close to an even coat of water as I could get and my misting bottle wasn't doing that and I had to wipe it anyway, so I went with wiping without misting.

[David King]

I wonder if wiping with a compatible retarder would also work and evaporate more slowly than just plain water.

Meanwhile i keep hoping I'll stumble into a way of applying shellac so that it doesn't pool up around the edges (and dragging any color tint with it.)

[Clay Schaeffer]

Do you think the wetted surface that helps flow out might also affect the adhesion of the film? I would be curious to know.

[Christ Kacoyannakis]

Very interesting Chuck. Do you use the same technique between each coat? How many coats do you find you need with this technique?

[Chuck Morrison]

Do you think the wetted surface that helps flow out might also affect the adhesion of the film? I would be curious to know.

I'm curious to know as well. Just from working with it on one instrument it doesn't seem to be a problem, but time will tell.

[Chuck Morrison]

Very interesting Chuck. Do you use the same technique between each coat? How many coats do you find you need with this technique?

Yes, I do. I think a fair part of this is that wiping on the water also wipes off any remaining dust, which helps it all lay down nicely, not as many dust nubs. So doing it every time helps with a smoother finish coat. I usually sand down w/400 grit between coats unless I get lazy, in which case I just coat directly over the previous coat if it's within an hour or two after the previous coat.

As far as numbers of coats, that depends on how much I load up the brush/sponge. I usually try for 6 coats, and with this technique I hope to do so with thinner coats. If I'm using the finish for pore filling it can be 3 or 4 more coats extra on the back/sides/neck.