Help with texture in sprayed varnish

[Sebastien La Madeleine]

I don't know where to start. I've been on this problem for the better part of 3 months.

I am building a series of bed sets for my kids. For the first one, I used water based stain and sprayed some satin saman ( www.saman.ca ) varnish and it went on smooth and even, not perfect but good enough.

For the second kid, the color needed to be more vibrant so I switched to Behlen Solar-Lux for the stain and was recommended EM1000 for sealer and EM9000 for finish, satin again.

Being that I'm not the quickest, there was almost a year between purchasing the product and using it. The stain went on nice albeit being faded without finish. Then the sealer unevened the stain and the varnish cratered on me.... I found a couple of references online stating that EM9000 will actually crater after sitting on shelf for a few months...

I gave up and sanded back to wood, restained with the Solar-Lux and tried to varnish with Saman. This time the color is fantastic. I sprayed 3 coats of gloss varnish and then added a coat of satin. The 3 coats of gloss went on really nice and even. The coat of satin was a disaster. It feels like sand was spread in the finish.

For the last two weeks I've been trying to tweek the way I lay it down and no luck!

I built a spray booth (with a fan and filters), cleaned all of my compressor lines, added a filter right before the gun. I tried to spray with 25psi, 20psi, 15psi, 1.5mm, 1.7mm, 1.9mm, switched gun, hose. I changed for a new can of varnish. Today I even went and bought Varathane Diamond Clear and got a similar result.

Here's the process, I hope someone can help me pin point where I go wrong!

-Sand the birch up to 150
-Spray Solar-Lux
-Let dry for 1hr
-Spray gloss Saman wet coat (pretty much all absorbed instantly)
-Wait 1hr
-Spray gloss Saman wet coat
-Wait 1hr
-Sand with 220 or 320 until flat and even
-Spray air then wipe with dry rag
-Spray gloss Saman wet coat
At this point it looks great and not too rough
Wait an 1hr or overnight
-Sand with 320 until flat and even
-Spray air then wipe with dry rag also tried wet rag
-Spray with Saman or Varathane satin
-Open hells gate and throw the whole thing in the fire
At that point it feels like sand in the finish no matter what I tried.

I also tried on different test pieces and I can reproduce the problem... I can't seem to get it right anymore...

Gloss
gloss.jpg
Satin
satin.jpg

In the pictures you can see the gloss coming out nice. In the satin, you can see the bumps in the light reflection...

Any idea welcome!
Thanks,
Sébastien

[Wayne Lomman]

Sebastien, a couple of things to try. Check your spray gun set up as it could be dry spraying. This can be caused by blocked vent holes in the cup or blocked airways in the air cap.

You may be spraying too light a coat that is unable to bury/absorb the remnants of sanding dust. This depends on the coating material as some dissolve their dust and others don't.

Others will have more ideas but this is a start. Cheers

[John TenEyck]

Try your whole finishing process on some scrap with a brush instead of spraying it. If it still gives you that sandy look then you'll know it's a problem with your prep. work or something related to the finishing products. If it comes out perfectly smooth then you'll know the problem is related to spraying.

John

[Sebastien La Madeleine]

Thanks for the ideas!

I did make sure I was not dry spraying, I did try thinner and thicker coats (up to 6mil) and swapped to another spray gun.

I will definitely try it with a brush to make sure it's not spray related. Having had success spraying in the past, I never thought of going back to a brush.

I spoke with the manufacturer rep and she suggested that sanding to a rougher finish might help too.

Thanks again!
Sébastien

[Sebastien La Madeleine]

No luck.

I bought a brand new brush, layed it on wet on freshly sanded pieces with 220grit and not only did I get similar specks I can now see the sanding scratches and brushing strokes, not overly so but it definitely does not look as nice.

I keep having to remind myself that this is just a test.

At this point I just want to find a way to put the varnish on and have it semi decent to finish that piece of furniture and move on.

I think I will follow the method in this thread:
http://www.sawmillcreek.org/showthre...-with-your-ROS

My only concern is to over polish or to produce uneven sheen...

Thanks for the help!

[John TenEyck]

Well that's disappointing, but tells us that the problem is not with your spraying. It has to be an incompatibility problem between the gloss Saman and the satin products. Oh, which satin product did you use, the Saman or the Varathane? Try it with the other. If it still happens, then you'll know you can't put either one over the gloss.

Have you tried just using the satin? Does the same thing happen or does it only happen when you put it over the gloss?

John

[Sebastien La Madeleine]

I tried with the Saman product. I will give the Varathane one a shot, good idea.

I did not try to use just satin through and through because I did in the past and it kind of leaves a white hue from all those flattening agents cumulating through the coats. I will this time around though.

One thing I did ask the rep and she confirmed that both Satin and Gloss are the same, only the satin contains matting agents that will lower the sheen.

Off to the workshop!

Thanks again!

[John TenEyck]

Ahhh; I just realized you said at the very beginning that the Saman products were nearly a year old before you used them. Right? I wonder if the flatters in the satin have agglomerated and that's what's causing your problem? If so, you should get good results with fresh product.

John

[Sebastien La Madeleine]

The Saman product was actually fresh from the store (manufacture date 09/2016), the EM9000 was not. And I actually bought a new can to make sure it wasn't just a bad can.

I did try the Varathane and same results.

I spent the day today cleaning the whole finishing room... I tried to see particles of dust in the sunlight before and there was none, so I don't think it's dust but figured I'm so desperate at this point that I just figured I'd clean it again...

I'm waiting for the rep to come inspect the work and hopefully resolve the issue but I also ordered some white and gray pads to polish it if nothing is found problematic...

Thanks for all the help!
Sébastien

[John TenEyck]

What happens if you just start with the satin product (your choice of which one), and leave out the gloss?

John

[Sebastien La Madeleine]

I will try this on freshly sanded wood as well to eliminate the possibility of incompatibility with the Solar-Lux as well.

Thanks so much for the stream of continuous ideas.
Sébastien