Troubleshooting Shiny Paint

      until the "flatting" agent left too much sheen. Finishers share ideas about what might have happened, and how to fix it. June 28, 2005

I am working on a large pool house that is lined with interior walls and has a ceiling with old pine boards. The boards were belt sanded clean to remove old paint and left to look rustic. In keeping with the rustic, yet functional plan, a painting contractor sprayed on (with an airless) one coat of vinyl sealer and two coats of lacquer that was the factory flat sheen, with a quart of flatting (or flattening) added to each 5 gallon pail.

We were expecting an 8-12 degree sheen, but it has been dry for several days now, and looks like a 35-40 sheen. We took some of the topcoat and put it on glass and of course, it came out dull as we expected. I do not know the dry film thickness on the pine boards, but the flatting (or flattening) should still be effective shouldn't it? Will another coat fix it? There are still two more rooms to spray.

Forum Responses
(Finishing Forum)
From contributor D:
I have a question about the flatting (flattening) agent. In decorative finishing, we use flatting oil. It's really only mineral spirits and boiled linseed oil, mixed in an 11:1 ratio. The purpose of this mixture is to keep the paint wet, like an extender.

In wood finishing, we use a flatting agent (gloss modifier) to adjust the sheen of a final finish. Why would a factory flat finish have a 20 - 40 sheen if there was additional flatting agent added? It seems like it may be the sealer used. If you were finishing with NC lacquer, why use a vinyl sealer instead of NC sanding sealer? Were you trying to add moisture resistance? I have found that I get an off sheen reading when I try the same schedule. All I do to correct the problem is scuff sand completely and re-spray. I make a special effort to completely knock down the gloss of the existing finish.

Another problem may be the method of application. I use airless equipment from time to time, but unless there is a fine finish setup on the gun, there may be an excessive amount of finish and sealers on the wood. You may have to wait a little longer for the chemicals to fully cure to get a true reading of the sheen level.

From contributor R:
To contributor S: Vinyl sealer is fine, just sand and shoot with a 5% sheen lacquer - make sure it’s stirred, and you shouldn’t have any problems.

From contributor C:
I have taken to spraying a couple of mist coats on top when I need a flat look. This gives me something like the matte surface on Formica. I usually do this with satin sheen product.

From the original questioner:
I am trying to figure out why I got the unexpected sheen. Even if the finish is full-filled (this one isn't), shouldn't the flatting agent still be at the surface to do its anti-reflective magic? The lacquer is about 27% solids by volume (including the added flatting). It was probably applied at 8 mils wet (painter with an airless). It just doesn't seem that applying it too thick would negate the effectiveness of the flatting agent.

From contributor J:
I would suggest that you do a cross-hatch adhesion test on the coating. I think your problems might be more extensive than you think.

From the original questioner:
To contributor J: There isn’t any stain – it’s lacquer, and it was all applied in 24 hours and it’s basically decorative (whatever protection you can expect from a lacquer system is ok). I just need to hit the dead flat natural look.

From contributor S:
Since no one has, I will ask the most obvious question. Did your guy stir up the entire flatting agent from the original product? I get that you added a quart and probably mixed that in, but I'm talking about the flatting agent that comes with the packaged product. Do you know this settles out and usually has to be dug off of the bottom of the can? When I open a new 5 of my 30 sheen finish, it takes me about 15 minutes to dig the flatting agent off the bottom and get it well dispersed.

The other thing is you of course have to check the product data sheet to know what the sheen rating is, since one manufacturer may call a 35 sheen flat, where another calls it satin. My manufacturer sells a dead flat that is 15 degree sheen. Their flat that I use is a 30 sheen, so at first I am not surprised you didn't get a 12 sheen from a product termed flat, but the fact you added more flatting agent and still ended up with 35-40 sheen doesn't add up. That's why I asked if your guy mixed this material right or maybe didn't take enough time to mix it.

Another thing, you mentioned spraying 8 mils wet, that seems really extreme. Do you mean two coats sprayed 4 mils wet? I would think 8 mils wet would be sagging like crazy. If the lacquer is a pre-cat, you are probably already at the maximum mil thickness. If you spray more, the finish is likely to crack.

From the original questioner:
To contributor S: There was nothing left on the bottom of the can. It was stirred up. It wasn’t a pre-cat, just lacquer. I'm guessing it was at the dry film thickness. I did find a few sags.

From contributor B:
Here are a couple of things to consider; the sheen can be off due to any or all of the following factors: The sheen measured on the closed pore and open pore wood will be different. Also, the sheen on black glass will be different then on wood. If you put on two heavy coats of 10 degree sheen, it will be shinier than one coat. The type of sealer used will also change the sheen.

I think you have one or more of the above going on with this job. Also a quart of flatting agent in a five gallon pail isn’t much. When you take a 20 gloss product and want to drop it to a 10 sheen, it will take way more flatting agent than it takes to drop a 40 sheen product to a 30 sheen.

From contributor F:
I would try filling your gun with lacquer thinner and shooting on a light, but wet coat - not enough to cause your finish to run or sag. When it dries, the sheen will be duller. The thinner will micro-pit the surface of the finish film, and this will result in a finish which is just as smooth as you see it now.

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