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.
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.
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.
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.