As mentioned, manufacturers aren’t very informative about the sheen of the products they sell us. First, their terminology is vague. (Among themselves, they use a more exact numbering system from 1 to 100, with 100 being perfect gloss; but they rarely share this information with us.) Second, they often give us only two choices.
What if you want a sheen that is flatter than anything offered in the store, or you want a sheen that is in between the two choices offered?
To create a flatter sheen, let the flatting agent settle to the bottom of the can (tell the paint clerk not to shake the can). Then pour off some of the gloss finish at the top into a second container. You will then have some gloss in one container and some flat in another. Blend these two until you get the sheen you want.
Of course, you’ll need to experiment by applying some of your blend to wood to see the sheen you are creating. Be sure to apply two coats because it’s only the second coat that will produce an accurate sheen. It doesn’t matter, of course, what you use for the first coat.
It’s even easier if you want a sheen in between those of two products offered. Simply stir the flatting agent to put it into suspension and then mix the two.
Once you have determined the sheen you want and have a product that will produce it, problems are rare. The most common is not keeping the finish stirred. More rare, but also possible, is white specks appearing in the dried finish film.
It’s not necessary to continually stir a flatted finish while brushing or spraying. But it is necessary to stir between coats.
If you are brushing, some of the flatting agent will have settled and the finish you are pulling off the upper level of the container will be glossier than you intend. If you are spraying, some of the flatting agent will have settled and the finish entering from the lower part of the spray-gun cup will be flatter than you intend.
Though it is rare, you may find tiny white specks in your dried finish and wonder where they came from. Unless you are using a dirty finish, it’s most likely you have broken some clumps of dried silica away from the lip of the container. These clumps don’t break up in the finish so they show up as white specks in the film.
There’s no way to effectively strain these clumps because they are very small. It’s best to toss the container and all the finish in it and begin again from a fresh can. You’ll have to sand out the white specks from the dried film to remove them. PW
Bob is the author of “Understanding Wood Finishing” and a contributing editor to Popular Woodworking.