In a recent blog, I spoke briefly about the two Vs in wood lacquer. Now it’s time for the rest of that story!
Every coating has two things in it; volatiles and volume solids. Those are the two Vs. In chemistry, a volatile is a substance that has a tendency to vaporize or evaporate. Coatings contain Volatile Organic Compounds, or VOCs.
The environmental trend is to get these to be as low a portion of the coating as possible. Some coatings are approaching zero VOCs. But VOCs are still around to some degree in most coatings. VOCs are another chapter all together. Let’s not go beyond here for today.
Volume solids are the visible remainder of a coating and one that those in my line of work tend to talk a lot about. Volume solids are those resins and materials that remain after the evaporation process ends. They are the film-forming compounds. The higher the percentage of volume solids, the quicker you can build a film.
As an example, the good old-time nitrocellulose lacquers are fairly limited in volume solids. They might get as high as 21% but, by and large, they are in the teens. Conversion varnishes, by contrast, can be up into the 30s and 40s. There are other kinds of coatings that are even higher than this.
Then too, pigmented coatings will always be higher in solids than the same formulation in clear because of the pigments. Since pigments don’t themselves evaporate or have much in them that does, they are a part of the volume solids. Also, a dull-sheen product will always be higher in volume solids than the same product in gloss. Like pigments, the flatting paste is a part of the volume solids. It remains after all the evaporation is complete.
Don’t be confused here. We’re talking about volume solids and not weight solids. The weight solids for a given coating are always higher than the volume solids. Think of the difference this way. Volume solids refer to how much space the coating takes up. Weight solids are about how much the elements in a coating weigh.
These are the keys to calculating how much coating your need to reach a certain thickness. We'll cover that in the next installment.
Until next time…spray on!
Bernie Bottens writes and teaches on the subject of wood finishing in industrial woodworking. Based in Vancouver, WA, he teaches wood finishing to shop owners, shop foremen, spray technicians and finishers all over the Pacific Northwest. Bernie is the owner of Kapellmeister Enterprises Inc. He can be reached at [email protected].
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