Overspray and Bounce-back

Old high-pressure spray guns like this Binks #7 gun create a lot of bounce-back.

Terminology is important. If we aren’t all using the same definitions, we can’t communicate. Using sloppy language is one of my pet peeves, and I spend lots of effort just defining terms. Here’s a term I often hear misused: overspray.

Overspray is the sprayed finish that misses the target. It’s less common on large targets such as tabletops or cabinet doors, but it’s very common on narrow targets such as chair rungs and spindles. (The way to reduce overspray on narrow targets is to reduce the width of your spray pattern.)

Where the sloppy language occurs is the use of the term “overspray” to describe bounce-back. Bounce-back is the finish that hits the target and bounces back off of it. Both overspray and bounce-back are waste and should be exhausted with an adequate exhaust system.

Bounce-back is worse with old high-pressure spray guns. It can be reduced significantly with the softer spray produced by HVLP spray guns. HVLP stands for high-volume, low pressure. Almost all spray guns sold today are HVLP, primarily because they produce less waste and fewer problems.

HVLP spray guns, especially those powered by a turbine, produce much less bounce-back.

The air source for HVLP, whether turbine or compressor, isn’t that significant, though in my experience, turbine-supplied spray guns have a softer spray and thus less bounce-back than compressor-supplied guns. Still, there’s some bounce-back.

– Bob Flexner

Flexner on Finishing
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