Yes, You Can Have Too Much Ventilation
Earlier this year I decided to set up a spray booth in my shop so I could spray finishes on crappy days. It did not turn out well.
Usually I spray outside, so I have to wait for a pleasant day with the right humidity, no pollen, low bug count, no rain and etc. Sometimes the weather does not cooperate, so a makeshift spray booth seemed just the thing. So I bought tarps, filters and an industrial fan to ventilate things.
It seemed to be working really well. I wear a respirator when spraying, and when I’d remove my respirator when using the spray booth I was surprised how little solvent smell was in the air.
I was well-pleased.
My finishes, however, were not.
The fan moved so much air that my film finishes would become rough to the touch because of all the turbulence. It was similar to what happens when you spray too close to the work or spray over a wet spot two or three times by accident.
At first I thought I had the settings wrong on my gun. I did not. Then I thought I had the wrong needle size. Nope. Perhaps my turbine was losing power and couldn’t atomize the finish? Nein. My finish was old? Someone had put a handful of sand in the finish?
It was the air flow. Too much. Way too much.
I put the fan in the shed for now and have returned to spraying outside on suitable days. Maybe I’ll try again with a smaller fan, different filters or a different configuration. Or not.
— Christopher Schwarz