We are now into the dog days of summer when the humidity is very high, not to mention the temperature. It is under these circumstances in particular that finishing can become a sticky mess, unless you are lucky enough to have an air-conditioned shop space. Although it's best to avoid finishing if the relative humidity is over 85 - 90%, there are a few tricks that can help you if you absolutely have to apply a finish when it's like a sauna in your shop.
I began my adventures in woodworking and wood finishing here in Atlanta over 25 years ago, in a very small, one-car garage with no air conditioning and to say the least, a very tight finishing area. Not having the luxury of spray equipment and a spray booth, I had to rely on hand-applied finishes such as oil-based varnish, shellac and brush lacquer, which all tended to dry much slower in the very stagnant, hot and humid environment. At the time I thought that the heat would be more than enough to dry any finish, but I noticed it seemed to take forever.
Blowin' In The Wind
Because of my frustrating drying problems, I asked a friend who had a shop close by for advice. After listening to my complaints he suggested placing a box fan several feet away from the pieces being finished, turned on to low, blowing away from the work and drawing the air over and away. "That should do the trick," he told me, "since air movement is the most important aspect when working with most finishing materials."
Sure enough, he was right and in a later conversation he politely pointed out that in the instructions on the can it said the product should be used "in a well ventilated area". Of course, I had thought that meant because of the fumes. Sure wish those folks who write those instructions would be just a little more forthcoming with the info!
Most finishing products cure best in temperatures ranging from 65°F - 80°F and a relative humidity of 50% or less. In higher humidity environments, in addition to good air circulation, additives such as Japan Drier will improve flow and drying time, and using a dehumidifier can also help control the moisture in the air.