I have been wanting to spray shellac and SW Sher-wood Kem Aqua Plus clear for a week but the weather has been hot.  Now the temps have dropped some but the humidity has gone up.  The SW product best dries at 50% RH or lower and 77 deg or higher.  I have been waiting for a window where the temps are below 80 deg and the RH below 80%.  I do all of my spraying in the garage which does not have A/C.  Am I taking too big of a risk if I spray with the temp and RH above 80?   Danl

I spray all my stuff out side in the shade even if its 100 but I only use lacquer...Very high humidity will turn clear lacquer cloudy on certain days. Those 12 days of Christmas was sprayed with lacquer.

Kem Aqua is a water-borne finish.  While maybe called a "lacquer" it is not the traditional nitrocellulose lacquer.   Traditional lacquers will blush.   For a while, one of my customers overflowed their warehouse and I had to do all the touch up work in a rented semi-trailer.  I spent most of my time removing blush as I went along.

 

W/B finishes cure in two stages,  first the water evaporates, then the glycol ethers evaporate as the resins coalesce.  So my guess is that it will slow down the water evaporating.  Air movement might help.

 

I do know one critical factor with w/b finishes is the low-end temp.  Most of them don't work / cure well below about 65 degrees.

I plan to move the spray pieces into the kitchen right after they are sprayed to allow for controlled evaporation.  I was mostly concerned that the shellac & finish would dry before it hit the wood because the air entering the gun would be dry air, the structure would be of ambient temp, and perhaps the pieces would take on a foggy appearance due to the humidity.  Danl

For the shellac, a trick that might help (I've never done this) is to add a teaspoon of turpentine to the finish before spraying....it's often claimed to slow down the alcohol evaporation.