When you are painting at high altitudes or in extremely hot dry conditions, you can modify acrylics by using glazing medium instead of water, allowing them to stay moist long enough to at least get your brush to the canvas before the paint dries.
But what do you do in cold snowy conditions?
Unlike oils which are naturally tacky, acrylic paints are somewhat moist to begin with. Acrylics depend on evaporation to dry, and there is no evaporation in extremely cold temperatures. The air simply won’t hold the moisture it can at higher temperatures.*
A few years ago I was painting for a big museum exhibition with a bunch of friends, all oil painters. We had painted together in Big Sur, in St. Louis, and in New York City.
We arrived in Yosemite in early February one evening during a big snowstorm. The next morning we all bundled up and raced out to paint. All the oil painters were turning out beautiful one-hour sketches. I, on the other hand, was weeping into my paint box as the paint dripped off my canvas.
Acrylics simply will not dry in below-freezing temperatures and you’ll wind up with a creamy mess. One painted area blends messily into another as you try to refine shapes. There is no tack whatever, and unlike watercolor the canvas doesn’t absorb anything.
Some of possible solutions to this problem, other than substituting oils for acrylics:
If it’s a sunny day, you’re in luck because you can angle your canvas toward the sun and that will help dry the paint.
Or try working on several paintings at once, slipping each face-up into your car and letting it dry while you work on another canvas.
Still better, if you’re painting near home, you can rotate paintings into the house to dry. (A hair dryer would allow you to run indoors and dry the very painting you’re working on, so you can keep your focus on one canvas at a time.)
The best solution: stand in the window and look out!
Caveat: don’t keep drying paintings in rooms you live in for any length of time or on an on-going basis.
Even when they appear dry to the touch, they are still off-gassing and prolonged breathing of the fumes is bad for you.
My friend John Cosby nearly died from breathing the fumes of acrylic paints he used in an airbrush. Only having a doctor friend who picked up on his problem allowed him to realize what was causing his illness before it was too late.
When he gave up illustration and took up plein air painting, he changed his medium to oil.
* See the section regarding drying times at Golden Paint’s website: http://www.goldenpaints.com/technicaldata/drying.php