I've been giving my paintings six months drying time. But I realized that a painting I complete now will not have the benefit of my local high July/August temperatures to cure.
I could wait a year instead, that would guarantee each painting gets the warm weather to speed drying. But simply waiting for a length of time is not scientific, because we are all in different seasons and climates, and the materials are different in most cases. That makes any time-based drying guidelines mere guesswork.
Is there a way to determine whether a painting is dry enough to varnish? I know the fingernail test, but that only works for thick paint.