I draw on location, and unless on a plane, a train, or moving ship, I make oil sketches on location, too. Exigencies of painting on site: the challenge of weather, changing light, the possibility of never being able to return, enhance a necessity to be alert and of the moment.
As I try for directness, and luminosity, the studies are usually loosely painted. I like to work on a variety of surfaces and formats and usually carry linen, Denril and small pieces of aluminum cut in varying sizes and shapes. These form the basis for my larger paintings, often done on sheets of frosted Mylar, which is similar to the Denril but heavier. I keep a photo journal, which is useful for recalling the impact of a place and things that may have colored the experience. The photos also provide information, like the structure of an ice formation or a rock fall, which might not have been quite fleshed out in the sketch. My subject is usually larger than what can be seen without turning, and I am gathering in image/comprehension bits which take place in time.