I came across this great blog article about plein air painting through Jerry's Artarama.... sounds like there may be several posts on the subject. Plein Air Painting - An Introduction
The term en plein air is simply French for "in the open air," meaning plein air painting is just creating art outdoors. Now, you'll be thinking, "What about cavemen? What about Australian aborigines? What about all those outdoor megaliths and Egyptian statues and everything that's been around for thousands of years before France even existed? Surely THEY didn't work en plein air!" Okay, technically that's correct. It's just that the French coined the phrase for it back in the 1800's when painting outdoors really took off and its popularity skyrocketed.
Read the rest of the article by clicking on the link below...