Week three of plein air Bronxville brought nice weather,amazing because it has been raining for days.This was a 15 minute demonstration i made showing the class the importance of blocking an image in as quickly as possible. I read that with in your first ten minutes of painting alla prima your image should look all filled in with most of the hard problems figured out. This is tough to do and with practice it will come, i would continue to work this sketch up for another 2 or 3 hours before finishing.