Black Work For Fingers stretch a canvass that is 10 feet wide and 15 feet tall paint the canvass dark gray [ 25 percent white/75 percent black ] crush three pounds of black coal until it is a fine powder mix the powdered coal with as much clear gel medium as it takes to make the entire mixture wet quickly coat the canvass with the coal and gel medium mixture with as thick of a layer as you possibly can without letting it dry wait 60 minutes set a timer for 20 minutes using nothing but your fingers scrape as much of the material as you can use nothing but downward motions, and start at the top of the work stop after the 20 minutes is up allow to dry for three days frame in a dark wood frame