Even though it looks like a hobo party, its really quite organized.  The barrel in the background is carefully loaded with sawdust, straw, copper filings, clay pots, and wood.  It gets lit and then is allowed to burn down.  The white "caveman R2-unit" in the center is our portable, lightweight Raku kiln.  Soft fire bricks make a wood-burning chamber atop a cinderblock base.  High temp (up to 2400 degrees F.) batting and wire mesh make the kiln body and a modified steel bucket provides draft.  There is a peep hole to check for glaze melt.
When the glaze does melt, its time to remove the upper portion of the kiln.  The glaze melts at around 1400 degrees, so lifting that kiln can be harrowing.  High temp gloves and tongs allow me to move the hot pots into various combustible piles (in the trash cans).  The heat from the pots causes the combustibles to combust.  Fire lives on oxygen, and we let it burn for a little while.  We then choke the fire by covering the cans.  This starves the fire of oxygen.  The fire uses all the remaining oxygen including what's inside the clay of the pots.  When the oxygen is ripped out of the clay, it is replaced by smokey carbon effects.  The random effects that happen in those 20 seconds of reduced oxygen are the point of the whole process.  That and the campfire smell.
See more artwork from Jason Jaspersen at jjjaspersen.com, and on social networks such as Facebook, Twitter, and LinkedIn.