ROCKET KILN EXPERIMENT #1

 

My four pieces that were fired in my rocket kiln. I'm still painting my bisqued earthenware with acrylics. 

I want to be able to fire my ceramic efforts here, at home, and have no space for an electric kiln. I liked the idea of a rocket kiln -- less fuel, more heat, less time. It was an interesting experiment but not a raving success. I made a few mistakes, learning as I went and sometimes, sadly, after the fact. The temp inside my barrel kiln reached 1480F at its peak -- short of my goal of a sustained 1900F. I'll be trying to correct my mistakes and going another round with my rocket kiln soon. 

The heat riser was cast from vermiculite cement -- 4 parts vermiculite to one part cement. I got the idea from a video I watched about building rocket stoves. I later learned that concrete -- even vermiculite or pearlite concrete -- is not ideal for achieving the kind of temps that firing ceramics requires. However, I'm sticking with it for now, even in my rebuild. There is currently no budget for fire bricks. My chimney was a six inch vent pipe lined with one inch of ceramic wool. It left a five inch opening, so I had five inches all the way through.

Not the best image but more or less the configuration of my feeder box (9"x5"), burn tunnel(12"x5"), and heat riser(32"x5"). I mismeasured the length of my burn tunnel, which should have 17" long -- an important component and a sad mistake that may have been the biggest reason for my kiln's lackluster performance. 

I used a door designed for a camp stove and insulated my barrel kiln with two inches of ceramic wool. I thought that wool would contain the heat, but when my probe thermometer measured 1300F inside my kiln, the outside of my barrel measured 230F. My plan is to cover the barrel with fiberglass insulation to contain more of the heat.

My four pieces of greenware had been preheated in my kitchen oven up to 500F for almost an hour. All survived the attemp at firing and are ceramic as far as I can tell. Experts have told me that kiln shelves will produce a more even firing and even better temp results.

Rebuilding will mainly involve lengthening the burn tunnel to 17" and insulating the outside of my barrel.  I am working on more clay pieces, and will try again soon.