When we originally built our kiln in 2000, we used all recycled brick and built it around the size of shelves we already had. It was a flat top, built mainly of stacked arch brick for the walls and a fiber (ceramic blanket) and heavy sheet metal roof. Not fancy, but we had a kiln and didn’t have to spend much money to put it all together.
It took at least 7 years of painstaking tweaking and firing before I really got to know its ways. About 5 years ago a dog we had knocked over the entire stack of old brick we were using for the kiln door, breaking most of them!! (..sigh) Long story short, it has been a struggle from the get-go to achieve reduction with any reliability, if at all.
As I think I mentioned in my last post, the old kiln as it was is no more. The flat roof – gone. The danger of fiber bits falling down into pots if you accidentally brushed the roof of the kiln with your head when stacking/loading – gone. The flat top was replaced with a retrofitted sprung arch and we finally were able to get new brick for the door. Extra fiber and roofing tin wraps the outer walls now as well.
The other exciting change made was replacing the old severely warped cordite shelves in favor of 6 new nitride bonded silicon carbide shelves. As you can see in the pictures, some of the old shelves were warped an inch and a half to two inches in places (I put one of the new nitride bonded shelves beside the stack of old shelves to show the difference in thickness and flatness). As with a wood or soda fire, loading typically involved painstakingly “wadding” each and every pot for the firing with a mix of 60/40 china clay to alumina hydrate. It was the only solution I could see to prevent warping. I have several potter friends who have those zoomy Advancer shelves that run about $100 a shelf in the size I was looking at. The nitride bonded are a step down from the Advancers, but are a lot less cost prohibitive, costing maybe $20 or so dollars more than a comparably sized cordite shelf.
These new nitride bonded shelves weigh all of 11 pounds (the old cordite shelves in comparison weighed 44 pounds!), so loading the kiln takes a lot less of a physical toll on me and I can load it independently. I still do wad some – little teeny wads – (vs using kiln wash or sprinkling alumina hydrate on the shelves), especially on those clay bodies I might be firing that might be a bit tighter than our native clay to prevent sticking, Loading takes a fraction of the time as does the preparation of the wadding itself. Now that I have flat shelves, the wads can be glued on in advance as well.
The new arch in combination with the new flat shelves gives me at least, I am guessing an extra foot of stacking space. Not only that but the kiln now reduces and fires more efficiently using about a third less propane per firing. With the rising price of propane ($264 for 75 gallons this last delivery), the upgrades to the kiln and shelves couldn’t have come at any better time. (Better for the environment as well.)
As an aside, we got our new shelves and brick from Larkin Refractory Solutions in Atlanta. Wonderful customer service and knowledgeable staff.