One of my goals for 2013 is to do business more effectively, and more efficiently, in terms of time and money. Toward that end, I've been trying to make my firngs faster and more efficient. As part of the latter, I needed to figure out the current BTU needs of my kiln.
This is not something I've spent a lot of time thinking about, which makes me a typical potter idiot, just cluelessly happy-assholing around, using whatever burners come to hand, according to Marc Ward of Ward Burner System. Okay, Marc didn't say that, but I feel it was implied. Or else I am projecting - could be that, too.
Kiln material, size, and firing temperature all contribute to BTU requirements. (Backing up just a teensy bit: BTU stands for British Thermal Unit, one of which is the amount of energy needed to heat one pound of water by one degree Fahrenheit.) Hard brick kilns will require more energy than soft brick kilns to reach a given temperature for the simple reason that they are less well insulated and lose more heat through the walls. Larger kilns will require more energy because duh. A hard brick kiln will need 16,000 - 20,000 BTUs per cubic foot, to reach ^10; a soft brick kiln will need 10,000 to 16,000. Since mine is half-n-half - hard brick interior, soft brick exterior - let's thread the middle ground and say I need 16,000 BTUs per cubic foot to reach ^10.
So, now I need to know how many cubic feet in there; not stacking space, but the whole enchilada. What would be a simple equation - width x depth x height - is comlicated by the arch. How to figure that?
The equation looks like this: Width x depth x wall height + (2/3 x arch rise) For me this comes to just under 32 cubic feet. 32 x 16000 = 512000 BTU to reach ^10.