Everything posted by MikeSible
Hi, I'm looking for help with my kiln design. I am having trouble getting it to temperature most of the time. It is ceramic fiber, cylindrical, approximately 50 c.f. and propane fueled with a 500 gal tank. I don't have the exact btu available, but I believe it is more than enough, with a single burner. I primarily fire it with a saggar, which is made of hard brick, also cylindical, that sits and fits exactly on a 26" round shelf. The fire box is about 4 inches tall, made of soft brick, which supports the fiber shell. The gap between the bottom shelf and the wall varies between 3 and 4 inches while the gap between the saggar wall and shell is about 3.5 inches. The gap between the top of the saggar and the roof can vary from between 3 and 7 inches, with little difference noted in performance. It generally peaks out at about 1800 deg., however when it windy, I can get it up to 2200+ without any trouble, so obviously there is an air flow issue. I have experimented with innumerable combinations of vent and intake size, including a flue, although most of the time I haven't had a flue. It seems once I get the vent large enough, I just start losing heat. Is my only solution a blower? My other thought is to rebuild the roof so that it is more of an arch. Any help is very much appreciated. Thanks.
Thanks to everyone for your help on this. I'm not actually looking to get to cone 10, I was just illustrating that I have enough in the BTU dept. to get to there on a windy day. I'd be happy with cone 06, probably. 04 hopefully, just a hard bisque. But, I will add some fiber, bulk up and increase the fire box size, and try a chimney again. Thanks again!
Sorry, all. Turns out whiskey + math is not a good equation. The kiln is 36" tall, so the cubic feet is roughly 18. Math = (3.14 * 16.5^2 * 36) / 12^3 . The burner is the MR100 venturi I purchased from Ward Burner Systems after consulting with them. The fiber is 2" of 6lb. and 1" of 8lb. It is an updraft kiln, with a flue. I was using the term flue when I should have said chimney. So, I tried a chimney at one point, but generally don't have one. I believe the specs I found suggested a port size of 1 1/2 times the size of the burner and the flue I started with was approximately 4-5 inches by 4-5 inches, but I ended up making it slightly larger and then adjusting the size during firing by draping pieces of fiber over the edges to cut down the size. When firing, I start with the burner inside the firebox during the candling and gradually move the burner to the outside of the kiln to about an inch away. Like I said, I've experimented a lot with the flue and port sizes, but with little effect. I've tried adding a separate port just for extra air as well. Also, the kiln is in two parts, so I can fire using just the top half, which is probably about 10 c.f., which also doesn't seem to affect the overall temp capabilities. Thanks for your quick responses .