Wednesday, June 15, 2011

Beautiful Bisque!

First test load!
I think I just wet my pants. I finally fired my kiln for the first time. I'm such a wuss. Get a new used kiln with no instruction manual and spend weeks fretting that everything is not right and that somehow, you will screw it up and all your pots will explode, I say EXPLODE!  But alas, they didn't. My biggest problem? Not finding a manual or someone else with this kind of kiln. Cress makes similar newer models but oy vey, the instructions leave much to be desired. Horribly written.

So here's the deal for any old Cress kiln users with a KilnSitter [tm] that say "TurboFire" and have a thumbwheel and side dial on them, the dial on the side can be set to manual or one of several automatic firing schedules, "A" being the fastest firing with a fast ramp in speed; the letters following indicate slower firing speeds. Or you can set it to "Off/Manual" and fire it manually by using the thumbwheel on top to increase the power and ramp the heating. When you set the dial on the side to a letter, the thumbwheel moves automatically depending on the schedule you choose. When you set it to "Off/Manual," you move the thumbwheel yourself. I read someone's comment that these old Cress kilns with the thumbwheels act like digital programs on new kilns but it's an analog device.

So here's what I did with the first test bisque load. I put in a small cone 07 cone in the KilnSitter and the timer on the maximum hours since I knew I would be monitoring this firing closely. I set the thumbwheel to the "/ \" position and the dial on the side to "Off/Manual." I cracked the lid a couple of inches and unplugged the top peephole. Initially, I left the side dial on "Off/Manual" and moved the thumbwheel to "1" and let the kiln click on and off for about an hour, then realized I'd forgotten to engage the thumbwheel button. No problem as it wasn't on an automatic program anyway and I think that's what the button does, engage the thumbwheel to coordinate with the side dial setting. After about another half hour when I felt comfortable that the temp had reached over 212°F, I set the side dial to "E" my slowest setting, depressed the thumbwheel button, lowered the kiln top completely and let the kiln do it's thing for another hour. Once I reached some low color (can't remember how long), I set the side dial to "C," a middle setting and let the kiln ride until it reached temp. I probably could have set it to "A," it's fastest once it reached color for a bisque firing but since it was my first one with this kiln, I went for the middle of the road. The estimated time on the KilnSitter was about 6 hours. I plugged the peephole after it shut off, turned the thumbwheel back to the "/ \" position and let it sit until this morning.

Everything came out just fine. I did not have a witness cone set-up in the kiln but I may do that in the first glaze firing. I still have quite a bit of greenware left to bisque and will probably get to that first. The glaze firing will be a more anxious time for me but it would be anyway because glazing is always where my best laid plans break down. No doubt I will be ready for a cone 6 glaze firing when the temps outside get back into the humid 90°'s.


  1. What about any instructions for an even older Cress C-14 kiln with everything manual and 3 separate switches for the 3 pairs of heating elements?

    1. Sorry for the long delay in replying. You could contact Cress via email and see if there are any old instructions for that model available. Having said that, I have used a completely manual kiln at college, three zones, three dials. We were instructed to start with all dials on low for several hours or if dealing with large or thick pieces, low on the bottom for an hour and then add the other two on low after an hour. We either kept the dials on low until color appeared (we fired overnight in the kiln room) and then pushed the top and bottom to medium for an hour then added the middle zone after another hour, or if we felt everything was fairly consistently dried and similar density, pushed all three zones to medium for two to three, sometimes four hours, followed by the switch to high until the cones dropped. Our large oval manual kiln at school had a kiln sitter that would trip but we had spy holes and witness cones as well. The general rule of thumb for bisque was/is slow, slow slow but once you pass quartz inversion (you see color), you can turn the temp up fairly rapidly. I still like to go slow to burn out as much organic chemistry as possible. Keep an eye on making sure your pieces are definitely dry before you put them in. If you have thick pieces, fire as if you're crawling until you see color then you can go a little faster but still, take it easy.