I fired my kiln, Big Anthony, for the second time this weekend. The first firing taught me an awful lot - and you folks, more, here. (Well, many other threads, but that was the latest.) This time was pretty well a failure. I messed up the reduction (again), I screwed up the soda (again - worse than last time). But I did succeed in not crash-cooling! Woo for me!
I'm certain all the problems I'm having are 1. My fault and 2. Obvious issues. The sort that, when identified, will make you throw your hands in the air and say, "MY GAWD! How stupid can she be? Yes, you have to close the lid!" or something equally as neophyte. If I could have someone knowledgeable on-site, for maybe an hour or two of the firing, I'm certain all questions would be answered. However, not having that option, I'm here to bug the heck out of you guys instead.
- With my former little kiln, I could put it into reduction by moving the damper. With just an 1/8" move, I could make it smoke, or shoot out a 4" flame, or nothing. I labelled these options "bad, reduction, and neutral."
It is not so easy with this bigger kiln. Now I either get 1. Gobs of black smoke (damper pretty well closed); 2. Nothing (damper open 1"); or 3. Rapidly decreasing temps (damper open more than 1"). I can't find that "short flame shooting out" place. This all assumes I'm firing with gas only.
- The damper has to be closed down to only 1" open in order to increase temps. Open more than that, it won't go up.
- It stalls out at 1900°F. I use wood after this, and when I do, I don't do it right. Wood creates massive fires coming out of peeps when opened, accompanied by gobs of black smoke. Each time I add wood (about every 10 minutes at 1900°, closer together at the end) I open the damper up to 3", to try to avoid this effect, while watching the temp drop rapidly. Over a 3-4 minute period, I slowly close the damper back down to 1" as the smoke lessens. Once it gets back to 1", the temp rises again.
- Many pieces are cracked - either where I attached handles, or where there was a paper-thin crevice (I have a nick on a rib I use on the outside of pots - it leaves the tiniest groove. This groove grows in the kiln and in some cases cracks.), or in the foot.
- I don't think I'm using the burners properly. They just don't sound right. They sound loud and dirty and orange. I've messed an awful lot with the primary air thingies, and it doesn't do much. (I took a video; I'll see if I can find it.)
It's a low-pressure system. The dials go up to 10 PSI, but when both are burning, they max out at 5 PSI. They're MR100s, running together on two 100-lb tanks. The wind was strong this weekend, and when it really gusted, it made brief back-burning noises.
- It fires very uneven - at least two cones difference from top shelf to bottom shelf, probably much more. There are only two shelves, and I put a third, empty, shelf atop all of it, in hopes of keeping the fiber roof from falling on the pots.
Okay. So here are the facts about the kiln and the firing:
- I followed two of your recommendations this time. 1. I put a half brick in the flue and 2. I covered the hole above the damper with two pieces of kiln shelf:
- I'm still single-firing, but to save me from a tiring 24-hour firing, and upon the recommendation of Marc Ward, I fired slowly (9 hours) through 1100°F the first day, shut it up tight and slept. Then, on Day 2, I fired quickly (8 hours) to Cone 6 (it was 200°F when I began on Day 2).
- When peering into the kiln, I can see the the majority of the flames are going right under the bottom shelf, directly out the flue. The bag wall is 5" high, but the bottom shelf is a bit higher. I'd say about 1/4 or less of the flames go above the first shelf, and none of them reach the second shelf. Hopefully you can see what I mean in this photo about the height of bag wall vs. shelf. I figure I need to make that higher than the bottom of the first shelf?
[Split into two posts to accommodate all the photos.]