What we did

The PrattMWP anagama

The firing went very well until the end. Before getting into the schedule a few notes are needed. More images will be posted soon...

1) We changed the door configuration. All ports were brought up one course. We (I) thought this might help with keeping coals in the firebox while letting more primary air in over the coals. The secondary air ports were move up as was the stoking port. These changes proved to be a problem in hindsight. It created a jet stream through the chamber making damper management more difficult and heat distribution erratic. At least that is my thinking.

2) The ware load was not suited to the chamber. Too much flatware with not enough volumetric ware to baffle the flame. 

So, to condense the schedule (Our pyrometer is in the rear of the chamber; the cones in the rear are 8,9,10, while in the front we use 8,9,10,11,12. We have easily reached ∆ 12 in the front in past firings.)-

Start up: 6:30 pm (Thursday April 26)

Our intent was to go up very slow. We had a piece in the front that was tall and did not want to risk it. 10 to 15 degrees every half hour. We (Amber and Eric) stoked lightly through the night to hit our morning temperature goal of 500˚ F.

From that point we kept the ramp the same, keeping the damper 3/4 open for the duration. By midnight Saturday (April 27) we were at 1500˚ F. 

My take on a long firing is simple- get it up to temperature and then soak for as long as personal energy and fuel allow.  Here we took too much time at the front end to protect the ware.  It is in some ways a waste of fuel. But the up side is that my sophomores got some experience in careful, attentive stoking, a process they will surely remember for future firings. 

We hit 2000˚ at 10:30 am on Saturday. Our ramp was fairly consistent for the rest of the firing.

At 4:00 pm Saturday we had ∆ 8 soft in the rear and ∆ 10 down in the front.  Then came the big stall. No matter what we could not push heat to the rear. We had the usual positive cues such as good heat in the firebox as indicated by lots of blue flame off the coals and white heat just above the coals, but we began to notice the flame as flat and streaking through the chamber.  Also, we noticed a lot of unburned fuel or carbon at the crown of the firebox and into the upper ware chamber.

Previous door setup.

I think the problem was the raised door ports. We were getting less chamber time from the flame, a jet stream in a sense, with the unburned fuel causing the stall. We had created zones in the firing chamber. I can't be sure, but when trying to dampen the kiln, we could not get the right fuel to air ratio, or I should say, get the flame to work around the chamber, not through it. Lots of smoke under the shed, but little to show for it in the kiln.

Door and stoking port block.

Exhausted, we called it quits around 5:30 pm Saturday (April 28). Although we got some great pots from the kiln, learning to fire this baby is a work in progress. 

As I said before, I have made some changes to the kiln floor and stacking scheme. I will certainly go back to the door pattern we used earlier. The changes and strategy will be discussed next post.

Wood fired by Bryan McGrath