Svend fired the smaller kiln a couple of weeks ago. The crew were Svend, Harriet and Brigitte.
Svend had finished packing on Friday at midday and the gas on very low when Brigitte arrived at 1.15pm. The firing would last until Monday around 3:30pm.
A rough walk through the firing stages.
Svend was on the 6 to 10 shift, Harriet would do the 10 to 2 and Brigitte the 2 to 6. Brigitte and Svend had a bit of banter over which shift they would do as they both prefer the graveyard shift. Brigitte got to do the graveyard shift and Svend got to go for his swim everyday so everybody was happy. Team work !
An hour after the firing had started, Brigitte therefore came on shift; the gas worked by itself so her job was to move wood from the outside of the kiln-shed to the inside as it was raining badly, and also to get some hard wood ready for when Svend came on to change from gas to wood. Below are Brigitte’s two neat woodpiles in front of Svend perfect ones !
When Svend came on at 6pm, he continued firing with both gas and hard wood, and he changed over to just wood at 7pm. From then on, all members of the team worked solo. The task was to get a slow climb to reduction and then heat work with constant reduction until midday the following Monday. On Monday, all members of the team worked together to get all cone 12 down all over the kiln.
During the main part of the firing, we were stoking from the front and from the stoke holes at the fire mouth; there were two biggish pots in the firing chamber against the kiln walls that required a lot of ash, hence the side stoking. Svend was also side stoking the middle and the back of the kiln during his shift in order to even out the temperature and to get ash towards the back of the kiln. At the end of his stokes, Svend was throwing water through the front. See the videos below to see what I mean.
There are three theoretical reasons for throwing water in the kiln during reduction: firstly, when cold water comes into contact with the heat, it creates steam and a sort of explosion that lifts the ash and throws it everywhere in the kiln. Secondly, it supposedly intensifies the reduction. And thirdly, it clears out the smoke in the kiln. However, this is very dangerous, people could get scolded by heat and steam, therefore only Svend is allowed to do it.
At 4am Sunday morning, Brigitte reported that cone 9 was starting at the front and when she came back at 2pm the same day, it was completely down; cone 10 was pointing an hour later. By the end of her shift at 6pm, cone 9 was down on the right hand side, beginning on the left hand side and cones 10 and 11 were starting at the front. Throughout the main part of the firing, the right hand side of the kiln was hotter, but strangely, at the end of the firing, when the team was working together, the left hand side got hotter.
Below is a photo of the chart for more detail.
At midday on Monday, the team worked at getting cone 12 down at the front. By 2.30pm, the front was done, so they proceeded to the sides, throwing 3 sticks in each side and checking the chimney for smoke. When the cones were stubborn in one stoke hole, they worked on the next one to get a good advance there, then they would come back to the stubborn stoke hole until cone 12 was down. All cones were finally down by 3.30pm which meant the end of the firing so it was time to clam up the door at the front and to put the pyrometer away. Svend worked out that we used 3 cords of wood.
A few notes on some of the kiln’s features.
On Svend’s kilns, the side stoke holes are positioned half-way between the floor and the top of the kiln. This means that the stoke holes act like a passive damper and suck air through the kiln and prevent flames from lashing out of the kiln. If the stoke holes were positioned higher, they would act as a chimney and this would result in big flames and danger for the stokers.
Svend has built some passive dampers at the back of the kiln; they are used to minimise black smoke and to avoid upsetting the neighbours. When we use the passive dampers, the main damper at the chimney stays open. Below are pictures of the main chimney damper and of the passive dampers. In the picture of the passive damper, you can see a dark patch surrounded by orange flames: it is the cold air that gets in and that gets surrounded by the heat. The mixture of hot and cold air creates vortexes or turbulences that fight each other.
The flames escape through the chimney via a small arch (pictured below with the plywood still in place). When he packs for the next firing, Svend is thinking of building a wall of pots in front of the first arch in the picture, which separates the main kiln chamber from the tube that leads to the chimney so that the heat does not escape to fast. The tube gets really hot and pots that got fired in this tube in the last firing were badly dunted.