A New Gas Kiln

Comming soon the Plans!!!

By Leonard Smith

After some 300 firings our original Fibre lined gas kiln was beginning to show signs that its working life was coming to an end (large holes would appear during firings) so it was time to make decisions about a new kiln. Designing a new kiln involves asking yourself a series of questions and by answering these questions the nature of the kiln is determined and ultimately, so is the nature of the work that comes out of it. The major questions that Lindy and I asked centered around the type of glaze results we wanted from our new kiln. As we fired to stoneware (around cone 10 Orton) in reduction and we required that it also be capable of slow bisq., firings, we decided to use LPGas our source of fuel. Four small burners rather than two large ones were chosen to give control over slow firing and to ensure even heat distribution in the kiln. Lindy was determined that she to get similar results to an old brick LPG kiln that we used to fire student work in at Hornsby Tech. I have always seen the conservation of fuel as a primary need for a kiln so it was decided to build a kiln lined with Refractory Insulating (RI) bricks and backed up with fibre. This ensured slow cooling and good fuel efficiency.

By consulting Steve Harrison's refravtory wall composition tables in "The Handbook for Australian Potters" we were able to work out that this represented the best compromise between heat storage and economy. With the concerns about fibre and health this also represented an attractive proposition with the fibre keep safely behind the bricks. We both wanted a kiln with a swinging door, having spent much too much time bricking up wickets to use that system for the door and we decided that as this would swing out of the way when we were loading or unpacking we could make this completely of Ceramic Fibre. We also ensured that whenever we handled or were near Ceramic Fibre that we wore a suitable dust mask.

The next important decision focused on the size. Too small a kiln and you soon regret all the time spent firing small loads; Too big and you never fire often enough to learn enough about your kiln and your glazes. Previously our kiln was 8 cu ft and we settled on a kiln about twice that size. A this point we chose to use 600 mm x 300 mm (18 in x 12 in) kiln shelves as we already had a stock of these. So on a piece of graph paper Lindy laid out the shelves and allowed for the burner placement and gas flow around them. With these dimensions she was able to expand them to the nearest brick size so as to eliminate unnecessary cutting. From here we decided the height we wanted to get the right volume and set up the ergonomics for packing. The floor height was set at a comfortable level and then the arch design and height decided. So this finalised the basic design.

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We sent our plans to Steve Harrison of Hot and Sticky, who organised the design and welding of the frame. This is an angle iron and weldmesh construction that meets the need for strength and lightness so that the kiln can be transported easily. The frame was delivered and we set about building the kiln.

Firstly the floor was laid in dry and then heavy duty aluminium foil was used as the outside lining. We then laid the bricks in place using an air setting mortar building up to the point where the arch would spring from. At this point we put the Fibre bats in the space between the bricks and the foil. An arch form was constructed and the arch carefully built by cutting side arches from straight bricks. We were lucky enough to have a brick saw for this and consider it would be well worth while hiring one for the job. Once the arch was set in place and the flue built, fibre was put in above the arch and all gaps and the weldmesh roof bolted down. It was then an easy task to line the door by laying it flat on the ground and layering the fibre, making sure that no joins went through to the next layer. We then lifted it in to position and used ceramic cups and anchors to hold the lining in place. All it needed then was for the burners, spyholes damper and pyrometer to be put in place and the kiln was ready to fire.

Like all first firings it took a little to get it right but Lindy has now fired 100 times and has it to the point where she feels that she can confidently predict the results of each firing and can experiment a bit with settings. It is slightly cooler at the top but generally it fires evenly and consistent and we can recommend the design to any one who wants to build a kiln.

®Leonard Smith