Tregear Pottery

Building the kiln

After many months of discussions, grant applications, researching plans and costings the first real sign of activity at the site was the arrival of Glen's digger.

The site, at the rear of the sawmill, though well chosen in terms of access to the all important supply of wood, presented real difficulties for access with any large equipment.  From the outset we were determined to minimise any impact on the surroundings. In the event the digger had to be taken in and out of the site via the garden and the adjoining field. This short but eventful journey had to be undertaken with great care, both to avoid the digger getting stuck and to prevent it from churning up the ground.

Throughout the early stages of construction each time there was a 'lull' as we waited for materials, expertise or money, the spare time was used to stack and cover huge quantities of firewood in preparation for the first firings. Though I knew these firings were, in all likelihood, many months away, I was also well aware that to achieve the temperatures I sought the wood would have to be exceptionally well seasoned and dried - anywhere between 6 months and a year. Having cleared and levelled a sufficiently large space the site was measured and the preparations for the foundations commenced. To support the many tons of brickwork and nearly 20ft high chimney it was essential that there was an ultra strong base to build on. We built a reinforced 'raft' foundation . Several cubic metres of ballast and cement had to be carefully lifted by crane as close to the site as we could manage. We worked late into a very wet evening, mixing and moving barrow after barrow load of concrete. Our enthusiasm and tenacity proved crucial to the kiln's success, not only in the build but also during the later firings.

With the foundation complete the next challenge was getting the insulating bricks to the site. Approx. 1200 soft insulating bricks and 300 hard firebricks were delivered from Swansea to a yard in Portsmouth. From there an island carrier brought them to Cowes. This valuable cargo was then loaded onto a smaller lorry to bring to the kiln site. However, getting such a tall lorry down such a long and narrow track was far from straightforward. The lorry slowly progressed down the track as we walked ahead, cutting off overhanging bows along the way. Then we had the problem of trying to ensure the lorry could turn around at the far end of the lane.

With a tail lift that could barely support the weight of the brick pallets the unloading process was not simple either. Once the bricks were finally in the yard our difficulties were far from over. The pallets proved too heavy and unstable for the timber yard crane to lift. This meant that all 1,400 bricks and 50 concrete blocks had to be carried by hand to the kiln site! I ended up carrying out this task single handed over several days. Only once all the materials were finally in position and safely covered from the rain was it possible to start the building process.

The brickwork was surprisingly quick. It took me approximately three weeks of full time work. Each course of bricks has to be carefully checked - square and level. The insulating bricks are very lightweight and can be cut with a conventional saw. The entire construction process is an immense act of faith - until it is fired the kiln is merely a structure.

Bourry Box kiln

After much research I had chosen to build a 'Bourry Box' type kiln. The initial design for this type of firebox was first published by Emile Bourry in 1880 under the title of 'A treatise on the Ceramic Industries of France'. Bourry did not design the firebox but simply noted its existence. This type of kiln was used at the Sevre Porcelain factory to fire hard porcelain to temperatures in excess of 1,400 degrees centigrade. It seems likely that the actual design was developed at the Limoges factory. The factory needed to be able to fire porcelain to very high temperatures without marking or damaging the delicate surfaces and colours. In the 18th/19th century wood was the only available fuel.

The firebox, the all important powerhouse of the kiln, incorporates a ledge half way up the inside. Logs rest on this and are ignited by the pile of embers beneath. The kiln utilises the principle of only burning preheated air. This is vitally important if the high temperatures are to be reached in a short space of time.

With the onset of gas and electricity this design was largely forgotten. In the mid twentieth century Michael Cardew succeeded in constructing what was probably the first English bourry box kiln. In recent years the design has experienced something of a revival as many potters around the world seek to use wood, both as a sustainable fuel source and for the unique effects only available through woodfiring.

The overall kiln design is based on a very precise set of proportions that ensure sufficient space is available for combustion and sufficient 'draw' is provided by the chimney. Using this formula I was able to draw up a set of building plans that would show how every one of the 20 or so courses of brickwork were put together.

To build the all important shelter we waited on the delivery of some chestnut trees that would provide exactly the right quality for the posts. The building would provide essential protection from the weather. The lightweight insulating bricks would quickly deteriorate if they were exposed to the winter rains. The shelter must be sufficiently tall to ensure there is no fire hazard from the kiln. The team at the timber yard have extensive experience in the construction of this type of building.

Once the large posts are cut, holes are dug and the posts cemented into position. The roof timbers quickly followed. Our metal roofing was salvaged from a demolition site in Ventnor.

The metal framing that completes the kiln structure is cut, bolted and welded into position. All of the edges of the kiln are braced with heavy duty angle iron.

"My part in all of this was to design and install the metal bracing system that holds the kiln and chimney together allowing for expansion and contraction as the kiln heats and cools. We worked at night, a solitary arc lamp illuminating our exhalations in the cold air, as we cut metal, drilled concrete and slowly strapped the kiln together. Climbing the chimney to bout the last of the metal straps in place was like the final pat on the back before sending our children out into the wider world! I visit the kiln from time to time just to see how it’s holding up and I still get a little swell of pride when I think about my small part in the big dream." Michael Watson

Once the roofing is in place the remaining six foot of chimney is built. The 15 foot high chimney is essential to provide the powerful 'draught' that will be required to pull the huge flame power through the kiln chamber. In late autumn 2007 the kiln is finally ready for its first firing. This is the moment of truth, up until now the entire project has been design and construction.

"We helped light the kiln the first time. During the other firings we brought Dad and the others some supper to keep them going. Sometimes they cooked a pizza on the top of the firebox! It was very, very smoky." Mia Tregear

"We told Blue Peter about our part in the kiln project and we both received Green eco badges!" Ishbel Tregear

" I discovered Neil's wood fired kiln because one of the walks in the Walking Festival included a talk from the potter on site. I then realised he had come on my Alexander technique for Potters Workshop some four years earlier and I was glad to help with firing. I watched as he grappled with this kiln that has so many variables influencing how it performs. There was such a process of discussing, experimenting, analysing, theorising, going back to reading again what has been written on the subject. Rebuilding it. Putting into the context of the practical – how to coax it, does it need more draught here or here? Is it affected by gusty wind? Then being rewarded by the upwards response of the pyrometer, or hopes dashed by its stubborn refusal, or loss of heat. Organising ourselves so the stoking was not back breaking. We tried moving away from watching the pyrometer constantly, to judge the fire’s needs by hearing the sound of the flames, which worked well at certain stages. How important were the cups of tea and cakes!" Shella Parry.

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