my wood kiln
Finally, 2 months after moving to Rahu Road in May 2014, I’ve managed to get to work on the re-building of my wood kiln. I am lucky in that the previous owner created a good platform in the ideal spot on the property for a kiln. I started by creating a boxing for the foundation and compacting a clay and stone mixture into the form work for a sturdy level base. Then it rained and I needed to re-do about half the mixture, so my focus moved to creating a roof to prevent more delays by the weather. A dilapidated shed provided the cladding and roof trusses, the poles are in the ground and soon I’ll be able to work in the dry.
The roof is up and I've started laying the concrete blocks to create the different levels from the firebox through to the chimney. That done I filled them with a compacted mixture of clay and gravel. When I moved the kiln the bricks were all mostly sorted into type and from which main area of the kiln they were used in, however in my hurry to get them off the truck I ended up stacking the pallets in the wrong order. So I've been hauling bricks up the hill to the kiln site and re-sorting them to make sense of what bricks go where. This is a slow process and hampered by wet weather. But I've finally managed to rebuild the firebox - a little taller (2") than last time as I'm keen this time around to put bigger pots in the firebox and fire them for longer. When my brother turned up with his kids for the holidays I put them to work hauling bricks up the hill and laying the foundation bricks under the chamber and chimney. One of the pinch points in the kiln build this time is the need to clean every brick, either scraping off old mortar or grinding off glaze burrs. This slows down considerably the process of laying bricks.
The worst of days of grinding are over, so now the walls are starting to grow quickly and the risk now is to forget to check the plans and lay too many bricks without inserting spies or soda ports. I had a slow time when tying together the walls as the outside bricks are red commons, the inside firebrick, which are different sizes and require a novel approach to connect them. When I finally got up to the skewback level it was a relief. I've gone for more of a steel cage look this time around, still using bolts and no welding (I don't have a welder). I've also scaled up the steel skewback support beam to prevent the slight flex which occurred in the last kiln. When I came to use the arch former that I built to demolish the previous kiln it needed tweaking, more height was needed, proving that the arch had flattened slightly (1") over time.
Finally the main arch is sprung and tapped into place. Then I hauled out the firebox arch former to finally spring that curve as well. Now it's mostly a matter of building the chimney out of my fast dwindling brick supply and then insulation and firebox grate etc... The chimney build went quickly as I had to use the bricks on edge to gain the height I needed. The slowest bit was building the stabilising frame, heat shield and flashing.
I had to have a bit of time off kiln building in November and early December so when I got back into business I built a wood shed and the deck around the outside of the kiln. Just the insulation and front of firebox left to do. So waiting for the summer storms to give over and let me back outside! And so summer finally arrived, allowing me to finish off the grate, firebox front and insulation on both the firebox and main chamber. So pretty much all done before Christmas.
The kiln had its maiden firing on the 9th May and performed very well. Another firing happened on the 14th July which incorporated a few successful tweaks to the bagwall. This configuration is as easy to fire as the last version with firing of 13 and 13.5 hours to an even cone 11. Now its a matter of getting in the wood and using this marvellous tool.
Click on the working plans for a more detailed PDF version.