Sunday, August 6, 2017

How the wood fired kiln works!


Back in the mists of time, when I last posted I did promise to upload some photos and information about the kiln and how it works. The kiln is rather unusual, but is showing signs of working very well, and I do hope that some of the design ideas might help someone else to make a kiln.

I think that the ladder type grate shows a lot of promise, and may well make a very welcome alternative to someone who has battled with a more conventional design. The other refreshing thing for me was to find that the single firebox with entry flue at the back left hand corner made it perfectly possible to have an even heat distribution front to back in the kiln, and only a 2 cone variation from top to bottom. Having the shelf over the firebox may help with this, and it is certainly a useful "bonus" place to put an extra pot or two in the kiln.

Chamber with front shelf removed to show flueway to chimney under shelves. Inlet flue is visible at the left rear of the chamber.

Loading kiln. Back shelf stack full, front stack incomplete.

Loading kiln. Front and back stacks of shelves full.

Chamber door bricked up 6 inches thick with 2 layers of insulating fire brick on edge.

Fire box door in place. Small fire lit under ladder grate at beginning of firing.


Chimney damper on left used to control the draught through the kiln. Right side of chimney no longer in use since alterations to the chamber.

Kiln in daylight with metal drum of kindling rather blocking the view!

Kiln firing at night. The first firebox door was an old ceramic fibre lined dust bin lid!

In February of 2017 I demolished the external firebox and stripped out the interior of the kiln. The following are photos that I took of the rebuild.

Kiln stripped out leaving arch and back up insulation bricks.

Floor of chamber was made on a foundation of concrete blocks that are laid on their sides.

The chamber floor consisted of one layer of standard fire bricks over a layer of insulating fire bricks. On the left the firebox is under construction.

The floor of the ashpit is two fire bricks thick to help protect concrete foundation slab from excess heat.

The actual floor of the firebox has an air gap under it. I used some large second hand fire brick slabs to make this floor.

Fire box nearing completion. Large fire bricks make a ladder grate.

Firebox from the front. "Ladder" just visible.


Heavy large fire brick slabs form the top of the firebox.

Relining the chamber side walls and back wall is complete and the permanent left hand front wall is under construction.

The left side of kiln almost complete. Concrete blocks that are under the chamber will be left "open" so that any build up of heat inside them is allowed to escape.

A kiln shelf covers most of the firebox inside the chamber. A gap is left in the rear corner to form an inlet flue. I initially thought I would use a single stack of 18 x 24 inch shelves in the chamber, but decided that 2 stacks of smaller shelves would make stacking the kiln considerably easier, the shelves less likely to bend or break, and offer more versatility.

Hope the photos have been of help to someone. Apologies if they have been rather slow loading due to their quantity, but I thought it useful to have them all in the one place.

I am happy to try to answer any questions regarding this kiln, but do regard what I have made as a starting point! The shape and size of the kiln was dictated to some extent by the kiln shelves and other materials that were available to me. You may well have other materials on hand, so could build quite differently.

4 comments:

Anonymous said...

Looks great - thanks for all the details and pictures!

Peter said...

Hi Anonymous,
Good to hear from you. It was a pleasure to finally get the photos into some sort of order!

Anna said...

makes me wish I had a wood firing kiln... I'll be sharing your post to Facebook as I think it could be very useful.
Trust you are keeping warm as I think you had some fierce winter storms this year.

Peter said...

Hi Anna,
It is nice to hear from you all the way from sunny Australia! We started unusually warm this morning, but the sky is now grey and it is much cooler. Some talk of a thunder storm this afternoon! In our recent big storm the main road about 200 meters North of us turned into a river, and 2 or 3 houses were flooded. Our side street also was under water, but we sailed through it all on a little "dry" patch of land rather like Noah's Ark!

Thank you for sharing this post, that is much appreciated. I think that people may have assumed my blog had finally ground to a halt lately, as I haven't posted as often as I should have... but we are still here!!