Part 2, Building a Small Scale Wood Fired Kiln, the Details

Building any kiln can be an expensive proposition. In building my version of Steve Mills' Backyard "Philosophers" Kiln, I wanted to build it for as cheap as possible, which meant taking time and committing to the long haul of collecting materials.

Free PDF of Steve Mills' Backyard "Philosophers" Kiln: https://tinyurl.com/mr3vjcmyBook: https://tinyurl.com/yc6kuvkh

Mills' Backyard Kiln uses a single layer of perforated and solid regular house bricks. These tend to show up in online marketplaces and salvage yards and might be an easier, low cost material to source than new firebrick. I was fortunate that a friend/mentor gifted me with all the bricks I needed (a diverse mix of hard and soft firebrick in a variety of shapes and sizes), plus the kiln door, a few posts and cordierite shelves that I used for the dampers and interior shelf insulation.

With my hodge-podge of bricks, my kiln ended up being slightly smaller than the instructions. The bricks I had are all 9" x 3", but the thickness varies - 2", 2.5", 3". I have 7 1/2 bricks in length x 3 across x 15 tall (a mix of all the sizes of bricks).

The book called for a metal pipe as a chimney. I ended up having enough soft brick for the chimney as well as adding an outside insulation layer to the kiln chamber, neither included in the book.

The damper was also optional. As I had enough bricks for the chimney and, when it comes time post-firing to shutting everything down, it seemed like an important feature. I chose to put in two narrow dampers, one on each side of the chimney.

I used a mix of hard and soft brick with the faces flat to the kiln chamber for extra insulation. Using the face of the bricks will help to reduce air intake through the cracks between the bricks of the main chamber, plus I had a fair number of double width soft brick that were perfect for the insulating outer layer.

Everything is secured with angle irons, galvanized wire and turnbuckles on all corners of the chamber and the chimney.
The dimensions from angle iron to angle iron of my kiln:- 68" long x 38" wide (includes 5" of insulating bricks) x 44" tall (from base layer to top of chamber)- Chimney is 78" from base of chamber to top which rises 13" above the metal roof and is approximately 7" above the tallest point of the roofline.- Chamber dimensions: 45" long, 32" shelf space with 13" opening at end for air, 16" wide x 16" deep. Works out to about 4.7 cu/ft of loading space.

Mills suggests that his kiln:chimney dimensions and ratios conform pretty close to Fred Olsen's Kiln Book recommendations. I guess time will tell if that's the case with my version.

The kiln shelves were another big challenge. The book (a UK publication) calls for 2" thick shelves which, as far as I can tell, do not exist in the US. All new shelves are really expensive, silicon carbide for wood kilns significantly more. I reached out to a couple of area potters and discovered a regional FaceBook clay forum. I did an ISO post and within hours had a source for used silicon carbide shelves for cheap (6 16" x 18" and 2 18" x 24" - most slightly warped and some with cracks, but okay for my needs - $100) and some free 12"x12"x1.5" cordierite shelves. I had to drive 2 hours to collect the silicon carbide shelves and another hour for the cordierite, but well worth the time and effort.

There are a lot of options online for the kiln door designs and one suggestion in the book. Again, I am deeply grateful for the gift of my stout welded door.

Things I had to buy:
Angle iron I sourced from my local welder/metal scrap yard, about $45 total.
Galvanized wire and turnbuckles from Lowe's, 18gu wire - $15; turnbuckles - 5 @ $5 ea.
Kaowool fiber for the door and top of kiln. I bought 2" thick, but ended up skiving it all down to 1" and doubling the amount of coverage. The 2" thick x 48" x 16" piece, $70; 2" x 16" x 24", $37. Various sources on Amazon. ** July 2024 update: bought another 2"x24"x75" piece of kaowool for additional top insulation, $80
Digital pyrometer from Amazon, $90, https://tinyurl.com/56fn3z7n
Nichrome wire, 20gu from Amazon, $10
Concrete blocks for base, Lowe's $3 each
Cement board, Lowe's $15

We decided on a nice "stick built" pole barn and spent about $1200 on materials. There are lots of options for salvaged carports, "make-do" coverings or none at all, but we wanted something that added to our property value and looked nice.

The floor of the barn is about 4" of compacted ground slate hauled from our neighbor's recent well drilling project, non-flammable and free.

I plan/hope to fire this kiln to ^10 in one day. Everything I've read makes me think it will get there.

I hope this helps folks see that building a small scale wood fired kiln can be done with minimal materials and humanpower. It's a lot of work, but I know it will be worth every sore muscle and hour of labor!