As part of the island kajiba project, reclaimed and natural materials were used to construct a larger traditional style charcoal making kiln. The basic concept is a simple chamber with a door on one end and a chimney on the other, insulated and sealed by being buried in clay/soil, and roofed to keep off the rain.
After more than six years of successful forging with charcoal made in the Charcoal Kiln V.3, the kajiba project afforded the opportunity to create a more permanent kiln for making charcoal. The Iwasaki kiln, a scaled down and modified version of a traditional Japanese charcoal making kiln, is relatively easy to build, load, tend, is long lasting, makes consistent charcoal batches, and is still my first recommendation for those wishing to begin learning to make charcoal for blacksmithing and bladesmithing.
Other than size, the main difference between the Iwasaki~san’s design and this traditional style charcoal kiln is that there is no separation between the combustion chamber and the pyrolization chamber other than the fuel materials and kiln loading itself. Carefully controlling the airflow into and out of the kiln during operation is the key to making quality charcoal with efficiency. Materials used in this project were mainly earth, stones, reclaimed wood, and scrap steel that was on hand.
Laying the Foundation
A stone bed/pit under the chimney with a buried pipe to drain excess water as it condenses.
The base of the chimney is a large chamber to prevent clogging due to build up of condensed tar.
The drain pipe and the base for the chimney, plenty of scrap used in this project.
Reclaimed roofing provides a bit of a vapor barrier from the ground, the kiln will be raised off of it by a few centimetres to help heat retention.
Fabricating the Interior
The location of the chimney, in this case a six inch diameter steel pipe from an early retort experiment.
The opening to the chimney chamber, pulling from the bottom rear of the charcoal chamber.
A colourful visitor to the kiln during construction.
The floor slopes slightly down toward the back of the kiln to move the coolest air toward the chimney.
A piece of heavy corrugated steel roof provides some space for draft along the floor and adds strength.
The remainder of the piece provides insulation and strength across the top of the kiln.
A view into the kiln, the door is fairly large but will make loading and unloading easier.
Building the Frame
The frame will serve to support the roof as well as contain the soil that insulates the kiln.
The tapered shape of the kiln is visible, moving the rising heat towards the back of the kiln.
Three layers of reclaimed sheet roofing are used to contain and insulate the soil.
Repurposed roof peak covers the open ends of the roof corrugation and keeps the soil from falling out.
Stones and sloped soil around the outside to assist drainage away from the kiln.
Ready for filling with a clay/soil mixture, large stones form a working area in front of the door.
The interior of the kiln tapers from about 3’x3′ at the door to 4’x4′ at the back.
Insulating with Soil
The space to be filled around the chimney assembly.
View of the space along one of the sides and some of the stones supporting the kiln.
The narrowest area at the corners will still provide about 8 inches of insulation.
A large volume was required to fill around the chimney.
The structure handling the weight of the soil well, once the moisture comes out it will be lighter.
The chimney will sit flush with the surface as it will need to be sealed with soil after each firing.
Ready to build the roof before the rains come.
Roof and Finishing Details
Building the roof using available scrap wood.
Finishing the front of the kiln with stones and backfilling with soil.
The door is currently made of stacked stones, all of the gaps will need to be sealed with clay/soil mud during operation to control airflow.
Heavy steel protects the roof from the heat of the chimney, brackets and shelves for storage.
More brackets for storage on the rear wall.
The stone paved work area in front of the kiln is partially protected by the roof overhang and will be used for splitting wood as well as unloading and sorting charcoal.
View of the kiln with the kajiba, see the whole building project here.
Slowly drying the soil insulation before winter with a small scrap wood fire in the kiln.
A curated video playlist of making and using traditional charcoal kilns in Japan, the first two videos are for swordsmithing charcoal, followed by other styles mainly for cooking and grilling charcoal:
