What is Charcoal?
Charcoal is wood that has had almost everything but the carbon removed from it, basically it is wood-shaped carbon. These are the black bits you can find the next morning after a campfire…don’t throw them away, they burn very well! Charcoal burns very hot and clean because the water and sap and most of the other substances in the tree have been taken out. The way to remove these things without burning up the charcoal is to heat it inside a container without allowing any oxygen inside.
Why do we use Charcoal?
For the last couple of hundred years most blacksmith shops in the west were run on mineral coal because it was cheaper, easier to store, and more readily available than charcoal. For thousands of years, though, charcoal was the fuel of choice, and to this day in Japan and many other countries, blacksmiths and swordsmiths still use charcoal for their work. Pine is the preferred wood for bladesmiths. Charcoal is very clean burning and is healthier for the ‘smith and the high carbon steel.
Why do we make our own Charcoal?
We like the idea of diverting wood scrap from the waste stream and creating something useful with it. To our knowledge, no one in North America is selling softwood charcoal so making it is the only source for now. Barbeque charcoal, usually made from hardwood, does not release its heat as quickly and tends to break down into smaller, heavier particles that clog the airflow as it burns. Creating a useful fuel source from scrap is a fulfilling task and working with softwood charcoal is a pleasure that every ‘smith should experience.
Making Blacksmithing Charcoal by Hand
The small batch process we use takes about an hour to prepare and load the kiln, between two and six hours to cook, overnight to cool, and about two hours to chop and sort the finished charcoal. When the wood is dry and well stacked, one batch provides approximately 6-8 cubic feet of chopped charcoal, up to one full 55 gal. drum.
The raw material for our charcoal is deadfall or standing dead pine or short pieces of construction and mill waste wood. These scraps of wood normally end up burned or in the landfill unless one of our local construction, milling, or woodworking friends calls us to pick them up. These pieces work perfectly for us because they are softwood, clean, dry, bark-free, nail-free, and short enough to fit in the charcoal kiln without sawing. Thanks to all who have provided their great scraps to us!
Our charcoal cooker is based on the design by Iwasaki~san, which is a miniature version of a traditional Japanese charcoal kiln. The design uses calculated opening sizes and chimney length to ensure that the oxygen coming into the combustion chamber is used up before the flue gasses travel through the charcoal chamber. In this way the heat from the flue gasses “steams” or cooks the wood into charcoal without burning it up. The kiln is easy to tend, operates at a fairly low temperature, and does not have the burn out issues of higher temperature retorts. Read more about the kiln here: Charcoal Kiln V.3.
Once the dry wood is split into smaller pieces and stacked loosely almost to the top of the charcoal chamber, the kiln is closed and covered with an insulation layer. A small fire is started in the combustion chamber and soon the chimney begins to produce very wet, low temperature steam. The purpose of maintaining this fire is twofold, to create heat for driving out water and impurities, and to use up the oxygen coming into the kiln. Depending on the size of the wood inside, after two to six hours, the smoke changes abruptly to bluish and almost clear. This is an indicator that the water is gone and the wood should be mostly converted to charcoal but not overcooked yet. Within five minutes, we seal all openings to stop the process and let it cool.
If the kiln is opened while the charcoal is still hot, it will burst into flame and all of the charcoal will turn to ash and be lost. It is important to keep it sealed as much as possible and let the kiln cool completely before opening it up. For this reason, we remove the chimney and block all openings to the kiln with bricks and soil mixed with ash and leave it overnight. The next day we open the kiln and check the finished charcoal. If the kiln is insulated on the top and the sides, at least 90% of the wood will be cooked and less than 10% will be brown charcoal that will need to be cycled in the next batch.
Chopping & Sorting
If all has gone according to plan, the wood has turned into shiny black charcoal and is light and brittle sounding when tapped but not crumbly and soft. We chop and screen it into 1-2 inch cubes and store it in metal containers awaiting use in the forge. One kiln load might yield about three galvanized garbage cans full, depending on the type of work this should be enough charcoal to work for several days to a few weeks in the blacksmith shop. We often run two or three batches one day after another but one good one is enough to fill up the large metal bin in the shop. The video below shows some of the differences between good softwood bladesmithing charcoal and poorer quality “overcooked” biochar type charcoal.
Sumi Kiri San Nen
There is an old saying that it takes three years of concentrated work to learn how to chop charcoal. For an idea of how to properly chop charcoal, watch the real swordsmith Pierre from Montréal performing Sumi-kiri, the art of charcoal cutting. The videos below show the basics of chopping and sorting charcoal for bladesmithing.
Read more about the charcoal kiln here: Charcoal Kiln V.3
Read about using charcoal as a fuel for blacksmithing: Sustainable ‘Smithing?
Follow our charcoal making progress from its experimental beginning: islandblacksmith.ca/tag/charcoal/