What is Charcoal?
Charcoal is wood that has had almost everything but the carbon removed from it, almost as if it were 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 most of the sap and 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 chamber without allowing excess oxygen inside and then keep it sealed until it has fully cooled again.
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?
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 particles that clog the airflow as it burns. We also like the idea of diverting wood scrap from the waste stream and turning it into something useful. Creating a clean, efficient 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 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 well because they are softwood, clean, dry, bark-free, nail-free, and short enough to fit in the charcoal kiln without sawing. Tree removal is sometimes a good source of Red Pine, the material of choice for swordsmithing in Japan.
Our charcoal cooker is based on a small version of a traditional Japanese charcoal kiln. This design uses a steel chamber buried in clay soil that insulates and seals it to ensure that only enough oxygen comes in to facilitate the cooking without consuming all of the charcoal. With careful monitoring the heat from the combustion gasses “steams” or cooks the wood into charcoal without burning it up to ash. The kiln is covered with a roof to keep the soil dry and doubles as wood or charcoal storage space between batches. There is a stone work area in front of the kiln for sorting wood and charcoal. Read more about the kiln here: Charcoal Kiln V.4.
Once the dry wood is split into appropriate sized pieces and stacked loosely almost to the top of the kiln, the kiln is mouth is closed with bricks and stones and sealed with earthen plaster. A fire is started inside the small intake opening 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. After several hours, the smoke changes to bluish and almost clear indicating that the water is gone and the wood has been converted to charcoal.
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, the chimney is blocked and all openings to the kiln are sealed with bricks and clay plaster to be left overnight. After a couple of days the kiln can be opened and the finished charcoal inspected. Depending on the moisture level of the wood and the fire monitoring, more than 90% of the wood should be cooked and less than 10% will remain as brown charcoal, needing to be cycled again in the next batch.
Chopping & Sorting
If all has gone according to plan, the wood has turned into shiny black charcoal and is very light and brittle sounding when tapped but not overly crumbly and soft. It is chopped and screened into 1-2 inch cubes and stored in a metal container awaiting use in the forge. Depending on the type of work, one kiln load might yield enough charcoal to do the forge work for two or three large tanto. 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.4
Read about using charcoal as a fuel for blacksmithing: Sustainable ‘Smithing?
Follow our charcoal making progress from its experimental beginning: islandblacksmith.ca/tag/charcoal/