Forge: Fuel

Progress on the forge is going slow, mostly because it is very cold outside and I have not made much more fuel for it. So I figured now would be a good time to go over how the forge is/will be fueled.

Traditional forges were fueled with charcoal. Eventually coal was discovered and has been used ever since. My forge is being fueled with charcoal, because it is easy to make for free. I work at a hardware store with an indoor lumberyard. The lumber is shipped with many smaller pieces of wood used for stabilization. This wood is scrap, and is discarded as the lumber is taken off of the stacks. I occasionally collect this scrap wood and take it home. Once I have enough, I use it to make charcoal.

Simply put, charcoal is wood burned without access to oxygen. There are several way to do this. Traditionally, charcoal was made by making a large pile of wood, covering it with a light layer of dirt or sod, then lighting it. The covering restricted the flow of oxygen so that the pile burned very slowly, but very hot, with very little oxygen. This method was good for creating very large amounts of charcoal, but the quality was lacking, since some of the wood had to burn to ash in order to provide enough heat to turn the rest into charcoal.

A less efficient method of making charcoal is to place the wood in a container that has only enough venting for exhaust gases to escape, but not enough to allow oxygen to flow into the container. The container is then placed in a hot fire until the wood inside has been turned to charcoal. This method generally uses more wood to provide heat, but results in very clean charcoal. It is also better for smaller scale operations. This is the method I use. I have used empty aluminum cans (most of these are actually made of steel; aluminum would probably melt), paint cans, and a small metal garbage can. Paint cans can only be used a limited number of time, as they tend to corrode quickly. I have found aluminum cans to be generally too small for reasonable batches (I used juice cans). The garbage can works well, but it might be difficult to keep the lid on, as the can can build up some pressure. The garbage can I use has an unusually shaped handle that will keep the lid on when it is up.

The wood I am using is fir. Normally, charcoal is made from hardwoods, but I have read of issues with that type of charcoal. Others have found the hardwood charcoals produce more ash, often enough to clog and restrict airflow through the forge. The fir charcoal I am using does not produce significant amounts of ash. Fir charcoal is not as dense as hardwood charcoal. This means that I have to use a lot more charcoal to run the forge than if I was using hardwood charcoal. So, this is a trade; better forge operation, at the cost of having to make and use a lot more charcoal.

I may have come up with a solution for this problem. The compressed wood pellets used in pellet stoves are fir (the ones we sell where I work are, anyhow). These are far denser than normal fir and may even be as dense or more dense than hardwoods. In a few days, I am going to use a juice can to make charcoal out of some of these pellets. The can is full, so it will probably take a long time, since the amount of wood in the can is much greater than usual.

I do not know if ash will become an issue. Compressed wood charcoal will produce more ash when burned, but my use of normal fir charcoal has not produced even enough ash to build up a little bit (it seems that the ash is so light that it quickly floats out the forge as it is produced, but the volume is not large enough to see it leaving the forge). So, I do not know if the increased ash production will be significant.

In addition, the fuel pellets are smaller than the pieces of charcoal I normally use. This means higher burning surface area. This should cause the forge to burn much hotter. I may have to restrict the airflow into the forge to moderate the temperature. The compressed wood should last longer in the forge as well, since there is higher mass of wood. I may have issues keeping the pellets from falling down the hole in the bottom of the forge (which is used to force air into the forge), but if this fuel works well, I will design the new forge to work with it.

Once again, I will post more as I learn more, and as things progress.