When it comes to forging a knife, heat is a critical factor in determining how easy it will be to work the steel as well as the quality of the final product you’ll end up with. Hot, consistent temperatures in your forge is a necessity, and the fuel source that you choose helps determine that temperature as well as your cost of forging and more.
Of the various fuel types available, the primary 3 to choose from are lump coal, propane, and charcoal. Depending on the availability of the fuel, the forge you are using, and the local laws governing your workshop, there may be an ideal option for you to consider. However, if you’re unsure or are just starting out, consider charcoal – the fuel you can make yourself.
What Determines the Temperature Charcoal Burns At?
As heat is incredibly important to the forging process, it makes sense that the fuel you choose needs to burn hot enough to get the blade to critical temperature so that it can be shaped, annealed, and hardened. However, unlike fuels such as propane, charcoal can come in various compositions that determine its burning efficacy, and it also needs an exceptional amount of air to allow it to reach the necessary temperature.
In order to produce fire and extreme heat, combustion needs to occur between oxygen, the fuel source, and something to ignite it such as friction or another heat source. Once the fuel reaches ignition temperature, combustion occurs and it burns on its own as long as it has oxygen and fuel for combustion. You can also increase the air availability, increasing the rate of combustion and leading to more heat being released by the burning charcoal.
To introduce more air to your forge, you have some options. First, you want to make sure you have proper ventilation so that the air in the forge is rich in oxygen rather than smoky and inefficient. Once your ventilation is cleared, you can add more air with a hairdryer for smaller forges, a bellow for larger forges, and custom air blowers for the largest of forges.
Composition of the Charcoal
Charcoal comes in primarily 2 different forms: lump charcoal and charcoal briquettes. In general, briquettes are used for cooking due to the odorless burn and ability to flavor what you’re cooking depending on the wood used for the base of the charcoal.
Meanwhile, charcoal is used where more extreme heat is needed because the absence of the other ingredients allows for more fuel to burn. Lump charcoal comes from burning wood, making it entirely charcoal as opposed to briquettes of charcoal which are a combination of char, coal, nitrates, lime, and starch.
Based on this information, it is hard to determine exactly how hot the charcoal you may use could get in your forge. As a general rule, you want the steel you’re working to reach about 2,000-2,200°F to be malleable. Meanwhile, lump charcoal is believed to be able to reach temperatures of about 2,000°F at its upper range – which explains why it’s crucial you use lump coal instead of briquettes.
Should I Use Charcoal for My Forge?
When it comes to choosing the fuel source for your forge, the choice is primarily up to you as any of the 3 primary fuel sources can work for some applications. However, each has their own pros and cons – charcoal included.
One of the major benefits of choosing charcoal is its availability as well as low cost. You can make lump charcoal yourself by burning wood until it chars, making it both easily renewable and inexpensive if you’ve got extra firewood or trees around. Here is a quick video that shows the process of how to make your own charcoal (it’s very simple)
Unfortunately, depending on the composition of the charcoal, it can struggle to reach and maintain the necessary temperature needed to make the steel for your knife malleable. This means that if you want to use charcoal, you will need to use pure lump charcoal as opposed to briquettes. Additionally, it takes more charcoal to reach and maintain hotter temperatures than coal or propane – the other choices for fuel.
Charcoal is often considered the lesser of the 3 fuel choices for your forge due to its lower burning temperature. Steel needs to be heated to upwards of 2,000°F in order to be forged, but charcoal can struggle to reach that in some cases which makes it a bit too unreliable for many blacksmiths. However, that is not to say that charcoal can’t be used – it just depends on your specific use case.
Smaller forges and those who smith multiple metals (with lower critical temperatures) may be able to make charcoal work for them and given the availability of the fuel (and your ability to make it yourself), it is quite beginner and budget-friendly. It won’t hurt to give charcoal a try, and if it works for you then you’ve got a low-cost, renewable fuel. If not, just choose coal or propane for your next forging.
-THE STAY AT HOME DAD
UPDATE: Links to all items updated Feb 08 2020 and added budget-friendly pre-built burner choice. Unless you already have most of these parts it will be far cheaper and faster to order a pre-built burner. I use this one in my forge and kiln and it's never let me down. As an added plus, it comes with a high pressure propane regulat...
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