Efficiency of charcoal

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thegeek574

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Sep 3, 2010
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Everyone,
I had a question on forges. How efficient is charcoal compared to propane? Will you get more forging time out of an charcoal as you will with propane, assuming the same amount bought ? is there any specific reason I should go either way? I have enough room for just about anything. money, however, is limited. thanks,
Steven
 
Wow, you ask the tough questions.
Charcoal can have a certain amount of water adsorbed on the surface and absorbed into the pours while propane will be essentially water free. Charcoal will have a certain amount of ash in it while propane will be very pure. Propane will burn cleaner than charcoal. I dont know the exact numbers for charcoal (it can vary from @ 50% to 90% Carbon by weight depending on how clean it is). I'd guess (educated) that, if the charcoal is less than 1/2 the price per pound of propane, and your charcoal forge is running at maximum efficiency, then charcoal could break even. From my reading the charcoal forge can have areas of excess carbon (carburizing) and areas of lack of carbon (excess oxygen or decarburizing) while a propane burner will be set as a reducing or oxidizing or neutral flame. So you could more easily normalize or anneal steel in one area of the charcoal forge while heating another piece of steel to forge in another. In a propane forge you might have to change the fuel to air mixture on the burner when normalizing or annealing versus forging, but this is supposition. Remember, you can use coal or coke also. This is an interesting question for me so I hope others will chime in.
 
In a small setup like I have, a 20# (BBQ size) propane tank costs me $15 to fill and lasts a long time. I simply turn it on and within a few minutes I'm up and running.

I will throw this out though--using coal over propane for most makers is probably not a matter of efficiency unless they're getting it for free, or have a free/cheap supply of hardwood and are making their own. For some it's the tradition of the method, and for others it's a matter of control over what portions of the blade you want to heat. A tube-shaped forge chamber heated with propane doesn't allow you to heat just the edge or just the spine of the blade, for example.
 
for inexpensive forging mineral coal (bituminous) is your biggest bang for the buck, however it does have issues with things like sulfur which will make some steels go red-short. My propane forges use between 3/4 and 1 1/2 pounds per hour, more if I am welding

-Page
 
Well, thanks for the responses. I have a massive supply of potential charcoal, but it just needs to get here. that is the problem, becuase I can't drive myself places. I have enough brush to keep a small army supplied, but I don't think little stuff works too well. it has some larger stuff in there, but not too much.

The mention of coal brings up a few questions. How many people like it, how efficient is it, and where can I buy it? I am in the Portland, OR area.
 
I have been all through the forge fuel thing. Having made and bought charcoal, bought coal and coke, and built and used my gasser I can just tell you my opinion.... Each had advantages and disadvantages. Charcoal burns clean and gets plenty hot, but it takes a bunch of it compared to coal/coke. Coal has to be coked before it is much use, coke works great and the only disadvantages are clinker buildup and poor availability in my area. The most efficient use of my time and money is gas, but the size and shape of what I can get in the forge are quite limited compared to my solid fuel forge. Also with the SF forge you can more accurately and easily heat small sections of the work.

As far as heat treat goes, I heat treated a lot of blades with charcoal with varying degrees of success and it took a LOT of practice to get consistently good results. With the gas forge I can just dial it in to the desired temp and get great results every time.

Your situation is no doubt different than mine but I ended up with 2 forges, 1 gas and 1 SF. They both get used depending on what I am doing.
 
Cool. I think I will go with coal/coke if I can find a supplier in my area, but I will go with propane if I can't. Also, what is the minumum diameter of wood for making charcoal? I have a lot of stuff in between 2 inch and 1/2 inch and I will use it if I can.
 
I make my own charcoal for use in a small coffee can forge that I use for heat treating 1080. I make charcoal by building a fire in a Coleman 5067-700 Outdoor Hearth Fireplace and snuffing out the fire by putting the lid on it and letting it cool down (about 12 hours) I find that pieces of 2x2 can be converted to charcoal but pieces of 2x4 will have unconverted wood in the interior. This may be a function of the size on the hearth/fireplace. From one burn I can get about seven or eight gallons (in five gallon buckets) of charcoal. Hopefully you will have a better system to make charcoal that can effectively use larger pieces of wood. Charcoal burns up pretty rapidly and you would probably need quite a bit to do any amount of blacksmith type work.

- Paul Meske
 
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