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Matthew Freyer

Charcoal Forging Truly Superior?

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Hey everyone,

 

I had a question about the superiority of forging with charcoal. I have heard from a lot of different sources that charcoal (and in particular pine charcoal) is the best fuel for forging fine steels like one would use for knife blades and quality tools etc. Is there some science out there to back this up (or is this a "sacred cow")?. It seems that people go to pretty extensive efforts to make kilns,retorts, etc. to make charcoal and I wondered if it is simply for the aesthetic (not in any way to say that it isn't awesomely cool) or if there are real practical benefits to forging with charcoal. I would love to know people's thoughts on this and did not find any other threads that addressed this specifically.

Thanks! :)

-Matt

 

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Hello Matthew!

Well, I have been using charcoal for quite some time before I switched to anthracite (price reasons). For me, it had several benefits - I got high temperatures quite easily even on quite massive stocks, and when I was welding, I didn´t need to wait every time I added a handful of coal, since the charcoal is quite clean. At least this is my experience.

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Forging with charcoal has a certain aesthetic appeal and you don't have to burn it down to coke to get rid of sulfur fumes like coal but you will do a lot of fire tending and some days it will seem that you can't keep a good fire going to save your soul. Gas is easier to keep a good fire going and it's a lot cleaner. I started out with charcoal and I have to admit that I miss the fire you get with it, just not that much. It does have the advantage of being able to have an open fire with no wall around it to forge irregular things like axes.

 

Doug

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Not science perse, but in my [limited] experience, there are a few major differences that have been discussed a little already. Propane is much more predictable, especially for things like welding (cleaner) and heat treatment (able to hold much more exact temps). However, propane is generally more expensive than charcoal/coal/coke. As far as being superior, the heating can sometimes be more centralized, and in most places solid fuel is much cheaper than gas. On the few occasions when I have made my own charcoal, pine was the go-to because it was plentiful and easy to reduce to a hot, clean burning charcoal. I have heard a number of places that, as far as charcoals go, soft woods like pine are superior to hardwoods, although I am not entirely certain why. I think it might have something to do with the nature of its sap and how that interacts with the volatiles as they burn off, but that is just my speculation. And of course, there is the mythic image of forging in solid fuel that helps :rolleyes:

 

John

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Well in South Florida propane is the most available and better priced alternative. When in NC I buy coke by the sack to burn to show my friends the traditional way to forge. I used some pine charcoal once. I used all I had and finish the blade in a coke fire. It burned hot and clean but, so did the coke. I regularly use propane.

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Oh hey, seeing as you're in Arizona Manzanita should be around you, and it is really good for fuel, increases temperatures in a simple woodstove drastically.

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Hi Everyone,

 

Thank you everyone for the comments! Very helpful so far. I life in Flagstaff AZ which is right in the middle of a HUGE ponderosa pine forest. So pine firewood here is usually very cheap/free and also very dry (since we have a very low relative humidity typically). This has spurred my interest in pine charcoal as I love the traditional aesthetic of a solid fuel forge and coal is not readily available around here (I think the closest supply of "good" coal for smithing is the coal mine in Hesperous Colorado, near Durango (about 5 hours from here). It is pretty hard to beat FREE, even if it comes with a little extra work. I had read and heard that charcoal was the "best" for making things that we want to be sharp, but I wondered if that was just tradition and myth or if there really is something to it. Is it the lack of sulfur in the charcoal that makes it better for steel? Is this a real issue, or is it just a sales pitch? When we forge doe we get to temperatures where the sulfur can impact the steel, or is that just an issue in smelting?

I have a propane forge, and I also have a bellows-blown forge that I have built in which I burn scraps of wood (essentially making charcoal and forging with it in the same process). I am wondering if pre-pyrolising the wood into charcoal is going to produce a much better fire in the forge since I won't be using so much energy to convert the wood into charcoal at the same time.

Also, I wonder about the different forge environments (propane, coal, charcoal) in terms of the amount of carbon present. If I want to heat my steel in a carburizing (sp?) environment, do any of these fuels have an advantage or is it just how you adjust the fuel?

Thanks again for the comments (and for putting up with NUGs (New Useless Guys) like me! Any thoughts you might have would be helpful.

-Matt

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I think what you're hinting around is whether one fuel can improve carbon steel. by driving carbon into the steel or some other such thing. The short answer is, no. You cannot carburize iron in any kind of open system. If you pack iron into a closed box with carbon bearing material (dung, leather, hooves, wood) and cook it for long periods, you can drive enough carbon into the iron to make it case harden. If the iron is in thin sheets you can create blister steel. But you can't do it accidentally.

 

Charcoal is no better or worse for the steel, so long as you aren't burning or over heating it. High sulfur coal is bad for steel, it tends to make it brittle.

 

I understand the emotional tie to "traditional" methods, however, coal did not become the preferred fuel for smiths until the 1840's, and gas forges date back to the first Pennsylvania oil strikes of the 1859-1870 period.

 

Charcoal making was a huge industry in England and Europe in the modern era, but primarily because you get less smoke (think how smoky big cities were in 1800, and how that was better than burning wood) and because you are not transporting the water and other volatiles contained in the wood. OTOH it was a full time job for 4-6 people to keep 1 blacksmith in operating fuel. So you have to ask yourself, you want to be a blacksmith (or bladesmith) or do you want to be a charcoalier. Just because the base material is "free" doesn't mean that the process is without costs.

 

Geoff

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Well put, Geoff. When I made a few batches of charcoal, it was an all day affair, and that was for about half of a 55 gallon drum! It is, unfortunately, not something you can 'fire and forget'. The retort needs to be watched carefully and tended to ensure the charcoal you are making does not combust with the volatiles. And of course, there are other methods of fuelling forges beyond propane that are not amongst the solid category. Natural gas works fine, and if you can get it right, waste oil, diesel, and I have even heard mention of kerosene, although I am sceptical of that. And straight electricity for induction forges. I suppose for me it is a battle between feasibility, availability, and cost. In the end, propane has won every time.

 

John

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The only thing I would add is that soft wood charcoal like pine or fur is that is burns very very fast. You can get very good heat, and make good forge welds with it. But, and there is always a but. Soft wood or even hardwood charcoal burns about 20 times faster than coal does. So you need a mountain of it to do any work for any length of time. When Japanese sword smiths make their swords, they will go through literally tons of it throughout the process. Charcoal has its benefits, but I prefer high grade blacksmithing coal. It last as much as 20 times longer, and I can reuse it as coke the next day.

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I stick with gas as it gives instant and controlable heat, and I don't enjoy smoke getting in my eyes...although I do use charcoal for annealing large batches of steel blanks, first getting them up to heat in gas, I move to charcoal which I choke and let cool slowly.

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FYI - the coal from Hesperus , Colorado is no longer available to the little guy and hasn't been for quite a while unless something has happened in the last month or so - they have a contract with one of the coal fired power plants so sell all they mine for that purpose only...besides the last stuff I know that came out of there is way too sulphury for good forging - it's a real pain to use...

 

PS I live in Durango only an hour away and IMO what they've been mining for the last few years wouldn't be worth the trip even if they did sell it in small amounts....

Edited by Wild Rose

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I think what you're hinting around is whether one fuel can improve carbon steel. by driving carbon into the steel or some other such thing. The short answer is, no. You cannot carburize iron in any kind of open system. If you pack iron into a closed box with carbon bearing material (dung, leather, hooves, wood) and cook it for long periods, you can drive enough carbon into the iron to make it case harden. If the iron is in thin sheets you can create blister steel. But you can't do it accidentally.

 

Charcoal is no better or worse for the steel, so long as you aren't burning or over heating it. High sulfur coal is bad for steel, it tends to make it brittle.

 

I understand the emotional tie to "traditional" methods, however, coal did not become the preferred fuel for smiths until the 1840's, and gas forges date back to the first Pennsylvania oil strikes of the 1859-1870 period.

 

Charcoal making was a huge industry in England and Europe in the modern era, but primarily because you get less smoke (think how smoky big cities were in 1800, and how that was better than burning wood) and because you are not transporting the water and other volatiles contained in the wood. OTOH it was a full time job for 4-6 people to keep 1 blacksmith in operating fuel. So you have to ask yourself, you want to be a blacksmith (or bladesmith) or do you want to be a charcoalier. Just because the base material is "free" doesn't mean that the process is without costs.

 

Geoff

 

I would be careful about about making an absolute statement like " You cannot carburize iron in any kind of open system. " I will be glad to show you how I can carburize in an OPEN charcoal fire or even in my propane forge.

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Jesus,

 

I'd like to know more about that. Perhaps you could start a new thread?

 

Geoff

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Awesome everyone. Thanks for the input! I appreciate the sage advice on the advantages of propane giving more time to focus on bladesmithing itself. I am judging based on the responses that most people do not believe that there is any advantage to charcoal forging blades, which if I am correct they would put this in the same category of "hype" as forging blades only during a full moon, quenching while facing north and chanting ancient norse nursery rhymes during tempering.

On another note I am very interested in Jesus' comment on the ability to carburize in an open forge environment. It sounds like the fuel is not as much the issue as is the technique if I am understanding his comment correctly.

I love this forum!

-Matt

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Yes, sulfur fumes from coal can be absorbed into steel while forging and cause brittle inclusions. That's why you want to start out with a low sulfur coal and then burn it to coke before moving into the center of the fire. The late Bill Moran used to burn a batch of coal to coke, put it out and then store it for future work. Beats having to purchase blacksmithing coke. If you thing that you might want to use coal/coke I would recommend that you watch The Making of a Knife by Bill Moran. You can get a copy from the ABS store on it's site.

 

By the way, a lot of things can be used for solid fuel forges. There have been those who skip the burning of the wood to charcoal and just use chunks of wood. Cracked corn has been used. Even read an entry once from a man that said that he used dried horse manure.

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I'm a charcoal enthusiast.

At the school where I'm studying, there seems to be a silently agreed upon truth that no real work can be done without smithing coal or propane.
I hate the propane setup they're using in a small log-cabin type shop. Everything gets hot even with all doors and windows wide open, regulating the pressure is finicky and prone to being affected by the room temperature, and the noise is unbearable. And propane is expensive here, about 1000$ for a couple of days of full-blast forging.

 

The coal, specially imported smithing coal from Germany, cost more than the nicest hardwood barbeque charcoal at the local supermarket.

It is also flaky, high clinker and very volatile. When it's coked up it's lighter than burnt toast.

So when the teachers and other students have gone, I deepen the hearth 3" with firebrick, and go fetch my 10 lb. bag of charcoal from my car. It's more than I can use in a 6 hour session for light bladesmithing.

 

John Page found making charcoal time-consuming. I haven't made hardwood charcoal yet, but my experience with making charcoal as a byproduct of making pine-tar is a happy one.

First of all the retort needs a heat-source, and it's a delight to be able to burn and make use of all sorts of junk you don't want to bother making into proper firewood. Half rotten wood, boards with nails or dirt etc.

We use an old cut off waterheater on it's head, it's about 50 gallons. (It's stainless, and it's sturdy 1/8" walls are a real help for making tar since the wood has to be sledgehammered in there real tight.)

This used to be quite fuelconsuming, but the addition of walls and a lid (steel roof panels) has cut the fuel usage by a factor of 10. Also they mean we can have a less intense fire, which gives a higher quality tar, with more volatiles and a lighter colour.

One burn takes 4 hours of sitting around with a cold beverage, chucking on a little fuel now and then.

For making charcoal it could be done in 2 hours, and you wouldn't have to put any effort into packing it just right, but if you want good tar it's best to take it slow.

 

But if it is a superior fuel for forging?

All else being perfect, no.

-But if, as in my school's case, the coalforge flue is inferior, your nose will thank you, and you'll save alot on the kleenex budget.

-Or if your management of a coal fire is lacking, welds might go easier with charcoal provided you have a deep enough hearth.

-Also noone here has been able to tune up the gas forge yet. If it's the lack of skill or it's just low quality I do not know, but it barely reaches welding temperature, and makes alot of scale. Under my circumstances charcoal is just easier and more predictable, and I won't have to depend on others for my fuel supply.

 

There's just less that can go wrong with it.

Edited by Steffen Dahlberg

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Geoff, there is no need to start a new thread. Go over to the bloomers and buttons section and search for Aristotle furnace or Ole Evenstad. The process of carburizing iron in an open charcoal fire has been described there.

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I burned charcoal, and took awhile to learn to control the fire,you can burn a piece of high carbon steel in charcoal in no time . Propane forge is a little simpler , you can control the heat better, no flue and hood to worry about. No embers to burn your arms .it realy pros and cons .

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I do like Doug mentioned above, and burn wood. I don't know if it's 'better' per se, but it's free fuel; works for me. The wood chunks pretty much process themselves into charcoal as you go along...sometimes you have to wait for a good coal bed to do some particularly hot task, but usually just throwing in a few fresh wood pieces after every heat keeps it all going very well.

 

I have welded small things in the wood fire; larger pieces have failed, but I think it's more a lack of firepot depth, than a problem with the fuel.

Edited by Orien M

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