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trouble with my coal


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i started blacksmithing about a year and a half ago and while its not a big problem, i have noticed that as the coal i use in my forge begins to catch it tends to stick together forming large clumps. i was just wondering if there was a way to prevent these clumps without needed to break them up with the poker from time to time.

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Hey

My coal does the same thing, and it happens with every other person's coal forge I've used. I've never been bothered by it, I have simply accepted it as something that happens. The impurities as they are getting burned out tend to stick together which is what causes the coal to do that. It's all part of the coking process I imagine.

If it bothers you that much, you could always switch to coke, and I think that problem would be eliminated.

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LOL, you are seeing a desirable characteristic in a quality met coal, the coke button or free swelling index. With this property you can bank your coal around the blast, it will coke and form an oven. by husbanding this formation you can use less fuel to get the same work done. Once the coke is formed then green coal is coked on the sides to replenish the walls as the interior is used up. This keeps the smoke down as you forge.

Sounds like some good stuff.

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LOL, you are seeing a desirable characteristic in a quality met coal, the coke button or free swelling index. With this property you can bank your coal around the blast, it will coke and form an oven. by husbanding this formation you can use less fuel to get the same work done. Once the coke is formed then green coal is coked on the sides to replenish the walls as the interior is used up. This keeps the smoke down as you forge.

Sounds like some good stuff.

Mills
I am also 'green' although I knew the coking was a good thing, I am not sure that I am tending my fire correctly.
My coal forms coke readily. but it is such a solid mass that I inevitably wind up with an empty oven. What is the process for keeping good coals below and not winding up with too much oxygen on my steel?
Should this oven have a top?
Should I not be sprinkling the coal with water because it cokes so easily?

The answer may be what I am doing, which is to simply bust the coke up when I loose the 'floor' and then bank with more green coal around and above it - or is there a better way?

I am using an old rivet forge and I use fire brick to give me some depth. I have never considered the coking a problem, but wonder if I could manage my fire smarter.
What are the best techniques and/or alternatives for husbanding the fire?

Thanks,
Bill
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All fires will burn hollow after some amount of time, which may only be a few heats depending on the fuel. I usually make a "valley" and continuously pack it from the sides. The piece is laid on the bed of burning coke and more loose coke or coal is raked in on top. When the piece is removed, the fuel on top usually falls into the bed. The process continues with each heat, insuring the fire doesn't become hollow.

An enclosed "beehive" or "oven" fire is also OK but you'll have to feed it from the front with coke as green coal will make a smoky fire and will not heat properly until the coal has coked.

A good way to visualize the difference between coal and coke is that they are similar to wood and charcoal. Both coal and wood have volatiles that give off radiant heat but typically forging and welding heats are not possible until those volatiles and any residual moisture are driven off and the fuels convert to coke/charcoal.

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ok so thats a good thing lol thank you all very much for your help but i have yet another question about the matter. whenever i see videos of, i guess pretty well established blacksmiths from the looks of them, the coke in the fire tends to be loose and more free moving allowing the metal piece to get deeper into the fire... i guess my real question is this: how do i keep my coke like that? it seems like it would be much easier to manage then the "oven" shap that i usually get now.

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My coal tends to stick together if I coke it quickly on top of the fire so I use that when I want a hive fire. When I want a lose fire I just push the coal in from the sides slowly as I need it and if it sticks together I just give it a whack with the poker. Come to think of it I give it a whack even if it does not stick together because its about 1" coal and I like to have it smaller in my fire so when it cokes I break it up with the poker anyway.

Cheers

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When coal is heated it releases a great number of different chemicals. One of the first things that happens is the release of coal tar. This is what is binding the lumps of coal together. It is also the cause of the heavy yellow/brown smoke that you see. These are some of the different chemicals which are being released from the tar and some of which are highly flammable. This is the large flame produced after the coal has been heated to a high enough temp. for the tar to break down. There are way too many chemicals in coal to list here, especially when talking about those released from the tar. After these various chemicals, gases,tar etc. have been driven out of the coal, what remains is carbon, called coke.

In coke ovens under controlled conditions , this leftover coke is almost pure carbon with some sulfur and a few other trace elements left behind.You don't achieve the same level of pure carbon when you make coke in your fire due to the fact that the temperatures where the coal is "Roasted" do not reach the higher temp or air tight conditions found in coke ovens. That said however, the coke you do produce in your fire burns at a higher temp. than the coal itself does enabling you to obtain the high temperatures used in forge welding. there is also little or no smoke given off as most of the volatiles have already been burned off making your coke in the first place.

Some of the tar remains even after you have "partially" coked your coal and this is what keeps it bound together. A simple matter to break it up into usable sized pieces with your poker for use in your next fire. This is in fact what you are aiming for when you build your fire is to have some coke for your next fire in order to have a nice clean burning fire with a minimum of smoke and good heat.

Ok Class Dismissed. The instructor is getting off the soap box now.

Terry

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Not to sound too wise and knowing, First time I ran into the problem described I had been using anthracite coal, no coking at all. Just shovel it in. I ordered some known good coal from Kayne (Blacksmith depot now) and was VERY upset when It wouldn't get as hot as the coal I was using. I was shoveling it in and it would swell and choke off my air supply. I crank harder and pour on more coal! :lol: After going through 25 lbs pretty quick I began to realize that this stuff was acting like jiffy pop. That is when the terms of coking and free swell index became a real description rather than a nebulous term bandied about by the old codgers who would laugh at neophytes such as myself.

Anyway, from a totally green coal start, get it lit and burning and smoking. It swells and smokes more. Poke a hole in the top and let some flame out. The flame burns a good portion of the smoke and we are on our way. a few minutes of air supply and there should be a decent amount of burning coke maybe even going to hollow already. push in from the outside so that the coke breaks free like a glacier and gets into the party. use the poker to break it up a little. experience will teach you how much fussin to do with "herding" the coke into the fire. As you do more green coal is coking on the outside and rebuilding the wall. This can be configured in many ways. I generally kept the top clear and used the sides and back to create reflective walls. The front was where I had a path of coke and ash, the top so I could watch. When forge welding I would create the oven. Long pieces I only had the two sides or sometimes I would make a bridge.

In a young fire there is coke and it is plastered together with green coal starting to coke. Then there is green coal. This is what it seems you maybe having trouble with. As the fire matures there is sufficient time for the fire to coke the walls such that there isn't a dividing line between coal and coke. It is more of stages. I also found that the more impatient I am the more I create a solid mass that I am always having to break up. Another discovery is that there is no hard and fast rules for handling YOUR coal in YOUR forge. I watched everybody else and tried to pick up better techniques from observation and analysis. Mainly I slowed down. That may not be your problem. You'll have to decide how much advice applies.

That sums up my knowledge, I can clarify any of the above, if asked.

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Two basic types of smithing coal fires: Open and Closed.

Open is a big heap of coal and coke that you shove your piece in and generally you can't see how hot it is till you take it out. Great for heating though as the contact is much closer to the metal.

Closed is the "oven fire" where you have walls of coked coal around an open area. Great for billet welding or tasks where you want to jusdge the hear very carefully as you can often see into the "door" of the oven to judge temp.

Both take manipulation to work with:

For an open fire you break up the coke into chunks so you can slide the metal in without hitting big slabs. As it burns you add more coal around the sides to coke up and be broken up and raked into the using part of the fire.

For a closed fire you need to replenish the coke and resize the oven area. I generally do this by taking the coal shovel or slice and starting at the sides and aiming toward the tuyere shove it in breaking the side walls and filling the hole with coke from the side walls. The top usually drops some too. I then add more coal in a thick layer across the top to allow it to coke up and provide the roof and fill in the sides which have been shoved into the middle.

Boy I sure wish the coal out here in NM coked into big slabs like the Poco I used to get in OH!

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