JHCC

Recommendations for Working with Anthracite

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In many places, soft/bituminous coal is hard to come by, but anthracite/hard coal is more readily available. In the USA, many Tractor Supply Company (TSC) stores will carry anthracite, usually in "nut coal" or "rice coal" sizes. This can be used for forging, but it presents some challenges. This has been discussed elsewhere on IFI; this post is an attempt to put the bulk of that information in one place.

CAVEAT

As noted below, bituminous coal, coke, and charcoal are all superior to anthracite as forge fuels. That's not a point that needs to be argued. However, this post is not intended as advocacy for anthracite as a superior or even preferable fuel, but as a practical guide to its use for those who -- for whatever reason -- have no access to regular smithing coal or coke.

ABOUT ANTHRACITE:

Among the various types of coal, anthracite has the highest carbon content, the greatest hardness, and the highest energy density and is lowest in ash and volatile compounds. "Nut" and "rice" are measurements of size, not content: nut coal will fit through a 1-5/8" x 13/16" mesh, while rice coal will fit through at 5/16" x 3/16" mesh.

Because anthracite does not have the bitumen/asphalt content of soft coal, it does not coke. This means that anthracite will not form a "cave" of coke as bituminous will. Instead, as it burns, each lump will become smaller and smaller until its carbon content is completely burned away, leaving behind roughly 8-13% of its dry weight as ash. In practice, therefore, nut coal will pass through pea-size on its way to becoming rice coal, and rice coal will become barley and buckwheat on its way to its final destination as ash. Rice coal, in my experience, has a tendency to spit and pop as it heats up, and I've had glowing shards projected out of the fire at high speed. (One left a scar under my right eye, and another -- when I was turned towards the anvil and my back was towards the fire -- flew down the cleft where my back changes name. Wear eye protection and a shirt.)

The absence of volatile compounds and its high density also make anthracite much harder to light than soft coal, coke, or charcoal. With bituminous coal, a fairly small amount of heat will vaporize those compounds and cause them to ignite; this in turn provides sufficient heat to vaporize and ignite the solid carbon. Without those compounds, that heat has to come from somewhere else. Additionally, because there is no burning of volatiles to create and sustain a draft of moving air and because the higher density of anthracite reduces the air:fuel ratio (especially compared to coke and charcoal), constant blower use is mandatory to keep an anthracite fire going. (The trade-off here is that anthracite burns much cleaner than bituminous, with a short blue flame and very little smoke.) 

One thing to look out for is that anthracite often has pieces of shale or other nonflammable rock mixed it. I've even found chunks of wood. Just pay attention to what's going in the fire, and it shouldn't be a problem. Also, most bagged anthracite gets watered down before bagging, to help control dust. Rice coal seems to have more water per bag than nut, but that's not a problem if you put it on the outside of the fire and let it cook off.

LIGHTING:

In order to start an anthracite fire, then, you'll need a lot of heat. This can be accomplished in a couple of different ways, but I personally have had the greatest success by using a LOT of kindling. Start with a ball of newspaper and some fine softwood slivers, then add some fine hardwood kindling (about 1/4" square) and then progressively thicker, up to about 1/2"-3/4". (NOTE: make sure your kindling is hardwood. Softwood doesn't put out enough heat to get anthracite going. I cut up pallet wood on the tablesaw to about 3-4" long and then split it on the hot-cut.) Adding a candle stub to the pile also helps get things going nicely, and you can also put a few pieces of lump charcoal on top to help get things going. Light the newspaper, and gradually increase the blast. Once, the kindling fire is well-established, pile coal around its perimeter. Gradually add more coal around the outside, forming a sort of "anthracite volcano" with the kindling fire as its core. When the kindling fire is going strong, you can start to sprinkle small pieces of coal on top, but make sure to leave the top open to allow heat and burning gasses to escape. Gradually increase the blast and keep adding coal until your fire is going well.

FIRE MAINTENANCE:

As noted above, anthracite does not coke, but simply becomes smaller and smaller until it burns away. Therefore, fire management is slightly different from other coals, and is actually somewhat more like how one maintains a charcoal fire. 

Because anthracite doesn't coke, an anthracite fire doesn't hold its shape as well as a bituminous fire. Expect things to move around a lot, and be prepared to make liberal use of your rake to reshape the fire every time you put your workpiece back in the fire. You can add coal directly on top of the fire, and you won't get the clouds of smoke that would result from doing that with green soft coal. 

Make sure you have a constant supply of air, or your fire will go out. An electric blower on some variety of speed control is best, but a constant-speed blower with a gate or air dump will work. Deadman switches are a gamble, as the fire tends to go out if you have to step away from the forge for any length of time. Hand-cranked blowers and bellows only work well if you have an apprentice with nothing to do but pump the fire. 

You'll probably find yourself reaching for the watering can a lot less with anthracite than with bituminous; at most, an occasional sprinkle around the outside to keep the fire from getting too big. However, since there's no need to wet down the coal as it cokes (because it doesn't), you're probably better off managing the fire size by regulating the strength of the blast. 

Clinker production will vary depending on the specific batch of coal and what your forge is lined with. Because anthracite burns pretty hot, it will tend to melt the surrounding dirt fill and make some pretty monumental clinkers if you let it. If your forge doesn't have a clinker-breaker, try this procedure every hour or two.

  1. Build up a nice big fireball and run it hot and hard for a couple of minutes. This will melt any bits of clinker lurking within the fire itself and let them sink down to the bottom.
  2. Reduce the blast to a bare minimum and let sit for a moment or two. This will allow the collected clinker to congeal.
  3. Rake the burning coal to one side, off of the clinker.
  4. Remove the clinker with a poker, rake, or tongs. Make sure the tuyere opening is clear.
  5. Push the burning coals back into the firebowl and increase the blast.
  6. When the fire is going strongly again, resume forging.

If you don't clean the clinkers out regularly, they will form their own networks of air passages, creating hot spots and (relatively) cool areas within the fire. You don't want that, especially when welding or heat treating.

 Otherwise, anthracite fire maintenance is pretty simple: regulate the blast to give you the size of fire you want, and keep adding coal around the sides and on top. Expect to keep 2-3" of burning coals piled on top of your workpiece at all times. Remember that anthracite's greater energy density means more heat than an equal volume of bituminous coal, coke, or charcoal; build your fire accordingly.

PUTTING OUT THE FIRE:

Because anthracite requires constant airflow to burn, the easiest way to put out an anthracite fire is simply to cut off the air. If you like, you can rake the burning coals off the top to disperse the fire's thermal mass; that will cool things off a bit faster. I usually just leave the fire alone at that point, which means that the clinkers are quite cold when the time comes to set up the next fire.

Because you should never leave a lit fire unattended, I recommend shutting off the blast, raking back the burning coals, and then letting the forge sit while you put away your tools, sweep the floor, neaten up a bit, etc. By the time you're done, it should be safe. If you're pressed for time, you can pull back the coals and lightly sprinkle everything with  your watering can. You don't need to drown it; you just need to cool it off enough to make sure it won't reignite.

A WORD ABOUT VENTILATION:

Because anthracite doesn't produce the voluminous smoke that a bituminous fire will, you can get away with a slightly smaller flue than normal, if necessary. (I've even used an anthracite forge with no flue at all in the middle of a double-wide garage with the door open and a big stand fan running.) However, even if there's no visible smoke, your fire will still be putting out carbon monoxide and sulfur dioxide, neither of which you should be breathing. The big kindling fire necessary to get things going will also put out a lot of smoke at the beginning. In short, whatever your setup, make sure you can exhaust any smoke and fumes effectively and that there's a sufficient supply of fresh air coming in.

CONCLUSION

If you expect anthracite to behave like bituminous coal, coke, or charcoal, you will be setting yourself up for frustration and failure. The key to success is to approach anthracite on its own terms, with a clear understanding of how you can use its properties to your benefit. I hope this helps. Good luck!

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You have put a lot of time into this article. Congrats. 

However, in many places your comparisons between met coal and anthracite are quite the opposite.

No quotes, but I'll work thru some highlights.

Yes, when you look at the specs, anth appears cleaner than met coal. And has a higher carbon content. However, what you are missing is that when met coal cokes the impurities are burnt off and coke is pretty close to 100% carbon and it is nearly impurity free.  Charcoal is, in this sense, cleaner than met coal.

A cardinal rule, especially when doing tool smithing and especially forgewelding is that you want to keep any and all "green coal" out of your coke fire and away from your steel. There is absolutely no way you can keep green coal away from your fire,, it Is your fire. This is why from a blacksmith perspective, anth is "dirtier" than met coal. Because any coke is far "cleaner" than even the best anth.

Concerning air. You are correct, you need more air in your working your fire and more air to keep it going when at the forge.

As to the first, working the fire. Quite simply more air means an oxidizing fire, and our iron, especially forge welds and tool smithing(including knives) strongly prefer a neutral vs oxidizing fire. You can reduce the air to nearly zero, and maintain a forging fire with very little added o2 in a coke fire.

As to the second, when working more than one piece of stock, that extra air you need will scale far more due to the o2, and it's far easier to burn your work by a magnitude,,,  no matter if you are working many irons or just a few small pieces.

Starting a fire: well the only time I use anything but a piece of newspaper to start my met coal fire is my first fire ever. This is the smokies fire I ever have. After that I use a match, newspaper, and coke left over from the previous day. Coke doesn't smoke, so again, keeping that green coal out of the fire prevents a smokey fire. And the time to start every fire after the first takes about as much time as it takes to turn on your ox/acetyl, run out your hoses, and light your torch. 

Maintaining a fire: I have never used water on my coke fire because___ "its coke. thus with no coke I can use less water." I use water liberally always to control my fire size,,, from a small slit fire for tempering springs to a large fire to work multiple irons at a time.

And you are correct, with anth you control your fire size with air. And when working multiple irons, there that bugger called an oxidizing fire. And a small slit fire is really hard to maintain for the very reasons you state. It falls apart each time you pull your iron from the fire.

Smokey fire: I never,, let me repeat,,, never do I put green coal on the top of my coke fire. It smokes like a son of a gun, and contaminates my coke. 

I work my fire in this manner:

 Coke in the firepot surrounded by "green coal" which is burning off all impurities(the green wispy trails) surrounded by the other coal reserves. As the coke burns to clinker and ash, it goes down thru the clinker ball, and never blown up and out where these fines will contaminate your coke and plays hades with your iron. Not to mention breathing that stuff when it is in the air.

Then pull the fresh made coke into the center and maintain ~2" coke on top. No cave. Hollow fires suck, in more ways than one.. pull coal in to fill the green coal stash.

Then add more fresh coal as needed to your forge. 

And last, but already sorta mentioned, never leave a fire unattended. With a hand cranked blower, as soon as you quit cranking, the air supply decreases. Thus no burned iron, and when the air stops completely, your fire is literally out. Out such that when I take a lunch break, say, I dump the ash, prop the ash gate open a bit and put a small log round in the top, and i have a safe "cool" coke fire waiting for at best a handful of wood shavings if a crank on the old blower doesn't do the job. 

In conclusions, there are reasons to use either, but it's best to understand both in order to make the best choice,,, and there are very good reasons that met coal is used by the steel industry and is called "blacksmiths coal."  

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Thanks for the feedback, anvil. To be clear, I'm not saying that anthracite is preferable to bituminous (what you call met coal/metallurgical coal). Rather, this article is intended to act as a guide for those smiths who do not have access to bituminous, so that they can make the most out of what's available to them. 

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I realize that. And about the only reason I can think to not use met coal (thanks for spelling it out) is when you are just starting out, do not know where to get it, and do not want the ease of just going to Tractor supply.  

Expense is an initial factor as well. However I believe every state has an ABANA affiliate. This, especially in my part of the world, can be expensive. But the longer you "play in the flame", the easier it is to justify a two day journada to buy a ton at ~80$-100$ a ton. This is certainly out of the question till you truly are bit by the bug.

And a big compliment on your article. Your layout is something I lack. A fine example of a well thought out piece!

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Without a doubt, charcoal is cleaner than coke, and coke is cleaner than anthracite. 

I dont believe the relative difference between charcoal and coke is  much, but the relative difference between coke and anthracite is,, "appreciable".

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I think we can take it as read that bituminous coal, coke, and charcoal are all superior to anthracite as forge fuels. That's not a point that needs to be argued. However, this post is not intended as advocacy for anthracite as a superior or even preferable fuel, but as a practical guide to its use for those who -- for whatever reason -- have no access to regular smithing coal or coke. 

I know it's futile (and ironic) for me to ask that an IFI thread stay on topic, but I would be grateful if we could stick to a practical discussion of anthracite on its own terms. Thank you.

That said, regarding the issue of an oxidizing fire, this is less of a problem than it might appear. As long as your fire is sufficiently deep and you have balanced the strength of the blast with the volume of the fire, you will still have a neutral center and a reducing top layer, the same as with any other fire. Anthracite's inability to "idle" simply means that the air necessary to maintain the fire has to be injected mechanically rather than drawn in by the natural draft of the fire. In other words, it doesn't change the fuel:air ratio.

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A sequence of photos showing the building of an anthracite fire. 

Space cleared in front of the tuyere.

D26AD091-3BA3-46F5-9779-9C8097471A7E.jpeg

A ball of newspaper.

D11CFBDD-A204-470B-AB33-38513DE52634.jpeg

A handful of softwood slivers.

DB841D42-A823-4515-AB62-1BF51092ACFA.jpeg

Fine hardwood kindling.

1D40E519-C38A-4AFA-A26E-042095228F25.jpeg

Chunky hardwood kindling and the first bits of coal around the kindling pile.

E2D1C173-AC22-49A6-A675-182A8B2C6AA0.jpeg

Kindling lit and first bits of coal on top.

88066987-832A-4E1E-BDEA-BDCC7F65BD58.jpeg

Fire well-established and coal starting to burn nicely.

6AD7F1EA-15E2-4459-ABFD-E13ECEAE4BDB.jpeg

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John, Well done..   

My experience is right on par with what you wrote..    

As to only an oxidizing fire..  This is not the case..     It comes down to how the fire is managed just like a charcoal fire or a soft coal fire, or a wood fired forge or a gas forge, or and oil forge.. 

With enough fuel addage to create a balanced air to fuel burning fire, the hot spot or neutral (heart) is still created..  forge welding is the same..   

I always marvel at how despite  a million or billion or how many ever people there are it still becomes  "ONE's" perspective on how things are done and then the ability to share it.. 

Working with someone, doesn't mean you possess the same skill set or the same level as this famous person..   

I always teach for the student to have the ability to be better than myself.. IN other words I teach so they can have the tools to potentially be better... It's up to them to adapt and use the tools given to them.. 

I do things much different than others here.. YET, it is the same. 

I don't pay homage to difficulty of use or skill set..    ONce you own the basics.. You own it all..    Is one thing harder to make than another..   "NOPE" Just takes longer.. 

If I were to add anything to this thread in the use of hard coal is that the depth of the fire may need to be deeper  than soft coal or charcoal or coke..  In order to get that sweet spot because of the constant air flow..  

Other aspect which is over looked in all solid fuel forges is " Always manage your fire with the future use in mind"..  5, 10, 15 minutes out to anticipate your fuel needs to create the amount of coke or hot burning hard coal or commercial coke..   This way the fire will always be ready for the activity at hand..  (forge welding, heat treating, tempering etc, etc).. 


Great work John..     Really a great write up for those that want to know.. 

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Oh, and of course 1 other thing..    

NO need to bank up the coal like with soft coal...  Use firebrick or a fire ring or ducks nest to create a deeper fire when needed..   Instead of building up coal to support the fire which can lead to the fire being wider than wanted vs only deeper.. 

This will keep the fire contained and make the fire be far more manageable vs just controlling it with air like a softer fuel source.. 

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Great read, but were can I find the "ideal size" pot size for my only local sourced TSC nut

  • Anthracite
  • 40 lb.

. Plus optimal BTU blower requirements. 

I want to get this build right the first Time. So many conflicting options in here, I'm not sure what to do?

PLEASE direct me towards any useful information on this.  i'll attach a 3d drawling I put together per info on u tube... ?  

it seems too deep to me but hey what do I know.....  That why I am here!  

Thanks & Peace Out!   

forge.png 2.png

Edited by Mod34
Excessive quoting

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As I recall some TSC's don't carry coal during the summers and so you may need to stock up near the end of the season.  Might talk with the manager about buying what's left at the end of the season at a substantial discount... (I've made such deals with stores before; they get to clean out inventory *fast*; I get stuff I want cheap!)

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"Optimum" is as much a function of what kind of work you're doing as it is of the kind of fuel you're using. Take some time to read over the posts in the Solid Fuel Forges section, and proceed accordingly.

One good option for you would be to start with a JABOD forge and use that to learn what size firepot will be best for your work.

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yes thomas I just got off the phone with her when I posted, she recommended the same thing. Thanks 

Edited by Mod34
Excessive quoting

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I feel for all the folks who finally learn how to forge with anthracite; only to learn it won't be available again for 6-9 months...

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On 1/24/2019 at 7:54 AM, JHCC said:

"Optimum" is as much a function of what kind of work you're doing as it is of the kind of fuel you're using. Take some time to read over the posts in the Solid Fuel Forges section, and proceed accordingly.

One good option for you would be to start with a JABOD forge and use that to learn what size firepot will be best for your work.

oh believe me I have read up in here as much as I can, yes I've read about JABOD.  I just want someone with real world experience to tell me , yes looks good start there or no way dude your a xxxx xxxx do this...  I built a small brick ribbon burner now I'm looking for what I need to get to larger pieces of mainly decorative dressings on my silo house. . I have stair railings & balcony's, door knockers & large cedar wrought iron door (i'v already built but needs dressing)  all the way down to drawer pulls, shelf brackets & such.  See this is what I'm doing for my retirement. This in my fun time to enjoy life.  Peace Out!  

Edited by Mod44
language

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I would recommend starting a new thread in the Solid Fuel Forges section, asking for recommendations on a firepot design. Give the graphic you have above and include the information you just posted. Most folks won't see the question, if it's buried here.

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I guess I can try....  not sure if it's appropriate for a newbie to start new threads...  at least in my tech groups I belong to they frown on newbie threads...  

55 minutes ago, Silo house Dan! said:

 

what does this mean? Edited 28 minutes ago by Mod34 
Excessive quoting

 

 

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Newbies posting to ask for information is only frowned upon if it's clear that they haven't done their research first. Asking for help on a specific question and discussing how the information you've already found doesn't address it should demonstrate that you're willing to do your part of the work. This is addressed in the READ THIS FIRST post.

If your comments have been edited for excessive quoting, you've probably gotten a warning about it from the moderators. Check your notifications.

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