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Charcoal Forge Fuel/Heat Management, etc...

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My Question (TLDR) - Whats the best method for Charcoal Forge Management and heat isolation in material?

My Forge:

Liam Hoffman inspired Firepot (5”x5” - 6” deep) with a tuyere and hair dryer blower. (See Pictures)

Just started blacksmithing for the first time last week and giving my homemade forge its maiden voyage. With the design as it stands and just starting out I decided charcoal would be the easiest, accessible fuel for me. Unfortunately, I’ve noticed there’s a lot more smiths who either use propane or coal forges in comparison, info seems a little harder to come by lurking around.

Is it best to heat stock, similarily to coal, in which you lay it across and pile charcoal over top? Should I size the charcoal smaller like 2”-3” or is there reasons to keep some of the large chunks for deeper in the fire? Do I control the heat tighter to the center using a spritzer of water on the outside pieces or easier to shrink the ID of my forge?

I’m working with 15mm Rebar, which I’ve cut to 2-1/2 foot lengths, to learn and practice on. Thinking I need to shorten them a bit to work on a little easier given the depth of my forge potentially.

(Will post photos when I’m on my computer... doesn’t like my phone)

Any information is good, I anticipate a lot will be just through experimentation but I hope to be doing this for a long time. You all seem to be full of useful info and very helpful!

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Welcome aboard Fey, glad to have you. If you put your general location in the header you'll find out how many members are within visiting distance. Every hour you spend working with an experienced smith is worth many times that figuring it out yourself. No kidding every hour is worth many hours even days working solo. Materials and supplies like smithing coal has a strong local aspect for example you can buy top quality blacksmithing coal in Pennsylvania by the ton for less than I can get it by the sack in Alaska. Have you looked in  the yellow pages and made a few phone calls? Try Farrier suppliers or a farrier.

Let's see, your questions. A bottom blast forge is designed to burn coal or coke efficiently, charcoal will burn up everything in or on the fire pot and be poor economically. It can be done but you have to fill most of the fire pot. There are details, illustrations and pics here somewhere. This has been discussed at length, hopefully someone will post a link. Save us both searching. You own a COAL forge.

Charcoal works MUCH better in a "Side Blast" forge which is a simple trench with the air blast introduced at a 90* in the center. There is a beautiful version originally posted by Charles Stevens and discussed at length here. "JABOD" (Just A Box Of Dirt" are good terms. It's an: easy, fast, cheap build not requiring great shop skills. A JABOD is easy to modify and  move, you can just dump the dirt in a couple buckets and it's light and easy to store out of the way. This type forge has been in regular use for at least 2,500 years LONGER than coal or bottom blast forges and they burn coal well. 

When you want to search something on Iforge use your preferred search engine and include "Iforge" in the search terms. The search engine provided with the forum OS is sucks pickles lousy.

Break the charcoal up to peanut size and use a very gentle air blast. A hair dryer is WAY TOO MUCH air, especially for charcoal. An easy way to control it is to aim it mostly away from the air supply pipe. Mattress inflator pumps are cheap at the big box stores and if you wait till the close out and clearance sales this fall REALLY CHEAP. They work really well with charcoal it will stay burning on it's own. Coal on the other hand needs air or it'll go out.

Glenn, the site owner has posted a beautiful illustration of a forge fire and how to place your work. I expect it'll show up shortly, I don't have the link handy. 

Anyway, No you don't lay your work ON the fire and pile fuel over it unless you've let your fire burn down that far. Working solid fuel I slip the work into the heart of the fire from one side and pay attention to it. You don't want to stare into a forge fire the IR radiation will eventually cause cataracts. Look frequently just don't stand there and stare, it's not like a campfire a forge fire is a much stronger ir radiator.

You isolate heat by only building a fire large enough to heat the desired area. How much air blast you apply is the strongest fire control method available to charcoal. No water on charcoal unless you want to extinguish the fire then just shovel it out and put it in a bucket of water. It'll dry out in a surprisingly short time and be just fine next time.  You need to spread it out to dry of course. Yes?

Rebar is NOT the best steel to use at the forge it's composition is not too consistent and you have to get rid of all those ridges. I HIGHLY recommend buying a 20' length of hot rolled steel at a steel supply. NOT a big box store like Home Depot  or the equivalent where ever you are. I like to start folks with 3/8" hot rolled square mild. or whatever low carbon steel is available there. 1/2" round is  close enough to the same mass per inch as to make no difference and is acceptable stock. A 20' stick won't cost more than two short pieces at a big box. Honest a full length is cheaper.

There will be folk with a lot more experience than I piping up shortly I'm sure. Well, maybe not too shortly it's an important holiday here, "Memorial Day" it's a day to remember and honor those who've passed, especially those who gave their lives in service to others, the military is front stage today. Things may be a little quiet on the forum today.

 Frosty The Lucky.


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Frosty covered it pretty well. I always suggest reading this to get the best out of the forum.  READ THIS FIRST  It is full of tips like editing your profile to show your location as so many answers require knowing where in the world you are located. There are many other tips, some will help in flying under the moderators radar.:) To post pictures you will need to resize them by 50% for the forum to allow the upload.

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Thanks to both of you, I really appreciate the time taken to give some support. Thank you Irondragon for directing me to the "Read Me" it's very useful Now that I'm here I'm hoping to contribute and peruse around, be an active member of IFI!

Just some pictures for reference to give some context:

1403242118_Forging2.jpg.60658e08c891bf5f2da7e071fa2b1b07.jpg      1914292938_Forging1.jpg.2a4da7c574a47f8641ddffb42fdfc686.jpg

63367593_Forge2.jpg.ddd74dac6759ccf1d8848012a02b1064.jpg     1408796095_Forge1.jpg.cba26b496fce031273ff1d05d2da6e78.jpg     Workspace.jpg.0a36745980bb232bcd6fcd384094e796.jpg

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With a boot on blast forge you need 2+ more inches of depth of fire pot and as Jerry pointed out it will eat you out of house and home.

The historical record shows a 3/4-1” ID tuyere producing a 6” heat zone. For myself I find a trench about 4” wide, 8” long and 4” deep works well, insert the tuyere into the bottom from the side of the trench at about a 5 deg. Angle. Then build up walls on each side of the trench 4” or more high and 8” or more long. The stock is placed into the fire at ground level ( the hearth) with fuel piled on top. This configuration will heat 1” bar. 

As to air, to much not only can blow fuel out of the fire pot it can actually cool the fire. Providing enough air to course the heart of the fire to reach the temperature  you want color and being patient and allowing the steel to soak is more fuel effencent than  heating the fire to white hot and risking burning the steel. Think roaring the perfect marshmallow where it’s golden brown and hot ant gooey in the middle, not burnt and cold...


I have fabricated a steel side blast fire pot to those dementions that works well with both coal and charcoal. 

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Putting your stock in at an angle is a perfect way to burn off the end, it should be almost horizontal and the fuel should mound several inches above it.  Why old blacksmithing commercial firepots have cutouts on the side to allow you  to get the workpiece lower down. The way that forge is designed you will have burning piece of charcoal dropping off the edges. OTOH you can build a trench out of clayey soil across the forge and firepot and get your trench fire. A section of angle iron across the ends will help act as a fence to keep fuel on the table.

Just remember that the viking era pattern welded swords were and the Japanese Katana are still forged in c harcoal forges. So if you are having problems; it's in your skills and forge design not the fuel!

(BTW when they talk of a air mattress inflater pump they mean one of the hand pumped ones not an electric one.)

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3 hours ago, ThomasPowers said:

The way that forge is designed you will have burning piece of charcoal dropping off the edges. OTOH you can build a trench out of clayey soil across the forge and firepot and get your trench fire. A section of angle iron across the ends will help act as a fence to keep fuel on the table.

So if you are having problems; it's in your skills and forge design not the fuel!

Hahah well I definitely think it’s skill mostly, it was only the first chance I’ve had to heat and beat steel! Which was great, I just knew from what I was experiencing there was something I had been missing and such why I’m here now.

My original design had intended to be more framed with the angle iron (With a notch front and back for laying stock across) but I had no understanding to why until afterwards seeing some of the coal forges being run. This is an easy enough mod which I intend to do.

I’m also going to procure some good coal from a nearby farrier supplier, this definitely seems more suited to coal, I’m sure I can figure out a way to mod to work better with charcoal, am glad I’ve got that direction now thanks to you all.

12 hours ago, Charles R. Stevens said:

As to air, to much not only can blow fuel out of the fire pot it can actually cool the fire. Providing enough air..... roaring the perfect marshmallow where it’s golden brown and hot ant gooey in the middle, not burnt and cold...

Definitely makes sense and probably why it felt like I had to dig deeper down since I was cooling higher with too much air flow. I have an air bleed hole in my supply line that I need to introduce a gate to reduce/redirect how much air is going through and hopefully having a better Fuel:Air ratio.

I also think I’m going to try your JABOD design, in the background of my forge you can see there’s a movable wooden crate which I think may work wonders. This way I’ll have a coal forge and a charcoal forge. 

*EDIT* Thought I should mention also I booked a blacksmithing 101 class at a local school in September which I’m looking forward to now! Thanks for the encouragement there.

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Everything as skill, all tools are is highly refined dirt and all they can do on their own is return to the soil. It's the clever monkeys with thumbs that do everything else. Don't sweat it, this is fun and none of us were born knowing this or heck any stuff. 

More than ONE forge!?!?:o <GASP!>

Welcome to the club.

 Frosty The Lucky.

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Not as bad as anvils and postvises, who could have only one! It would be like only having 4 dozen hammers!

I have dug a trench forge in the backyard before to do some forging that required a several foot long heat, no not a sword, a firebox for a Santa Maria replica. Lots of adobe Y1K forges; multiple gassers and my current coal travel forge, soon to be moved out for travelling in favor of the coal forge that came in the hoard. The RR forge awaits the carport to have some room to scare the neighbors...Postvises---5 mounted, 1 travel set up, 1 getting ready to be mounted under the carport and 3 leaning against the wall...(one Large, one Robust, one 200+ years old)


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Frosty I meant to ask for clarification on your charcoal sizing recommendation... When you mentioned "Peanut" sized is that shelled or unshelled, just for visualization sake, because shelled peanuts are relatively small (smaller than coal/coke generally should be or about the same?) For breaking up charcoal, what do you find the most efficient way, is it just best to crack it by hand or should I get a small centerpunch/screwdriver, I know it's pretty "flakey" so maybe just by hand is the best way to do it. I also want to then put it all in a solid container that I can easily dispense with a feed scoop or something into a steel pail for transport I think. Just brain machinations though. 

I KNOW right? multiple forges seems pretty extreme, and no amounts of convincing from you lot will sway me otherwise :lol: I'm gonna have a problem....

This is a safe space with no judgements right?!

Wow Thomas that's incredible, gotta say I'm jealous hahah, with almost unlimited possibility at my girlfriend's farm I imagine it won't help me with collecting stuff like you've got eh? Love seeing all the new and old stuff in a good home rather than rusting away in some junk pile, gives some purpose again!

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Shelled or not about peanut size is what I like. A blade works nicely you can just cut it up and minimize the flying bits and dust. It doesn't need to be like a kitchen knife, a short length of machete is perfect but a piece of sheet steel with a rough edge does nicely, hammer the far edge over for a handle and a wooden mallet or piece of wood to drive it through if you run into charcoal that doesn't cut easily. I've used an open can baked beans probably it was in camp doesn't matter so long as its a steel can. Yes?

The idea is to maximize surface area to volume of the fuel this maximized BTU output per cubic inch in the fireball and consume all the oxy before contacting your steel. Make sense? 

Much smaller than peanut and it can block the air, flame, heat flow too much not to mention blow out of the fire.  

The size you settle on will depend on what works best for you. Most of us who use solid fuel have our own style on top of the basics of fire. 

The bi thing to remember is Air controls the heat, you can have a huge pile of fuel and little heat but you can bring a handful of fuel to steal burning temps. More air burns the fuel faster meaning more BTUs per second released.

 Frosty The Lucky.


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I recently, (a little before the lockdown), bought a pile of old blacksmithing stuff that had been sitting in heaps on the floor of an old building.  Part of an all or nothing deal to get a few items I wanted.  I've been trying to sell off the other stuff; but lockdown makes that difficult; especially as I'm only selling "locally" for New Mexico values of Local.  (NM has little enough smithing stuff, I don't want to deplete things more!)   Last night I sold off a 5.75" Columbian postvise and a handful of set tools and tongs.  Loaded it up in the back of my truck and hauled it to the local truck stop to meet with a fellow who lived a couple of hours north.  Good lights so he could look everything over, (around 9:30 pm).

(Original "hoard")




Now I didn't get all of that; the owner wanted to keep some; after all they hadn't touched it in 25 years; but maybe tomorrow...I also bought the 3 powerhammers laying on old pallets in their side/back yard.

How, in a small rural town I had been living in for 16 years, did I find this?   TPAAAT!

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