Coal Forge : "Best" size for coal pieces : is there one?

Fire building / starting up a coal fire, is often discussed, but I've never heard anyone comment on the actual size of the coal "lumps" used.
I never really pay much attention to it, I just take a bucket full and dump it on the fire :)
But is there any reason to prefer large coals or small coals?
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John Fly wrote:

There may be a reason to prefer one or the other, but in the scheme of things, it's use what you can get.
I learned coal fires using fines and screenings. It was what was available.
I gotta say that the first time you start setting up to make a coal fire, in front of somebody new, by pouring a couple scoops of loose coal on the table of the forge and dumping a couple cans of water on it and mixing it into black mud.... Well, They look at you kinda funny!
Cheers Trevor Jones
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Trevor - I cant disagree that we have to live with what we can get, but...
In an ideal world <g>, what would be best?
As a complete newbie who has yet to start his first fire or buy his first bag of coal, it would be good to know what I'm REALLY looking for, even if I have to settle for 'anything that burns'!
Jay
Trevor Jones wrote:

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JayBee wrote:

Personally, I like it fairly uniform, and maybe about 3/4 of an inch across or so. Recently, I've been using the black mud with occasional boulders. It's a pain, but it does burn.
- ken
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Pocahontas #3 is a good metalurgical grade coal. It is used, in larger sizes (3 inch or so) in steam boilers. We used to get it from a yard that sold it for that steam boiler purpose. Once the bunker was down to about 2 feet deep, that became the "blacksmith coal", since it was mostly smaller pieces.
Find a blacksmith club close to you and ask them where they get theirs. Our club buys 20+ tons at a time and resells it to members.
Pete Sanaitis
You want a coal high in BTU content and low in ash and other impurities.
JayBee wrote:

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JayBee wrote:

Have you actually tried to find a supplier that has a selection (or any) metalurgical coal? Like good steam coal, it was once common, but now is not. In an ideal world, we would be picky. In our present world, picky means doing without. What you are REALLY looking for is coal. Coal suitable for smithing, preffered, size optional.
If you find a supplier that has any coal at all, ask if they know the composition. Chances are beyond likely, that they will look back at you like you are thick, and repeat to you that it contains coal. In the unlikely event that they actually know it's composition, low ash content and low sulphur are preferred. There are ratings for BTU/pound, but outside of the odd mention in live steam circles, I've not seen them used.
You can also forge with charcoal, and I have read of guys using green oak, broken into fairly fine chunks as fuel.
From my view, use what can be got. Chunks can be broken to fines, and fines can be mixed with water and coked into large chunks if required.
I have managed to forge weld with some truly poor quality coal (shoveled off a pile at a lime plant) that required a coordinated effort between the cranking of the blower and the fishing of large chunks of clinker from the firepot whilst loading more fuel into the fire pretty much simultaneously. I estimated at the time that I got about half as much clinker out of the fire as I put in coal. It's less stressful to use nice clean hot burning coal, but that was what was there.
Cheers Trevor Jones
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I'd say that thumb sized pieces of coal are about the largest that you want, with some finer stuff. That makes it easier to mound up and shape the fire. Also, I think the smaller stuff makes coke that is more compact.
Pete Stanaitis --------------------
John Fly wrote:

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Well...it depends on what you are trying to do. normally I prefer fines because with a piece of 2x4 lumber I can form fines into an oven for welding or heat treating by packing fines around it. And if I had a choice I'd take the fines every time. Reason? I can forge with fines but I can't make an oven with lump coal. Plus I think the burn rate of fines is a bit slower because the flames can't whistle through the gaps and expand so quickly.
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