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This may just be the dumbest question ever asked . . . "How long does coal keep ?"

A little background: I've been learning a little blacksmithing for about a year now. I've found a local supplier that sells what seems to be good blacksmithing coal for $100 a ton. Smaller quantities are available at a higher price. The dealer is a large volume dealer and they normally sell by the semi-load. It is a big industrial facility and there are semi's and cranes and payloaders - back and forth. I have to drive way in the middle of all that. I've been lucky that they let me come in and fill my 5 gallon pails of coal for $3.50 each - which I still consider a good price.

I am worried that as this hobby develops that I may loose my coal source - either they stop carrying this type coal or for safety reasons they discontinue letting me inside with my little pails.

If I were to buy a larger quantity - is there any issue with storing it for a few years ? Maybe up to ten years. I realize that coal is a million years old - but does exposure to air or humidity and anything affect it? I would be storing it in covered garbage cans or something - not outside.

I told you it was a dumb question - but I don't want a ton of "bad coal" either.


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First of all, make sure it is good coal.

If it is, it will most likely outlast any of us. Really, it's just a rock. I don't think weather could hurt it at all.

Your only concern is keeping junk out of it that you don't want in your forge.

I find that leaves and an occasional hickory nut do no harm, but concrete dust and stuff like that are less than desirable.

So if it's good coal at a good price and you have the space for it, stock up. I'm afraid that it might only get harder to come by as time goes on.


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How long can coal be stored? Several hundred million years if stored properly.

Coal usually "goes bad"by having bad stiff get mixed into it---gravel, dirt, dust, etc. If you have a sealed storage facility the problem is usually only the degradation and failure of the holder---picking chunks of plastic out of your coal cause the garbage can rotted isn't a lot of fun.

Sealed as cats seem to like to poop in your coal; such an amusing smell when used...

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Coal can "spontaneously" combust. if stored in a large enough bulk quantity (multiple ton). Keep it dry, covered, and compacted. There was a thread regarding this posted several months ago with some articles on coal safety (and I can't find the thread or article).

Basically any time you have a fuel/air charge you have the potential to have a fire with enough heat. Under certain conditions (including dampness) coal will produce heat if it has enough air.


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Hey Hangman,

Coal does slowly oxidize when it is sitting around, the larger the chunks the slower the oxidation. Remember that the coal hasn't been sitting around outside for thousands of years, it was underground exposed to virtually no oxygen.

Having said that the coal won't loose any significant heat energy sitting around outside.

Coal spontaniously combusts when it is in a big deep pile and there is nothing to take away the heat developes inside the pile. Some of the large storage yards use pipes that circulate air through the pile to vent the heat or pipes with water running through them to cool the piles.

As long as its not deeper then you are tall you shouldnt' have any problem.

Really though, I would suggest that you ask the guys at the place that you buy it from the best way to store it.

Caleb Ramsby

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The following is quoted from "The Gas Engineers Handbook" by Henry O'Connor 1898. The gas referenced in the title is gas produced from wood or coal and used in furnaces, boilers etc. and for lighting.

"Coal when exposed to the air changes in character, the change consisting in a dimunition of agglomerating as well as of lighting power, and probably also of heating power.

The change is more rapid the higher the temperature and the more divided the coal.

In the small pieces the change in the character of the coal is greater on the surface than in the interior. In heaps of coal permeated by the air the change is greater in the centre then on the surface. When the air cannot penetrate to the centre the surface undergoes the greatest change.

Small coal washed is less liable to change then unwashed.

Large pieces of coal are only liable to change after a certain number of years' exposure o the air. The small coal is affected very quickly if it happens to be under conditions likely to raise its temperature.

In a few months it is capable of entirely losing its agglomerating and lighting power. Heaps of small coal become heated, but stacks of large coal do not heat to an appreciable degree.

Small coal should not be stacked in too large heaps.

Coal stacked in low heaps does not become heated. Heat increases with the height of the stack, and at about the height of 3 or 4 metres the temperature rises progressively and then descends without having exceeded 60 deg C. or 70 deg C.

The inner temperature of a stack 2 metres high does not usually exceed 40 deg C. to 50 deg C. (M. de Lachomette.)

Storing coal in the open may cause a loss of from 30 to 40 percent in the quantity of gas to be obtained from it.

North Wales coals and certain cannels are said not to depreciate appreciably through exposure when stored in the open, while certain Scotch coals have been known to lose 50 percent in value in 3 months.

All coals exposed to the air absorb oxygen, the volume of which may be 100 times that of the coal.

The loss and increase of weight are produced more slowly the larger the pieces of coal. (M. de Lachomette.)

The yield of gas from coal before exposure being equal o 26.36 fell to 6.60 after being subjected for 4 days to 400 deg C. and at 8 days nil. The illuminating power also diminished very quickly. (M. de Lachomette.)

Powdered coal containing from 1.6 o 8.3 percent oxygen when subjected to prolonged action of air and of stagnent and running water is not appreciably affected with regard to composition, yield of coke or calorific power. (M. de Lachomette.)

The drier the coal when stacked the less liability to heat, and all trampling or compression should be avoided.

The only thing to be done with heated coal is to open it out and allow it to cool, or the heating will spread.

M. Moring suggests connecting the two ends of a thin platinum wire, about .0008 inch diameter, laid through the thermometer to a battery and galvanometer, when the carrying resistance due to the rise and fall of mercury will be shown upon the galvonometer, and the temperature of anything may be observed at a distance, such as in a heap of coals.

Another form of indicator for showing when coals are heated above a certain temperature might be made by means of two wires from a battery covered with gutta-percha and the one wound round the other, so that when a sufficient heat was formed to melt the covering the two wires would be in contact, and could be made to ring an electric bell.

When large Stocks of Coke are stored in the open an increase in weight of 15 to 20 percent due to weather, has at times been found.

Stacking coke in large quantities deteriorates the quality.

100 lbs of coke can absorb 50 lbs of water.

Increased quantity of breeze due to use of coke breaker only about 5 percent of coke broken, or 1 cwt per ton of broken coke for sale. Less when broken while warm (say 1 1/2 bushel per ton.)

Oils flashing below 73 deg F are not allowed to be stored in warehouses or shops in England."

Hopefully some of you will find this information as fascinating as I do.

Caleb Ramsby

Edit: my T button is having issues and a few were left out. the spelling of the words in the quote are as printed in the book.

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In regard the 55's do you drill draingae holes in the bottom to dump any water? I have one and was going to use it outside for storage and was not sure about water accumulation. Currently I just stack 50 lb bags inside and dump them into a 20 gal galvy can near the forge.


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  • 3 years later...

i have the same problem but bigger where i live here in alberta our good smithing coal in 50 lbs bags is about $75 from home hardware they get it from ontaro but to get good coal from home here is hard because the suppliers woul let us buy it un less we get 100 tons or more i dont know how  if possible i could store this much  space is not an issue but a 100 tones how wuld you do that


i would use any ideas i could get


thanks eco

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I just open the small bung hole for drainage. In a plastic barrel I remove the water to just below the level of the coal. Dry coal on top to start the fire and damp / wet coal underneath to coke up.



If there was going to be a problem with storing coal outside, I figure this would be where it could start. The pile is now up to the bottom of the tower on the right, almost twice the coal shown. Under the Tower, notice the white pick up truck. I would saw there are several truck loads of coal there. (grin) The coal has been outside for two years or more at this point, in all kinds of weather.


This coal is for a power plant. It is sprayed with water to keep the dust down as it comes off the conveyor. Then the dozer moves it to form a mound of coal.



This is another pile of several tons of coal, outside in the elements. It is transferred to barges and shipped down river. Notice under the hump of coal on the right the raised bed of a 28 ton semi for comparison.



Another pile of coal. This pile will be reduced to half and then topped off again rather quickly It is loaded into rail cars for shipment by rail.  I have never seen it below about half of that amount shown. That means the coal on the bottom stays on the bottom.


And no they do not sell coal, I ask.

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I can only show you what I have seen. My little dab of coal was outside on a tarp to keep it separated from the dirt for several years, I put it into 55 gallon drums so I could use that area of the yard. Still have 10-15 drums left. If I was to do it again I would put plastic drum liners in the drums first. The coal and steel of the drum do not play well together, and it has eaten through a couple of the drums now. 



Photo from post #40 is copied here


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The coal and steel of the drum do not play well together, and it has eaten through a couple of the drums now. 




That's good to know. I've got a few steel drums I filled with coal for storage. I may try and talk to someone I know and see if I can't get him to let me have a few empty plastic ones if he doesn't have to return them when he empties them out.

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The plastic drums show no sign of degrading yet. A couple of the plastic drums are full of water. If I see skidders I just pour some oil on the top of the water. During the winter the drums freeze solid so keep at least a working supply dry and usable. (grin)


Usually nothing more than a hole in the bottom of the drum fixes both problems.

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Ok so it sounds like it's not so much the coal that is the issue, but water... That shouldn't be an issue since mine is all stored under the roof of the shed and should stay dry ( I have the drums up off the ground on 2x's to avoid moisture issues there) I wasn't sure if it was just something to do with coal itself causing the drums to rust faster. I know dampness and coke/ash in the forge seems to promote rust.

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Merry Almost,


Compost also gets hot from sitting outside.


I don't think there is any fear of your coal deteriorating from sitting. We get 50 ton at a time and it sits under a partial cover. Rain makes the fines go to the bottom. We mix the fines with water into a hardball size mud and add the hardballs to the sides of the fire like anything else.



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Out here the guild buys a truck load of coal at a time and stores it in a gated area outside I think there are wood floors to it but don't remember last time I scraped the bottom.  We get a load probably once a year.  7 dollars a five gallon is what good blacksmithing coal goes for in our guild.  pile is about as tall as me and we haven't had any issues with heat or degradation that I know of.  Each load can differ though as to how much sulfur or ash or clinker sand sorta stuff in it.  I store mine in a 55 gallon drum with no top and in some 5 gallon plastic pails with tops.  No problems with it.  I usually get 10 buckets about 2 - 3 times a year.   Amazing how much you can go through.  

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Yes water or even some moister in the air can make an acid that eats through the metal.  But till I can store it outside metal is the best I have been able to acquire for storing of my coal.  4 or 5 years going on and the bottom and sides have not rusted through on mine so I figure thats pretty good.  

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