Coal in the Bunker

[caldrail]

Since my day on the Marlborough Downs I've been delving into the local records for Roman period trivia concerning that area, and I've turned up a suprise. In four sites in North Wiltshire, the remains of bitumous coal have been found dated to that period.

 

Now it's thought the Romans mined coal in Benwell, Northumberland, but that's a heck of a long way to get it, two hundred miles or more. Sources closer to home might be the Forest of Dean or Somerset, but as far as I know there's no indentifiable Roman period coal mining there.

 

The strange thing is why they needed it. The Downs weren't short of timber back then, and indeed, english villas are thought to had their homes heated from wood burning furnaces. Now if they went to the trouble of mioning and transporting this stuff, they did so for a reason. I must admit, apart from the obvious (and superfluous) use of burning for heating homes, what else could coal be used for.

 

I have thought that perhaps the coal was used for a specialist purpose, such as forgework or such, but does coal have any significant advantage there?

[Maladict]

Lead-smelting, drying of grasses/grains, ironworking?

As it seems to be a British thing, I'm going with drying

 

Coal: A Human History

by Barbara Freese

 

Coal has been both lauded for its efficiency as a heating fuel and maligned for the lung-wrenching black smoke it gives off. In her first book, Freese, an assistant attorney general of Minnesota (where she helps enforce environmental laws), offers an exquisite chronicle of the rise and fall of this bituminous black mineral. Both the Romans and the Chinese used coal ornamentally long before they discovered its flammable properties. Once its use as a heating source was discovered in early Roman Britain, coal replaced wood as Britain's primary energy source. The jet-black mineral spurred the Industrial Revolution and inspired the invention of the steam engine and the railway. Freese narrates the discovery of coal in the colonies, the development of the first U.S. coal town, Pittsburgh, and the history of coal in China. Despite its allure as a cheap and warm energy source, coal carries a high environmental cost. Burning it produces sulfur dioxide and carbon dioxide in such quantities that, during the Clinton administration, the EPA targeted coal-burning power plants as the single worst air polluters. Using EPA studies, Freese shows that coal emissions kill about 30,000 people a year, causing nearly as many deaths as traffic accidents and more than homicides and AIDS. The author contends that alternate energy sources must be found to ensure a healthier environment for future generations. Part history and part environmental argument, Freese's elegant book teaches an important lesson about the interdependence of humans and their natural environment both for good and ill throughout history.

 

I wonder what kind of data this is based on.

[Melvadius]

I have thought that perhaps the coal was used for a specialist purpose, such as forgework or such, but does coal have any significant advantage there?

 

Coal is generally not used directly for metal working as the most common type (bitumous coal) releases sulpher and other impurities into the metal being worked. It is much more common when forging metal to work with coke (which is produced by cooking coal under low oxygen conditions) although wood was also used historically. That isn't to say that coal may not have been used in some circumstances just that its direct use is less likely.

 

As coal, and even more so coke, burns hotter than wood it makes working metal easier however it also requires improved chimneys with better insulation to stop the transfer of heat and consequent increased risk of fires breaking out in thatch or other combustible material.

 

As far as I know the main discoveries of coal use in the Roman period have been associated with domestic and some religious sites - possibly linked to sacred flames but at least one instance is on record of coal being used to dry corn. As Roman corn drying kilns used indirect heat the corn would not have been affected by impurities carried in the smoke.

 

NB because of this release of impurities the increasing use of coal for cooking in the Victorian era, rather than over wood fires, was a key factor in the development of cooking ranges which utlised indirect cooking methods.

 

Melvadius

[Lost_Warrior]

Coal is generally not used directly for metal working as the most common type (bitumous coal) releases sulpher and other impurities into the metal being worked. It is much more common when forging metal to work with coke (which is produced by cooking coal under low oxygen conditions) although wood was also used historically. That isn't to say that coal may not have been used in some circumstances just that its direct use is less likely.

 

I would say it was used for metal working. Coke is produced in a forge by burning coal- I have forged iron with 'fresh' coal and also with a good bit of the coke that tends to build up in the fire- yes, until the coal burns down into at least some coke, you have a big, smokey, sulfuric mess. (A good smith will tend the fire in a way that encourages the buildup of coke.) The first coal fire of the morning is a "light and run" sort of deal...that is, at least if you had the kind of crap chimney I worked with. (Fresh coal is routinely added to the fire a little bit at a time to keep it burning once it gets going as well.) Coal, and better yet, coke, is the best material that the Romans likely had to forge weld- you need a VERY hot fire to do that- one that's easily achieved with coal and coke and not so easily achieved with wood and charcoal.

 

Just don't breathe the yellow smoke mmkay? There will be a lot of yellow smoke.

 

I would never personally recommend building a smithy with a thatched roof...the most fireproof materials available are recommended.

Edited April 7, 2009 by Lost_Warrior

[Melvadius]

I would never personally recommend building a smithy with a thatched roof...the most fireproof materials available are recommended.

 

True but not always so in 'traditional' English construction. To adapt a quote from a British TV comedy show 'Red sky at night could mean the forge is on fire again' .

 

This is not to say that thatch was commonly used but that either a very solid chimney and/or some other means of separating the flamible material from the heat source usually has to be considered when working metal. Traditionally in England some forges were initiallly situated in smaller 'out' buildings away from larger and more important structures and/or a stone or tile roof would be used (as the Romans tended to do) with solid timber supports which would take time to burn.

 

This is one of the advantages of using solid oak timbers as a building material. It is slow to catch light and even with intense heat often slowly chars rather than burns usually giving people a chance to fire fight before needing to escape.

 

Melvadius

[Lost_Warrior]

The one I apprenticed under told me that every smith burns down at least one shop in his lifetime.

[sylla]

There's both textual (mostly the Elder Pliny) and archaeological (mostly British) evidence of some extraction and a discrete trade of coal. Its use as fuel was always secondary and far from charcoal and wood in Rome and elsewhere, at least up to the Southern Song dynasty in China. Roman metallurgy added coal to some alloys; it was also used for jewelry, cosmetics and medicine.

[Maty]

Wandering outside my area of expertise once more ...With weaponry I'd assume you can use coal to make the original 'bloom' for smelting the iron from the ore, as the ore is in a container and will not therefore directly absorb sulphur and the high temperatures obtainable with coal make it very cost-effective. Obviously you need charcoal for the steel-making part as you need carbon from the charcoal, and definitely not contaminants from the coal.

 

How about baking bricks and roof tiles? It assume this can be done with wood, but more effectively with coal.

[Lost_Warrior]

I'm not sure. I think coal might get TOO hot for bricks and roof tiles. At least, I've never heard of anyone using something other than wood (or in modern times, gas) for that purpose.