I said that Coalbrookdale had several air furnaces, rather than that they
had a double one. Foundries were often located in towns. My assumption is
that it was convenient to make the goods were the order was received rather
than at a remote location - at the blast furnace. My calculations in
respect of Coalbrookdale suggest that it was cheaper to make goods with iron
tapped straight from the blast furnace, so that the Upper Air Furnace
(probably near the Old blast furnace) was in use all the time; the New Air
Furnace only when a blast furnace was out of blast; and the Lower Air
Furnace was hardly used between 1724 and 1738.
As I understand it, commercial life in Virginia centred on stores on the sea
shore (including Chesapeake Bay), there being no towns. Accordingly, a
place on the shore (or a river bank) would occupy a similar commercial role
to an English town. Nevertheless, foundries were rare in England until at
least the late 18th century, when foundry cupolas began to be used instead
of air furnaces.
Peter King
49, Stourbridge Road,
Hagley,
Stourbridge
West Midlands
DY9 0QS
01562-720368
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-----Original Message-----
From: Arch-Metals Group [mailto:[log in to unmask]]On Behalf Of
James Brothers
Sent: 05 July 2008 18:59
To: [log in to unmask]
Subject: Re: Early Use of Coal in Foundries
Thanks, while I have seen pictures of air furnaces, I've never really
taken the time to look at operations and the chemical implications (if
any). Given that the fire and charge are separate it should have been
possible to use coal. And you have provided information on when the
British started using coal. Here in the colonies we had coal mines
from the early 1700s. So coal could have been used. but there was also
lots of wood to make charcoal. There was not the economic incentive.
So Coalbrookdale was operating double air furnaces? I wasn't aware of
that, but have not spent much time looking at foundry operations. I'd
gotten the impression that double air was used primarily for cannon.
The problem with Spotswood is twofold. While the population of
Virginia was growing, in the 1730s how much demand was there for cast
iron goods. And while it was certainly easier to transport pig, rather
than finished cast goods, the 20+ miles from the Tubal Ironworks to
Fredericksburg or Falmouth, VA (to get on the river) did it make
economic sense to build a double air furnace? This added the cost of
another furnace, more workers, and the cost of fuel. There were at the
time Massaponax was in operation at least six blast furnaces operating
in Tidewater and the near Piedmont of Virginia (Tubal, Bristol IW,
Fredericksville, Accokeek or Potomac, Chiswell's, and Neabsco.
Everyone else met demand by casting directly from the blast furnace.
If Spotswood has to remelt the pig, how is he competing? Or is he
doing something that requires large amounts of cast iron, like cannons?
On Jul 5, 2008, at 12:52 PM, Peter King wrote:
> In a reverberatory furnace, the fuel and metal are kept separate so
> that
> there is no reason not to use coal. The furnace is naturally
> aspirated, by
> convection in a tall chimney, so that no power is needed. It was an
> air
> furnace, as opposed to a blast furnace. My guess is that Spotswood
> had a
> double air furnace, because he wanted to produce a lot of cast iron
> goods,
> rather than large-sized cast iron goods. The Coalbrookdale Company
> had
> three in 1718-38, probably in different buildings, but only had one in
> constant use. A second was used when a blast furnace was out of
> blast, and
> the third hardly at all after the first few years of the period.
>
> Peter King
> 49, Stourbridge Road,
> Hagley,
> Stourbridge
> West Midlands
> DY9 0QS
> 01562-720368
> [log in to unmask]
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