-----Original Message-----
From: HARVEY DAVID ... COLLECTIONS <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Monday, May 03, 1999 9:24 AM
Subject: RE: Carbon-14 Dating of Iron
Mr. Harvey's remarks about the Ohio pit furnaces in this posting reflect a
misunderstanding, I believe, of evidence contained in my web site, or
perhaps erroneous information he received at the Iron Masters meeting. Also,
it seems
that I had company in being unaware of positive developments in the
dating of iron which have emerged lately in arch-metals.
>A few points in response to William Conner's posting:
>
>I believe that the point that Martha Goodway was making referred to the age
of the forests being harvested in the United States into the 19th century
A.D.. Carbon-14 accumulates during the life span of an organic organism and
the dating methodology will, of necessity, reflect this. You are not dating
as to when the charcoal was made, but rather when the tree had significant
levels of C-14 in its early life. This, I believe was the point that Martha
was making.
>
>There have been significant refinements in the application, methodology,
and interpretation of C-14 since 1969. I am sure that many others on the
list can articulate those issues better than I.
>
>As to the use of green wood in an actual furnace itself I think that makes
an already difficult metallurgical process almost impossible to achieve. The
use of green wood, it seems to me, was probably in the charcoal making
process itself and quite distinct from the operation of the furnace. Copice
harvesting in the management of forest resources is an excellent example of
this. In iron smelting you require reduction, high temperatures, and a light
fuel source so that gasses (notably CO) will readily filter through the
>charge.
It now seems the use of green wood was only to make charcoal for a furnace.
I have noted a number of technical errors in several books of American
history in passages devoted to early American iron furnaces. The use of
green wood as furnace fuel is apparently one such error.
>
>As to those Ohio Pit furnaces. I recently saw a presentation on them by a
>colleague of Mr. Conner at the Iron Masters meeting.
I was unaware of this presentation and whoever gave it was not a colleague
of mine. My web site must have served as the sole basis for it.
I recall an e-mail from some fellow last November who informed me about the
upcoming Iron Masters meeting and suggested I submit a paper to the
conference. Perhaps this is the person who gave this presentation.
(This e-mail was accidentally deleted when I had problems with my new
computer).
>Yes, they represent
some sort of pryo-technological process. However, I remain unconvinced that
they represent bloomery furnaces. The presence of green "slag" on red bricks
means nothing. Those are common brick artifacts also found in pottery kilns,
glass furnaces, and brick kiln remains - especially where salt was added to
provide a glazing effect. The furnaces have a very broad diameter and are
shallow, a brick air-slot comes into the very bottom of the pit and looks
much more like an air vent for a kiln than a tuyere location in a furnace
>wall.
This is a mistaken impression of the Ohio pit furnaces.
Photos of the furnaces are views of their remains as excavated. The Lynn
Acres furnace, for example, had already lost part of its upper wall and
contents
when the land owner's bulldozer cut it off while constructing a farm pond.
But these furnaces, as confirmed by our excavation of the Lynn Acre site,
were bowls, typically deeper than wide. A careful reading of material in
my web site should have revealed to Mr. Harvey that the blast was achieved
through the use of an air duct and a hearth matrix of stones. Instead of a
single tuyere, or two or three, these furnaces utilized the blast from
multiple tuyeres!
>These design features would inhibit direct-process ironmaking. The
presence of bog ore in a fire-reddened pit means nothing. Bog ore had uses
other than for iron making, notably in Colonial America for making
iron-oxide slips for pottery. The same mistaken interpretation of a kiln for
an iron furnace was ma!
> de!
> in the 1950's during the excavations of Jamestown Island, Virginia by the
National Park Service. Slag is produced in many pryo-technological
processes. Microscopic and petrological examination of specimens can be
important evidence in identifying the process that created the slag.
>
>Cheers!
>Dave
>
>David Harvey
>Metals & Arms Conservator
>Williamsburg, Virginia USA
>
>
>
Did we mistake Ohio pit furnaces for brick or pottery kilns? No, I believe
we certainly did not. A very basic reason why these pits are unsuited for
brick or pottery is that the pits have nearly vertical walls which descend
to rounded
bottoms. There's simply no evidence of a level surface in them to stack
greenware! Also,
there is no broken pottery or broken glass to suggest these uses. And,
bricks were made in early times in Ohio in "scove kilns" which consisted of
green bricks stacked up on cleared, level ground to form a kiln in which
spaces were left for the fire and distribution of the heat. Many 19th
century
brick farm houses in the Ohio pit furnace area were made on the farm in such
kilns by
traveling brick makers.
The glazes on materials from the Ohio pit furnaces have been examined by
professors of metallurgy and ceramics of Ohio State University. They say
these are iron glazes produced at temperatures consistent with the
production of wrought iron by the direct process. The professor of
metallurgy told David Orr and I he was certain our Lynn Acres pit furnace
was used as an iron smelter after viewing our photos and examining our
artifacts.
And, a respected historian of metallurgy, Leslie Aitchison, told me in 1970,
judging only by color
photographs and a written description, that the Ohio pit furnace in question
was almost certainly an iron furnace. As a journalist, I had sought
Aitchison's advice so I could decide whether or not to write news stories
about them. Again, this is mentioned in my web site. Also, I still have
Aitchison's hand written letters to me and am willing to share their
contents with anyone who is interested.
William D. Conner
908 S. Roys Avenue, Columbus, Ohio 43204
Phone: 614-276-5219; e-mail: <[log in to unmask]>
web site: America's Mysterious Furnaces
<www.iwaynet.net/~wdc>
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