Great question Marty!
I have semi-conscientiously used slag to refer to both metal smelting
waste from both blast furnace and bloomery furnace production, as
well as the waste from coal burning. I often modify the latter term
with "coal slag" while iron production slag is merely "slag." I know
that many people use the term clinker to refer to coal ash and
reserve the term "scale" for ash, carbonized bone, and other junk
from wood fires. I've pulled down my handy copy of Chambers'
Dictionary of Science and Technology (1999). It looks like, at least
as far as the engineers are concerned, Clinker is the preferred term
for coal burning waste and Slag for metal production waste. I don't
particularly care for their definition of Klinker Brick, since many
builders and archaeologists use the term "Clinker brick" to refer to
over-fired and warped brick from the heart of a clamp or updraft kiln
which are deformed during manufacture. They are often used inside of
walls, but not showing on a wall's surface, where better bricks were
used (Except during the Arts and Crafts movement). I have not come
across a term yet for the overfired, glazed, vitrified, and runny
mess that forms on the brick surface in a kiln or furnace. I'd like
to hear what others think. I've honestly come to call the stuff
"goop" because I don't want to apply an incorrect term.
pages 1061:
Slag (Engineering) The top layer of the two-layer melt formed during
smelting and refining operations. In smelting it contains the gangue
minerals and the flux; in refining, the oxidized impurities. See
figure at Blast Furnace.
Slag Cement (Civil Engineering) An artificial cement made by
granulating slag from blast furnaces by chilling it in water and then
grinding it with lime, to which it imparts hydraulic properties.
Slag Wool (Engineering) Fibrous material very similar to fiber glass
but made from slag produced by an iron blast furnace as distinct from
silicate glass.
page 219:
Clinker (Engineering) Incombustible residue, consisting of fused ash,
raked out from coal- or coke-fired furnaces; used for road-making and
as aggregate for concrete. See Breeze Block.
Clinkers (Building) See Klinker Brick
p. 647
Klinker Brick (Building) A very hard type of brick much used in
Holland and Germany, principally for paving purposes.
Cheers,
Tim
On Oct 13, 2005, at 3:23 PM, Marty Pickands wrote:
> I have always thought of the term "slag" as referring simply to
> something that has melted and congealed. Thus, it could mean the
> liquid waste resulting from some reductive process such as
> smelting, the bubbly looking cinder from burning coal, the
> discarded residue from glass production, the glassy material
> coating the inside of a stoneware kiln, or even melted glass or
> metal from a house fire.
>
> Going over the Histarch archive references to slag, however, forced
> me to realize that my definition was not the accepted one, so I
> looked up the word in several online dictionaries and in Webster's
> Unabridged. The definitions all agreed that the term applied to the
> liquid byproducts of smelting metals, and a couple also applied it
> to the non-combustible residue from the incomplete combustion of
> coal. One mentioned extremely burned brick under the term.
> "Clinker" appears to be a partial synonym referring to the glosssy,
> bubbly form. "Cinder" is given as referring to the products of
> incomplete combustion, including coal clinker.
>
> However, it still seems to me that the thick glassy stuff from the
> inside of a kiln, glass manufacture waste and melted glass and
> metal should all come under the term "slag" as well. With the
> exception of the melted glass and metal, I am not sure what other
> term can be used to describe them. I decided to see what the rest
> of you think about the definitions of these words in an
> archaeological context.
>
> Marty Pickands
> New York State Museum Cultural Resource Survey
>
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