Howdy all,
           My experience with the term "clinker" refers in particular to 
the vitrified non-combustable waste left over from coal burning. If 
coal was not cleaned of all waste, such as clay, or contained shale or 
other types of rock inclusions, combustion would yield a melted 
metallic-looking ceramic. As a fire was fed, clinkers would grow and 
eventually cool the fire by preventing proper drafting and combustion. 
This definition comes from the railroad industry in those areas that 
used coal for fuel in steam locomotives. I do not have my references at 
my office right now, but could provide those to anyone who is 
interested. Thus, clinkers usually appear rather frothy, have a 
remarkably metallic sheen, and usually are produced in rather amorphous 
"globs" for lack of a better word. Coal ash is a different animal and 
depends on the type of coal being burned (bituminous or anthracite). 
Usually, coal ash will be a rather coarse yellowish/grey gravel-like 
consistency with a large degree of fine abrasive dust mixed in. If 
anyone would like a comparative sample of clinker or coal ash I could 
probably find or make some. Hope this is of some value.

 Regards,

 Stathi Pappas

 ______________________________________________________

 Efstathios I. Pappas, MS
 Doctoral Student
 Department of Anthropology/096
 University of Nevada, Reno
 Reno, NV 89557
 (775) 323-5730

 -----Original Message-----
 From: Timothy Scarlett <[log in to unmask]>
 To: [log in to unmask]
 Sent: Thu, 13 Oct 2005 17:28:16 -0400
 Subject: Re: clinkers, slag, etc.

 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
 >