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