WordWeb 3.03 based on a Princeton U., lexicon has an interesting
division of clinker, a noun and a verb (also used as a reed error,
i.e., on the clarinet, a squawk or squeak, ca. 1960's anyway)

Noun: clinker

1. A fragment of incombustible matter left after a wood or coal or
charcoal fire (synonym: cinder) Type of: entity fragment part piece
thing
2. A hard brick used as a paving stone (synonym: clinker brick) Type
of: artefact artifact brick building material ceramic entity
instrumentality instrumentation object  physical object unit whole
whole thing

Verb: clinker

1. Clear out the cinders and clinker from
      "we clinkered the fire frequently"
Type of: alter change clean out clear out empty modify

2. Turn to clinker or form clinker under excessive heat in burning
Type of: change


Noun: slag

1. The scum formed by oxidation at the surface of molten metals
(synonym: dross scoria) Types of: scum film object physical object
scum Types: basic slag
2. [Brit, offensive] (informal) a promiscuous woman (synonym: slapper
[Brit. offensive])
3. Stony waste matter, or material of similar appearance
        "a slag heap"

Oddly:

Noun: slag code

A delayed action computer virus; a set of instructions surreptitiously
inserted into a program that are designed to execute (or 'explode') if
a particular condition is satisfied; when exploded it may delete or
corrupt data, or print a spurious message, or have other harmful
effects (synonym: logic bomb) Type of: all things computer

followed by:

Noun: slagheap

1. Pile of waste matter from coal mining etc. Type of: all things
assemblage, i.e.. cumulus, aggregation, heap, pile, etc.

and last but not least

Verb: slag off
   Usage: Brit. vulgar
1. (informal) criticize, insult, talk down


There, however, inside the foundry around the foundry floor, another
group of terms, for example, reported by Edward Rutsch, et al, in the
West Point Foundry, Cold Spring, NY research, which provided a list of
terms that had no apparent connection to the objects being created, a
specialists language perhaps, these people brought from Europe and
Great Britain under clandestine design, the exportation of "national
knowledge" pertaining to that industry against the law in England at
least if not in other countries at the time. Foundries, like
glasshouses, perhaps, as a trade, had their own parlance or idiom
ontop of a regional dialect, i.e., Scottish, Welsh, Gaelic, etc.

George Myers