4. Wool fibre as in No. 2, with dye deposited on surface of
proof.
5. Section of proofed and veneered body, showing unproofed
surface.
6. Section of proofed body without "veneer."]
LECTURE VIII
MORDANTS: THEIR NATURE AND USE
The name or word "mordant" indicates the empiricism, or our old friend
"the rule of thumb," of the age in which it was first created and used.
It serves as a landmark of that age, which, by the way, needed
landmarks, for it was an age of something between scientific twilight
and absolute darkness. _Morder_ in French, derived from the Latin
_mordere_, means "to bite," and formerly the users of mordants in dyeing
and printing believed their action to be merely a mechanical action,
that is, that they exerted a biting or corroding influence, serving to
open the pores of the fabrics, and thus to give more ready ingress to
the colour or dye.
Most mordants are salts, or bodies resembling salts, and hence we must
commence our study of mordants by a consideration of the nature of
salts.
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