"
Now, among the natural coloring matters, these "mordant dyes," as they
may be conveniently termed, are much more numerous than the "direct
dyes;" but be it observed, we have fast and fugitive colors in both
classes.
Referring first to the wool patterns and to the "direct dyes," we find
that the only really fast colors are Prussian blue and Vat indigo
blue. Turmeric, orchil, catechu, and indigo carmine are all extremely
fugitive.
As to the "mordant dyes," some yield fast colors with all the usual
mordants, e.g., madder, cochineal, lac dye, kermes, viz., reds with
tin and aluminum, claret browns with copper and chromium, and dull
violets with iron.
Other dyestuffs, like camwood, brazilwood, and their allies, also
young fustic, give always fugitive colors whatever mordant be
employed; others again, e.g., weld, old fustic, quercitron bark,
flavin, and Persian berries, give fast colors with some mordants and
fugitive colors with others; compare, for example, the fast olives of
the chromium, copper, and iron mordants with the fugitive yellows
given by aluminum and tin. A still more striking case is presented by
logwood, which gives a fast greenish-black with copper and very
fugitive colors with aluminum and tin.
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