A colloidal, lusterless, fine-grained, earthy
substance which generally develops plasticity when
wetted but is permanently hard when fired.
Chemically clays are aluminosilicates, which do
not form large crystals. The finely divided
aluminosilicates, which are responsible for the
properties associated with clays, are called "clay
minerals." Clays with a preponderance of the clay
mineral "kaolinite" are used both as fillers and
as coating pigments in the manufacture of paper.
Other clays are used in small amounts. Used in
excess, as it is in some art papers, clay becomes
an adulterant to the detriment of the strength and
durability of paper. See also: ATTAPULGITE CLAY ;BENTONITE ; KAOLlN;
PAPER CLAY .
(17 , 235 , 343 )