Other things being equal, those artificial ultramarines are most durable

which possess the most colour; and all are, perhaps, most permanent in

water. If used in that vehicle, care should be taken to employ a gum

free from acid; also, whether in water or oil, not to compound the blue

with a pigment which may possibly contain acid, such as constant white.

Acid, as we have said, is the great test for ultramarine; whence if a

sample be sophisticated with cobalt, its blue colour will not be

entirely destroyed. With high-class artistic pigments, however,

adulteration is the exception and not the rule. It is as a powder-blue

for the washtub that ultramarine gets disguised, when it is ground up

with soda-ash, chalk, gypsum, &c., and sold sometimes under its own

name, but more frequently as superfine Saxon smalts.


Coeruleum Of Pliny Were A Blue Copper Earth However That May Be In Colour Also May Comprise A Similar Series Of Hues Between The Extremes facebooktwittergoogle_plusredditpinterestlinkedinmail