, one which becomes dry by evaporation or oxidation.
The objector article to which such paint or varnish or wash is applied
is itself rendered visible in the darkest place, and more or less
capable of imparting light to other objects, so as to render them
visible also. The phosphorescent substance found most suitable for the
purpose is a compound obtained by simply heating together a mixture
of lime and sulphur, or carbonate of lime and sulphur, or some of the
various substances containing in themselves both lime and sulphur--such,
for example, as alabaster, gypsum, and the like--with carbon or other
agent to remove a portion of the oxygen contained in them, or by heating
lime or carbonate of lime in a gas or vapor containing sulphur.
The vehicle to be used for the luminous paint must be one which will dry
by evaporation or oxidation, in order that the paint may not become soft
or fluid by heat or be liable to be easily rubbed off by accident or use
from the articles to which it has been applied. It may be any of the
vehicles commonly used in oil-painting or any of those commonly used in
what is known as "distemper" painting or whitewashing, according to the
place or purpose in or for which the paint is to be used.
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