Developers, toning solutions and dyes should be mixed in crocks of
glazed earthenware or enameled iron, using warm water where necessary
and ensuring thorough solution by stirring with a wooden paddle,
which should be thoroughly washed after each operation. Having
thus dissolved the chemicals in as small a quantity of warm water
as possible, filter through fine muslin and make up the bath with
cold water, so that the final solution will be at approximately the
correct temperature.
The chemicals employed should be pure (for the samples, “EKCo.”
tested chemicals were used), and in cases where a good water supply
is not available, only distilled water should be used.