Blue pigments and dyes are rare in nature and consequently blue colorants are precious commodities in the pre-RoF world. Some are minerals, some are plant or animal extracts, and a few are synthetic in nature.

A colorant must be incorporatable into the intended substrate, and it should be resistant to environmental conditions (light, heat, water, acids, alkalis) that might degrade or remove it. And of course it should be nontoxic, easy to produce in quantity, and inexpensive.

Bear in mind that nowadays colorants are . . .

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- The Grantville Gazette Staff