Salt refers to any crystalline solid that is dissolvable in water—gold
chloride, for example. Each image is coated by hand, contact-printed in
the sun, toned in gold chloride, signed and waxed.

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The albumen process uses a bath of dozens of egg whites to coat the
paper as a binder for silver nitrate. Salt prints were often used as proofs
to show the client before creating final prints using the albumen process.
The albumen print was more desirable because of its silver burnished
quality, as seen in the Victorian carte de visite.