Amberlith definitions

Amberlith

Another trade name for orange masking material.
Found on http://www.e-printing.co.uk/glossary.htm

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Amberlith

Red-orange acetate used for masking mechanicals when photographing for plates. The amberlith area appears black to the camera, and prints clear on the resulting film.
Found on https://www.encyclo.co.uk/local/22539

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