Panchromatic film is sensitive to all colours and can only be handled in total darkness.
Screenprinting and etching photo-emulsions fall into this category and may be handled safely under yellow safelight conditions. Screen and etching photo-emulsions may also be safely handled for short periods of time under low levels of artificial light or very low levels of natural light, although this is not recommended. The salt is dissolved in water after the plate has cooled. Also used to remove the burr formed during line engraving. Also available in synthetic materials.