copy of Dipsacus, orotone

Orotone or silvertone is a photographic process dating from the late 19th century. It involves making a positive print on a glass plate, which has been previously sensitized with a liquid silver gelatin-bromide emulsion. The plate is developed from a silver negative under an enlarger or by contact with a countertype. After exposure, development and drying, the back of the glass plate containing the emulsion is coated with a gold or silver varnish, or sometimes even gold leaf. This varnish then shows through on the lighter parts of the print in the highlights. This process brings unequalled luminosity and depth. Orotone or goldtone was used by Edward. S. Curtis in his portraits of Native Americans