SELECTED PHOTOGRAPHIC PROCESSES
Identification: Most popular photographic process from 1855 to 1890's. Paperbacking is extremely thin and breaks or cracks easily. Often shows signs of fading, with yellow highlights or a reddish-brown tone.
Storage and conservation: Avoid touching the surface. Place images individually in neutral pH paper or inert plastic enclosures and store them upright in acid-free boxes.
TYPE: Collodion emulsion photographs
Identification: Common from 1848 to 1880's. Varieties include ambrotypes, tintypes, wet plate negatives, and wet plate positives.
Ambrotypes (1854-1870's) were made of glass, sometimes coloured, often with black velvet backing and elaborate cases.
Tintypes (1854-1900's) were made of iron, japanned black or, after 1870, chocolate coloured.
Storage and conservation: Do not remove photographs from cases except for brief periods, to clean or replace backing. Do not try to straighten out bent tintypes. Dust tintypes with a soft brush or air bulb but do not wash. Wrap photographs individually in neutral pH paper or inert plastic enclosures; store vertically.
Identification: Coloured image rather than black and white. Popular after 1930's. Produced using a colour-separation process requiring a more complicated chemical process than black and white.
Storage and conservation: Colour prints and negatives have a short life span compared with black and white; copy valuable images onto black and white film. Keep away from bright light; place face down if not being used or stored. Store individually or in groups in neutral pH paper or inert plastic envelopes or folders.
Identification: Common from 1839 to 1860's. Made of copper, silver-plated. Silver tone before 1841-42, brown tone after. Images may appear either as a positive or negative, depending on how light falls on it.
Storage and conservation: Extremely fragile and often highly valuable. Never touch surface. Do not remove from case. If the glass is broken or damaged, have a conservator repair it. Wipe case clean with a damp cloth and store photograph upright in neutral pH paper or inert plastic enclosure in an acid-free box cut to fit the photograph snugly. Can be difficult to copy because of reflection from glass surface; allow up to 50 per cent increase in development time.
Identification: 1885 to present. Black and white prints and negatives. Common photographic process today. Paper might be rag-based or resin coated.
Storage and conservation: Particularly susceptible to curling; can be straightened by dampening the backs and placing the image between clean, white photographic blotting paper unti I dry. Do not try to flatten by pressure only, or the emulsion might crack. Store individually or in small groups in neutral pH paper or inert plastic envelopes or folders which give rigid and inflexible support.
Identification: Popular from 1 850's to 1 920's. Rare today. Glass base, with a reversed image. Plates with thick glass and ground edges produced with a collodion process; thin plates with sharp edges produced with a gelatin dry plate technique.
Storage and conservation: Store in individual folders or envelopes on edge in metal file drawers with supports on either side to keep items from moving or breaking. If possible, store each image in a padded container (such as bubblepack). Allow enough space in between each plate to permit air to circulate, but keep plates close together to prevent moving or slipping. Copy valuable items.
Identification: Reversed image. Come in rolls or strips as well as individual sheet film.
Storage and conservation: Cut rolls into individual strips, identifying each image and its original location on the roll. Avoid touching the emulsion (dull) side, handling negatives by the edges or non-emulsion side instead. Do not cut 35 mm or smaller strips of film into single images. Make prints of all negatives. Store negatives individually or in groups in neutral pH paper or inert plastic envelopes or folders. Identify nitrate-based film (look forword "safety" or edge or burn a small piece; if it burns quickly and thoroughly it is nitrate-based). Store nitrate film separately, in a container allowing plenty of air circulation. Copy it as soon as possible.
TYPE: Toned and coloured prints
Identification. Toning is a process used on a variety of different photographic types. Sepia toned prints have a yellowish or light brown colour; they were often mounted on boards. Photographs were also gold toned and hand coloured. Usually taken by a professional photographer.
Storage and conservation: Store individually in neutral pH paper or inert plastic envelopes or folders. Never exhibit originals.
Identification: Transparent images, usually 35 mm, mounted in plastic or cardboard containers.
Storage and conservation; Store in neutral pH paper or inert plastic mounts or in metal slide cabinets or trays; copy originals if possible. Keep slides exposed to air. Avoid projecting originals; if done, warm up projector first to prevent heat or light damage to the slide.
Identification: Popular from 1850's to 1920's. A pair of identical photographic prints mounted next to each other on a card, usually about 3 1/2" x 7". Early cards were flat, and later cards had a curve in them. They were examined through a viewer.
Storage and conservation: Store individually in neutral pH paper or inert plastic enclosures in acid-free boxes cutto size. Do not try to straighten curved images. Do not try to clean or repair dirty images unless you have proper facilities.