Collectors' List No. 108 • 2004 Ice & Snow: Antarctica and Mt Everest

	NOTE: Linked large images in this collection have now been archived. If you would like to view images other than those thumbnailed here please contact us email.
Photographic Processes ...Carbon print: This photomechanical process, discovered by the French inventor Alphonse Louis Poitevin, is a close relative of the Woodbury type process, but does not usually have the same relief surface. Although both Woodbury types and carbon prints could have been made with any pigment then available, they were usually made in the colour that most closely resembled that of the photographs being reproduced - usually grey and black for carbon prints. Carbon prints may be more difficult to identify than Woodbury types. Under magnification there is no visible grain or half tone pattern of regularly spaced dots, but the surface may appear speckled with particles of pigment or dust. When viewed at an angle the surface appears glossy, more so in the shadows than in the highlights. They are regarded as extremely permanent. ...C-type print (chromogenic print): A chromogenic print is a colour print which is made from a colour transparency or negative in which the print material has at least three emulsion layers of silver salts. Each layer is sensitised to one of the three primary colours and records information about that colour makeup in the photograph. In the initial development a silver image is formed in each layer. With further development, dye couplers are added and when united with the silver, form dyes of the appropriate colours in the emulsion layers. When seen against the white print stock, the layers appear as a full-colour image. ...Contact print: The same size as its negative, the contact print is produced by placing the negative in direct contact with the paper rather than projecting the image onto the paper through an enlarger. Contact prints have extraordinary resolution, that is, sharpness of detail. All early photographs were made by contact printing, since successful enlarging became possible only in the 1890s. ...Silver gelatin photograph (gelatin silver print): This is a black-and-white photograph printed on paper coated with an emulsion consisting of gelatin and silver salts. The type of silver salt contained in the gelatin emulsion determines what method of printing is used. Papers containing silver chloride are used for contact printing, whereas papers containing silver bromide are used for enlargements. Chloro-bromide papers, which contain a combination of the two silver salts, may be used for either method of printing. The two silver salts also produce different tones in a print. The tone of a gelatin silver-bromide print is generally neutral black while a gelatin silver-chloride print is bluish-black or cool in tone. Prints on a chloro-bromide paper have a warm, brownish-black tone. ...Photogravure: The hand-pulled photogravure is one of the most beautiful ink processes for reproducing photographs. Alfred Stieglitz and other Photo-Secessionist photographs used it for illustration in the early photographic journal Camera Work. Photogravure is particularly suited to reproduce platinum prints and could be mistaken for platinum by the untrained eye. With some practice, however, gravures are easily identified. They are made with a copper plate which often leaves an indented or embossed plate mark around the image. Under magnification the image appears grainy, and dark areas and shadows appear pitted. The early hand-pulled gravures reproduced the continuous tone of an original photograph. Definitions of processes listed above were extracted and modified from a publication by AIPAD (Assoc. of International Photography Art Dealers, USA)