Aid to identification of the most common black and white historical photographic process and supports
|Type of process||Date of invention/Introduction (Period of greatest popularity)||Image||Emulsion (if any)||Support||Typical Presentation: Loose (L), Mounted (M), Case (C), Framed (F), Albums (A)||Identification|
|Daguerrotype||1839 (-1850's)||Silver and silver/mercury amalgam||-||Silver coated copper Plate||C/F||Unique. Negative/positive image in raking light.|
|Photogenic Drawing||1834/1839 (1840's)||Silver (POP)||-||Paper||L||Paper fibres visible. Sepia - lilac brown.|
|Salted Paper Print||1839 (1840's-1850's)||Silver (POP)||-||Paper||L/M/A||Paper fibres visible. Sepia - reddish brown.|
|Calotype Print||1841 (1840's-1851)||Silver (physically developed)||-||Paper||L/M/A||Paper fibres visible. Sepia, but more contrast than above.|
|Waxed Paper Calotype Negative||1841 (1840's-1851)||Silver (physically developed)||-||Paper||L||Waxed and traslucent.|
|Cyanotype||1842 (1840's & 1880's-1890's)||Iron compounds||-||Paper||L/A||Paper fibres visible. Blue colour.|
|Wet Collodion Negative||1851 (-1870's)||Silver (physically developed)||Collodion||Glass||L||Hand-coated, fingermarks in emulsion and varnish at corners of plate. May be creamy colour in dark areas.|
|Collodion Positive||1852 (-1880's)||Silver (physically developed)||Collodion||Glass||L/F||Unique. No negative/positive image in raking light. Black backing or ruby glass.|
|Tintype||1856 (-1930's)||Silver (physically developed)||Collodion||Iron||L/C/F/A (Card folders)||Cased tintypes - test with magnets over cover glass - magnetic field.|
|Albumen||1850 (-1890's)||Silver (POP)||Albumen||Paper||L/M/F/A||Usually finely crazed emulsion. Yellowish sepia. Thin paper base. Tendency to curl.|
|Collodio-Chloride||1864 (1880's-1910's)||Silver (POP)||Collodion||Paper||L/M/F/A||Appears like gelatine POP.|
|Platinum||1873 (1879-1914)||Platinum||-||Paper||L/M/F/A||Paper fibres visible. Degraded transfer image on facing paper. Little image fading.|
|Gum bichromate||1856 (1890's-1920's)||Pigment||Gum arabic||Paper||L/M/F/A||May be glossier in darker areas. May be slight relief in image. Pigment particles visible under low magnification. Pigment colour.|
|Carbon print||1855/64 (1868-1940's)||Pigment||Gelatin||Paper||L/M/F/A||May be glossier in darker areas. More pronounced relief image. Little image fading. Pigment colour.|
|Gelatin dry plate negative||1871/73 (-1930's)||Silver (chemically developed)||Gelatin||Glass||L||Usually non-image strip near border. Smooth, even, thin coating.|
|Silver gelatin fibre/ paper based prints||1882 (-1960's) (POP) |
1873 (-1960's) (DOP)
|Silver (POP & DOP)||Gelatin||Paper||L/M/F/A||Sometimes very pronounced mirror tarnish for DOP.|
|Cellulose nitrate||1889 (-1950)||Silver (chemically developed)||Gelatin||Cellulose nitrate||L/Plastic or paper wallets||Sometimes edge printed "CELLULOSE NITRATE"|
|Cellulose acetate||Late 1920's (to present)||Silver (chemically developed)||Gelatin||Cellulose acetate||L/Plastic or paper wallets||Sometimes edge printed "SAFETY"|
|Polyester||1940's/50's (to present)||Silver (chemically developed)||Gelatin||Polyester||L/Plastic or paper wallets||Not usually edge printed.|
|Resin-coated paper||1972 (to present)||Silver (chemically developed)||Gelatin||Polyethylene coated paper||L/M/F/A||Tends to lie flat. More plastic than plain paper supports.|
POP = printed out print. This means that the sensitised printing paper is exposed, in contact with a negative, to light (usually daylight) until the final image appears. The printing paper is then fixed and washed. There is no development stage. They are usually sepia in colour.
Physically developed images use silver ions from the developer which are deposited on the silver of the latent image. The silver does not usually come from the photographic emulsion itself, unless it has been dissolved in the developer solution first.
DOP = developed out prints. In this case the sensitised printing paper is exposed, (usually under an enlarger) to artificial light for a shorter period of time than POP. This produces a latent image which is not visible to the human eye. The printing paper is then placed in a developer until the image appears. The silver in the image comes from the sensitised paper itself. After this, the printing paper is placed in a stop bath, fixed and washed. It is much quicker to produce than POP and the process is more controlled and the results more predictable.
Table "Aid to identification of the most common black and white historical photographic processes and supports" from page 4 of The British Library, Preservation Advisory Centre - Photographic material.