Non-Silver Photographic Processes
Cyanotype
CYANOTYPE, 1842-1920
Iron-based paper positive with Prussian blue as the image material
Paper is brushed with a mixed solution of potassium ferricyanide and ferric ammonium citrate and dried. The paper is placed in direct tight contact with a negative and exposed to light. The image is "printed-out" during exposure with shades of blue in proportion to the amount of light received through different densities of the negative. The image is then washed in water to remove unexposed chemicals and dried. No fixing is necessary for this process.
The blue color will fade if exposed to light for extended periods.
Liberty Hyde Bailey. Cyanotype, late 1880s.
2 1/2 x 4 1/2 in.
In 1888, botanist and horticulturalist Liberty Hyde Bailey assumed the chair of Practical and Experimental Horticulture at Cornell University. The simple and inexpensive cyanotype process became popular with amateurs and scientists between about 1880 and 1910.
Carbon Print
CARBON PRINT, 1865-1950
Non-silver paper based positive with pigment as final image material in gelatin layer
Paper is coated with a mixture of carbon ink (or other suitable pigment) and bichromated gelatin and is exposed to light through direct contact with a negative. The gelatin hardens selectively in proportion to the amount of light it receives through the different densities of the negative. The exposed carbon/gelatin paper is then pressed against a second sheet of paper and soaked in hot water. The unhardened gelatin/carbon mixture dissolves in hot water and the original paper is peeled away, leaving the hardened gelatin and carbon image registered on the second sheet of paper.
The dark areas of the print have more gelatin than the light areas and will appear glossier. The pigment used is usually very stable and the image generally shows no signs of fading.
Unidentified. Carbon Print, ca. 1875.
3 5/8 x 5 1/4 in.
Fisk University’s Jubilee Singers achieved worldwide fame. Their tours throughout England, Europe and America raised funds for their pioneering African-American university and countered stereotypes about black musicianship.
Platinum Print
PLATINUM PRINT (platinotype), 1880-1930
Iron-based paper positive with platinum as the final image material
Paper is brushed with a mixed solution of iron and platinum compounds and exposed to light through direct contact with a negative, resulting in a faint image. The image is then developed in a solution of potassium oxalate, causing the image to become fully pronounced. A subsequent hydrochloric acid solution was often used to clear the iron compound left in the paper, which was then washed in water. If the iron compound and/or the hydrochloric acid are not removed completely, the paper will discolor and become brittle over time.
A platinum print has a cool black/grey image tone. The platinum image is extremely stable and shows no signs of fading even after the paper support becomes yellow and brittle.
Burt Green Wilder Collection. Platinum Print, late 1880s.
7 1/8 x 5 3/8 in.
Photography gave science a new way to record specimens. Burt Green Wilder (1841-1925) was a comparative anatomist and professor at Cornell University from 1867 to 1910. This platinum print shows a cross-section of a human brain, one of over 600 specimens in Wilder’s collection, to which his own brain was added after his death.