Cyanotype |
A positive image can be produced by exposing it to a source of ultraviolet light (such as sunlight) with a negative. The UV light reduces the iron(III) to iron(II). This is followed by a complex reaction of the iron(II) complex with ferricyanide. The result is an insoluble, blue dye (ferric ferrocyanide) known as Prussian blue.
Upon exposure to ultraviolet light (such as that in sunlight), the iron in the unexposed areas will reduce, turning the paper a steel-grey-blue color. The extent of color change is dependent on the amount of UV light, but acceptable results are usually obtained after 10-20 minute exposures on a dark, gloomy day. The highlight values should appear overexposed as the water wash will reduce the final print values. Prints can be made with large format negatives and lithography film, or everyday objects can be used to make photograms.
After exposure, developing of the picture involves the yellow unreacted iron solution being rinsed off with running water. Although the blue color darkens upon drying, the effect can be accelerated by soaking the print in a 6% (v/v) solution of 3% (household) hydrogen peroxide. The water-soluble iron(III) salts are washed away, while the non-water-soluble Prussian blue remains in the paper. This is what gives the picture its typical blue color.
VanDyke
Van Dyke Brown is an early photographic printing process. The process was so named due to the similarity of the print color to that of a brown oil paint named for Flemish painter Van Dyck.
VanDyke Print |
The negative is placed on the thoroughly dried coated substrate, and is then weighted with a piece of glass. Frequent printers often use a printing frame to ease the checking of printing progress without disturbing the registration, or alignment, of the negative on the paper. These printing frames also ease the printing of a second coat over the same image.
Lumin Print by Angel Pei |
Lumen Printing is also an alternative to printing contact prints or photograms, again requiring minimum time, equipment and money. This is a black and white photographic process, although with that in mind, you will be surprised by the results (and colour) of your creations. That is the beauty of photography.
Alternative Processes Site
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