The Van Dyke Brown Process
Various Van Dyke formulas exist. The one used here was concocted by Roger Hein, incited by Richard Kuzniak. It combines ferric ammonium citrate — a light-sensitive agent — with tartaric acid and silver nitrate, which forms the final image.
A puddle of this solution is brushed or rolled onto acid-free paper — here, Arches Platine — and hung to dry in the dark. When the paper is ready, the printer lays a 4X5" negative on the coated area and forces the two surfaces together under a sheet of glass in a contact printing frame.
The contents of the printing frame are exposed to bright UV light for ten minutes or so, until a rusty brown image develops on the emulsion under the negative. When the image seems detailed enough, the frame is opened and the negative is separated from the paper.
The paper is agitated in a tray of water to complete the development stage. Next, the image is 'fixed' in a bath of sodium thiosulfate, which deepens the colour and ensures permanence. The print is rinsed in water again to halt the fixing action, and soaked briefly in sodium sulfite to remove any traces of sodium thiosulfate left in the fibres of the paper. Finally, it is washed in running water and air dried overnight.
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