This is the classic Cyanotype or Blueprint a contact printing process that yields a Cyan to indigo print. You may also want to try a faster formula.
| solution A | ferric ammonium citrate | 20.0g | |||
| water 125 f | 100ml | ||||
| solution B | potassium ferricyanide | 8g | |||
| water 125 f | 100ml |
Mix and store each solution separately. To mix the sensitizer combine equal amounts of each solution in the order given just prior to use. Any leftover sensitizer should be discarded after each session Coat your paper with a thin even coating. Thoroughly dry the sensitized paper before exposure. Remember that the sensitizer contains chemicals that will damage your negatives if the y come in contact with the wet emulsion. To be safe you can insert a piece of clear acetate between the negative and the emulsion during the exposure.
Exposure
Cyanotypes require a lot of exposure thus it is best to do so outdoors in bright midday sun (1 hour). If you must use an artificial light source one with high amounts of UV is required. Even so the exposure time will be unmanageablely long. Expose the print until the broad highlight areas are a green/bronze tone.
Development
After development rinse the print in running water until all of the yellow effluent has totally rinsed off. Allow the print to air dry.
Special notes
If you add too much potassium ferricyanide solution the exposure will dramatically increase.