Sun printing

Anna Atkins algae cyanotype

Sun printing may refer to various printing techniques which use sunlight as a developing or fixative agent.

Techniques

Cyanotype

Main article: Cyanotype

Cyanotype, also referred to as "blueprinting", is the oldest non-silver photographic printing process.^[1] It involves exposing materials which have been treated with a solution of potassium ferricyanide and ferric ammonium citrate to a UV light source such as the sun. Negative or positive images can be obtained by blocking UV light from reaching the sensitized material. For example, a negative image can be produced by placing a leaf upon paper treated with this solution and exposing to sunlight for 10 to 20 minutes. The paper will retain the image of the leaf after it has been rinsed with water. Once the paper dries, parts that were exposed to the sun will turn a shade of Prussian blue (ferric ferrocyanide), while parts that were covered by the leaf will remain white.

Light-sensitive vat dyes

A specialized type of vat dye called Inkodye is also used for sun-printing due to its light-sensitive quality.^[2] Unlike other vat dyes which use oxygen to develop their color, Inkodyes are developed by light.^[3] These dyes are suspended in leuco form appearing colorless until they are exposed to UV. Their usage resembles that of cyanotype, but unlike cyanotype Inkodyes are primarily used on textiles and exist in a full range of colors.^[1] Exposure times vary from 3 to 15 minutes depending on the desired color and intensity of light.^[4] Once exposed, the sensitized material is washed in soapy water to remove dye from unexposed areas. Such dyes are typically used by craftspeople, fabric printers and artists and can be printed with photographic negatives, resist paste or through a silk screen.

Potassium dichromate

Sun printing may also refer to a photographic process using potassium dichromate which produces a negative plate for conventional lithographic printing. The process uses a film of gelatine spread on a flat and rigid surface. This is coated with a dilute solution of potassium dichromate and dried in low light conditions. A translucent positive is secured in tight contact with the treated gelatine layer and exposed to bright sunlight for a period of up to 30 minutes. During this time the sunlight and potassium dichromate tan the gelatine exposed to light. The plate is developed by washing in warm water and removing the untanned gelatine. Once dry, a relief print is revealed on the plate. The surface can be inked and printed in a hand press to produce any number of identical prints of the original subject.

References

1 2 House, Suda (1981). Artistic Photographic Processes. Amphoto Books. pp. 84–88. ISBN 0-8174-3541-7.
↑ How to Dye and Paint Fabric with Light
↑ Epp, Diane (1995). The Chemistry of Vat Dyes. Terrific Science Press. pp. 5–8. ISBN 1-883822-05-X.
↑ Ray Laury, Jean (2010). Imagery on Fabric: A Complete Surface Design Handbook. C&T Publishing. pp. 122–123. ISBN 1-57120-034-7.

External links

Inkodye - Light-sensitive vat dyes

Photography

Outline

Terminology	35 mm equivalent focal length Angle of view Aperture Black and white Chromatic aberration Circle of confusion Color balance Color temperature Depth of field Depth of focus Exposure Exposure compensation Exposure value F-number Film format Film speed Focal length Guide number Hyperfocal distance Metering mode Perspective distortion Photograph Photographic printing Photographic processes Reciprocity Red-eye effect Science of photography Shutter speed Sync Zone System

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Techniques	Afocal Bokeh Brenizer Contre-jour Cyanotype ETTR Fill flash Fireworks Harris shutter HDRI High-speed Holography Infrared Kirlian Kite aerial Long-exposure Macro Mordançage Multiple exposure Night Panning Panoramic Photogram Print toning Redscale Rephotography Rollout Scanography Sabatier effect Stereoscopy Stopping down Strip Slit-scan Sun printing Tilt–shift Miniature faking Time-lapse Ultraviolet Vignetting Xerography

Composition	Diagonal method Framing Headroom Lead room Rule of thirds Simplicity

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Color photography	Color Print film Reversal film Color management color space primary color CMYK color model RGB color model

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