Cyanotype

Historical Context

Invented by Sir John Herschel in 1842, cyanotype was the first successful non-silver photographic printing process. Anna Atkins used it to create the first photographically illustrated book, British Algae: Cyanotype Impressions (1843-53). The process later became commercially important as the "blueprint" for reproducing architectural and engineering drawings.

Chemistry

The traditional cyanotype uses two solutions that are mixed immediately before coating:

Solution A — Ferric Ammonium Citrate (green form)

Solution B — Potassium Ferricyanide

Working Solution: Mix equal parts Solution A and Solution B immediately before use.

Shelf Life: Individual solutions last 6-12 months stored in dark bottles. Solution A is susceptible to mould growth—discard if cloudy or contaminated. Mixed working solution should be used within 24 hours.

Procedure

1. Paper preparation: Select appropriate paper. No pre-treatment typically required for traditional cyanotype.

2. Coating: Under subdued tungsten light (not fluorescent or daylight), mix equal volumes of Solutions A and B. Apply to paper with brush or rod. Coat evenly, avoiding puddles.

3. Drying: Dry coated paper in darkness. Can be force-dried with gentle heat (hairdryer on low) but air drying produces more consistent results. Paper turns from yellow-green to grey-green when dry.

4. Exposure: Place negative in contact with sensitised paper, emulsion to emulsion. Expose to UV light. Exposure times vary enormously depending on light source:

   • Bright sun: 5-20 minutes
   • UV fluorescent tubes: 15-45 minutes
   • Overcast sky: 30-90 minutes

5. Judging exposure: The image should appear as a grey-blue negative with olive-green shadows. Highlights will be yellow-green. With experience, you'll learn to judge by the reversal of shadow tones.

6. Processing: Wash in running water for 5-15 minutes. The yellow highlight areas clear to white; shadows deepen to rich blue. Over-washing can reduce Dmax.

7. Oxidation: Full blue colour develops during drying. Can be accelerated by a brief dip in dilute hydrogen peroxide (0.3% solution) but this isn't necessary.

8. Drying: Air dry or blot and dry flat.

Contrast Control

The traditional cyanotype has inherently high contrast. Methods to modify:

• Ammonium dichromate: Adding 2-5% to the sensitiser increases contrast further (rarely needed)
• Citric acid: Adding citric acid to the sensitiser reduces contrast
• Exposure manipulation: Overexposure followed by reduction in weak sodium carbonate can compress highlights
• Paper selection: Softer papers produce lower contrast

Toning

Traditional cyanotype can be toned to alter colour:

Tannic acid toning (produces blue-black to purple-black tones)

1. Bleach in weak sodium carbonate until blue converts to yellow
2. Rinse thoroughly
3. Immerse in 5% tannic acid solution until desired colour achieved
4. Rinse and dry

Tea/Coffee toning (produces warm brown-blacks)

Same bleaching process, then immerse in strong tea or coffee solution.

Note: Toning involves bleaching the image first; if you don't like the result, you cannot recover the original.

Troubleshooting

New Cyanotype (Mike Ware)

Developed by Dr. Mike Ware in 1994, the New Cyanotype addresses several shortcomings of the traditional process. It uses ferric ammonium oxalate instead of the citrate, producing faster printing, better tonal separation, and improved adhesion to paper.

Key Advantages

• Single solution (no mixing at time of use)
• Much faster exposure (2-4 minutes vs 20-40+ minutes)
• Better tonal range and Dmax
• Improved paper adhesion
• No tackiness problems with negatives

New Cyanotype Sensitiser

Note: The New Cyanotype contains oxalates, which are toxic if ingested. Exercise greater care in handling compared to the traditional formula.

Paper Selection

Recommended Papers

• Arches Platine: Industry standard, works excellently
• Hahnemühle Platinum Rag: Specifically formulated for iron processes
• Bergger COT320: Heavy cotton rag, excellent results
• Stonehenge: Affordable option that works well
• Fabriano Artistico: Good general-purpose watercolour paper

Avoid papers with alkaline buffers (most "archival" papers marked acid-free), as these can inhibit the iron chemistry.

Safety

Traditional cyanotype is one of the safest alternative processes and is suitable for educational settings with appropriate supervision.

Further Reading

Mike Ware, Cyanotype: The History, Science and Art of Photographic Printing in Prussian Blue (Science Museum/NMSI, 1999) The first published monograph on cyanotype. Now out of print but available as a free 400-page PDF download ("Cyanomicon") on mikeware.co.uk. Covers history, chemistry, conservation, and practice.

Christina Z. Anderson, Cyanotype: The Blueprint in Contemporary Practice (Routledge, 2019) Part of the Contemporary Practices series. Over 100 papers tested, 400 photographs from nearly 80 artists. Covers classic, new, and other cyanotype formulas plus toning and alternative surfaces.

Christina Z. Anderson, Cyanotype Toning (Routledge) Part of the Routledge Contemporary Practices series, dedicated entirely to toning methods for cyanotype.

Christopher James, The Book of Alternative Photographic Processes, 3rd Edition (Cengage Learning, 2015) The definitive comprehensive text on alternative processes, with extensive coverage of cyanotype alongside 27 other chapters.

Mike Ware's website (mikeware.co.uk) Primary source for the New Cyanotype formula, with free downloads of complete workshop notes and technical papers.