Historical Context
Chrysotype (from Greek chrysos, gold) was invented by Sir John Herschel in 1842, just three years after the announcement of photography itself. Herschel created it alongside cyanotype, and both processes use iron salts as sensitisers. However, while cyanotype thrived, chrysotype remained largely forgotten for over 150 years due to the difficulty of obtaining consistent results.
Dr. Mike Ware revived and refined the process in the late 1990s, developing reliable modern formulations that produce images rivalling platinum prints in permanence and tonal beauty.
Chemistry
Ware Chrysotype Sensitiser
The Ware method uses a two-solution approach:
Solution A — Iron Sensitiser
| Component | Amount |
|---|---|
| Ammonium ferric oxalate | 30 g |
| Distilled water | 100 ml |
Solution B — Gold Salt
| Component | Amount |
|---|---|
| Gold(III) chloride (HAuCl4) | 5 g |
| Distilled water | 100 ml |
Working Solution
Mix equal parts Solution A and Solution B immediately before coating. The combined solution has limited shelf life.
Procedure
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Paper selection: Use well-sized, 100% cotton papers. Arches Platine, Hahnemuhle Platinum Rag, or similar papers designed for platinum/palladium printing work well.
-
Coating: Under subdued tungsten light, apply sensitiser with a glass rod or hake brush. Work quickly as the solution is light-sensitive once mixed.
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Drying: Dry in darkness using gentle heat (hair dryer on low) or air dry in a dark box.
-
Exposure: Contact print under UV light. Chrysotype is a develop-out process—you will see little or no image during exposure. Test strips are essential.
-
Development: Develop in a dilute solution of sodium thiosulfate:
- 1% sodium thiosulfate for 2-3 minutes
- The gold image appears during development
-
Clearing: Clear in citric acid (3%) for 5 minutes to remove residual iron.
-
Washing: Wash for 30 minutes in running water.
-
Drying: Air dry or blot and dry flat.
Print Characteristics
Chrysotype produces images with:
- Colour: Deep purple-black to red-brown depending on paper and processing
- Permanence: Exceptional—gold is among the most stable of all photographic metals
- Tonal range: Long, subtle tonal scale similar to platinum
- Surface: Matte, embedded in paper fibres
Comparison with Platinum/Palladium
| Aspect | Chrysotype | Platinum/Palladium |
|---|---|---|
| Final metal | Gold | Platinum or palladium |
| Cost | High | Very high |
| Permanence | Excellent | Excellent |
| Colour | Purple-black | Neutral grey to warm brown |
| Availability | Gold more accessible | Platinum increasingly rare |
Troubleshooting
| Problem | Likely Cause | Solution |
|---|---|---|
| Weak image | Underexposure; exhausted sensitiser | Increase exposure; use fresh solution |
| Staining | Insufficient clearing | Extend citric acid bath |
| Uneven tones | Uneven coating; humidity issues | Improve technique; control environment |
| Low Dmax | Wrong paper; insufficient gold | Try different paper; increase gold concentration |
Safety
| Chemical | Hazard | Precautions |
|---|---|---|
| Ammonium ferric oxalate | Toxic if ingested; skin irritant | Gloves; avoid ingestion |
| Gold(III) chloride | Corrosive; toxic | Gloves essential; careful handling |
| Sodium thiosulfate | Low toxicity | Standard precautions |
| Citric acid | Mild irritant | Standard precautions |
Further Reading
Mike Ware, Gold in Photography: The History and Art of Chrysotype (Ffotoffilm Publishing, 2006) The definitive reference by the process's modern developer. Covers history, chemistry, and detailed practical instructions.
Mike Ware's website (mikeware.co.uk) Free downloads of technical papers and ongoing research into iron-based and precious metal processes.
Christina Z. Anderson, Gum Printing and Other Amazing Contact Printing Processes Coverage of chrysotype alongside other iron-based processes with practical guidance.