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 generations due to the difficulty of obtaining consistent results.
Dr. Mike Ware revived and refined the process, publishing reliable modern gold printing formulae that produce images rivalling platinum prints in permanence and tonal beauty. His current version is the New Chrysotype.
Chemistry
Ware New Chrysotype Sensitiser
The New Chrysotype uses three stock solutions. The gold is held as a stable complex with a sulphur-containing ligand, which stops the iron salt reducing it in the bottle:
| Stock solution | Make-up |
|---|---|
| A — Ligand (1.4 M) | 12.5 g 3,3'-thiodipropanoic acid in about 30 ml water, neutralised with 7.4 g anhydrous sodium carbonate, made up to 50 ml |
| B — Gold (0.35 M) | 5.0 g sodium tetrachloroaurate(III) dihydrate made up to 36 ml |
| C — Iron (1.4 M) | 30 g ammonium ferric oxalate in 33 ml water (makes about 50 ml) |
Working Solution
For the standard mix, combine A, B and C in the volume ratio 4:4:1 (for 10 ml: 4.44 ml A, 4.44 ml B, 1.12 ml C). Add B to A drop by drop, letting each drop decolourise, then add C. Ware says the standard mix lasts at least two hours (at least 30 minutes for any ratio between 2:4:1 and 6:4:1); it cannot be stored and plates gold onto its container as it decomposes.
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.
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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: Let the coating settle until the sheen disappears, then dry in a warm (about 40 °C) air stream for about 10 minutes. Store coated paper dry and in the dark, and expose the same day if possible.
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Humidity and exposure: Before exposure, condition the paper at a controlled humidity; this sets the colour (about 10% RH gives pinks and reddish-browns, 45% purple, 80% bluish-black). Contact print under UV light, typically for 1–10 minutes (a modest UV source may need only one or two). At high humidity the image largely prints out; at low humidity it forms mainly in development.
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Development: Develop for up to 10 minutes in water, about 1% disodium EDTA, or 1–2% citric acid. Do not use tetrasodium EDTA as a developer (it causes iron stains).
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Clearing: Rinse, then clear in 5% tetrasodium EDTA for 10 minutes; rinse; 2.5% sodium sulphite (or hypo clearing agent) for 10 minutes; rinse; and 5% tetrasodium EDTA again for 10 minutes.
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Washing: Wash for 30–60 minutes in running water.
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Drying: Air dry or blot and dry flat.
Print Characteristics
Chrysotype produces images with:
- Colour: Pink, red-brown, purple, blue-black or grey-black, controlled mainly by humidity and paper (gelatin-sized papers favour reds and pinks)
- 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 | High |
| Permanence | Excellent | Excellent |
| Colour | Pink to blue-black, set by humidity | Neutral grey to warm brown |
| Colour control | Humidity | Pt:Pd ratio, humidity, developer |
Troubleshooting
| Problem | Likely Cause | Solution |
|---|---|---|
| Weak image | Underexposure; exhausted sensitiser | Increase exposure; use fresh solution |
| Staining | Insufficient clearing | Extend or refresh the EDTA and sulphite clearing baths |
| Uneven tones | Uneven coating; humidity issues | Improve technique; control environment |
| Low Dmax | Wrong paper; humidity too low | Try different paper; condition the paper at higher humidity |
Safety
| Chemical | Hazard | Precautions |
|---|---|---|
| Ammonium ferric oxalate | Harmful if swallowed or in contact with skin (H302, H312) | Gloves; avoid ingestion |
| Gold salts (sodium tetrachloroaurate) | Corrosive; toxic | Gloves and eye protection essential; use plastic, not steel, spatulas |
| EDTA salts and sodium sulphite | Disodium EDTA harmful if inhaled; clearing salts irritant | Avoid dust; gloves |
| Sodium carbonate | Eye irritant (H319); neutralisation foams strongly | Use a tall vessel; eye protection |
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.
Mike Ware, The New Chrysotype Process (mikeware.co.uk) Ware's full working instructions, free on his website.
Sources
- The New Chrysotype Process, Mike Ware
- Publications list, Mike Ware