Historical Context
Ziatype was developed at Bostick & Sullivan by Richard Sullivan in 1997, with Carl Weese, as a printing-out palladium process. It is a variation of Giuseppe Pizzighelli's 19th-century printing-out process and was named after the Zia sun symbol of the New Mexico pueblo peoples, which appears on the New Mexico state flag.
The process uses lithium palladium chloride (or caesium palladium chloride for warmer tones) with ammonium ferric oxalate. In the Pizzighelli and Malde-Ware printing-out methods, colour and contrast are controlled largely by humidity; in the Ziatype they are controlled chemically as well, which makes results easier to repeat. Prints match platinum/palladium in archival quality.
Chemistry
Sensitiser Solutions
Most printers buy the solutions ready-made as the Bostick & Sullivan Ziatype kit:
| Solution | Role |
|---|---|
| Ammonium ferric oxalate | Light-sensitive iron salt |
| Lithium palladium chloride | Image metal (cool, neutral black) |
| Caesium palladium chloride (optional) | Replaces lithium palladium for warm brown tones |
| Gold chloride, 5% | Replaces part of the palladium: raises contrast, gives cool and split tones |
| Ammonium dichromate, 1% | 1–2 drops raise contrast strongly and cool the tone (carcinogen: see Safety) |
| Sodium tungstate, 40% | Warms the tone and lowers contrast |
Working Solution
Start with equal drops of ammonium ferric oxalate and lithium palladium: Bostick & Sullivan give 10–15 drops in total for a 4×5" print, 15–20 for 5×7", 30–35 for 6×9" and 40–45 for 8×10". Their base mix for a neutral 5×7" print is 12 drops of each (20 of each for 8×10"), which prints cool neutral black while the coating is wet; a drier coating prints warmer. They also suggest one drop of Tween 20 in the mix (not with Arches Platine). For more contrast, replace some of the palladium drops with gold chloride (not with caesium palladium: the two cannot be combined), or add a drop of 1% ammonium dichromate.
Procedure
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Paper selection: High-quality 100% cotton papers sized for platinum printing. Bostick & Sullivan recommend Arches Platine, Hahnemühle Platinum Rag, Revere Platinum, Bergger COT 320 and Japanese kozo papers.
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Humidity: Humidity is essential. Bostick & Sullivan recommend working with the room at 50–65% relative humidity and at 65 °F (18 °C) or above. Moist paper gives cool, neutral tones and full print-out; drier paper gives warmer tones.
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Coating: Under subdued light with no UV, mix the drops and apply with a brush or glass rod. Work quickly and evenly.
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Drying: Let the coating soak in for two or three minutes, then dry with a cool air stream (about a minute) until the surface is just dry. The paper should sound slightly "dead" when snapped and must not be wet enough to transfer emulsion to the negative. Do not use hot air unless you want warmer tones. Expose promptly.
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Exposure: Contact print under UV light. Ziatype is a printing-out process—you will see the image appear during exposure. It is typically 2–3 stops faster than developed-out platinum/palladium. Expose until the highlights show detail.
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Development and clearing: Immerse the print in running water for at least 2 minutes; this completes the image. Then clear in an EDTA and sodium bisulfite bath (1–2 tablespoons of each per 1.5 litres of water) for 10–15 minutes, until no yellow remains in the highlights; distilled water is best for the bath.
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Washing: Bostick & Sullivan give a final wash of about 10 minutes. Many printers wash longer; Ware's printing-out method specifies at least 30 minutes.
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Drying: Air dry or blot and dry flat.
Print Characteristics
- Colour: From cold neutral black to warm brown, set by humidity and additives; gold gives cool, blue or purple split tones
- Tonal range: Excellent, similar to platinum/palladium
- Dmax: High, with rich shadows
- Permanence: Archival—palladium is extremely stable
- Surface: Matte, image embedded in paper fibres
Contrast Control
Ziatype offers excellent contrast control through:
- Gold chloride: Replacing part of the palladium with 5% gold chloride increases contrast and cools the tone
- Ammonium dichromate: One or two drops of a 1% solution increase contrast strongly (and increase exposure time)
- Sodium tungstate: Lowers contrast and warms the tone
- Humidity: Changes in paper moisture affect both colour and contrast, so keep it consistent
Comparison with Kallitype
| Aspect | Ziatype | Kallitype |
|---|---|---|
| Final metal | Palladium | Silver |
| Permanence | Excellent | Good (with toning) |
| Cost | Higher (palladium) | Lower |
| Toning needed | No | Recommended |
| Colour | Warm to neutral | Brown (variable with developer) |
Troubleshooting
| Problem | Likely Cause | Solution |
|---|---|---|
| Weak image | Underexposure; exhausted sensitiser | Increase exposure; fresh solution |
| Staining | Insufficient clearing | Extend clearing time; fresh EDTA/bisulfite bath |
| Low contrast | Not enough contrast agent; paper too dry | Replace some palladium with gold chloride, or add a drop of 1% ammonium dichromate; check humidity |
| Uneven tones | Coating or humidity issues | Improve technique |
| Grainy appearance | Paper unsuitable | Try different paper |
Safety
| Chemical | Hazard | Precautions |
|---|---|---|
| Ammonium ferric oxalate | Harmful if swallowed or in contact with skin (H302, H312) | Gloves; no eating/drinking |
| Lithium palladium chloride | Palladium salts are skin sensitisers and can damage eyes | Gloves and eye protection; avoid dust |
| Ammonium dichromate (1%) | Danger: may cause cancer, genetic defects and harm to fertility (Carc./Muta./Repr. 1B); fatal if inhaled as dust; corrosive; skin and respiratory sensitiser; REACH Annex XIV | Use only the ready-made dilute solution; nitrile gloves; dispose of as hazardous waste |
| Gold chloride | Corrosive; harmful if swallowed | Gloves and eye protection |
| EDTA and sodium bisulfite | Disodium EDTA harmful if inhaled; sodium bisulfite harmful if swallowed and releases sulphur dioxide with acids | Avoid dust; ventilate |
Further Reading
Bostick & Sullivan, Ziatype Printing Kit Instructions (bostick-sullivan.com) The original source for Ziatype materials and instructions, from the company where Richard Sullivan developed the process.
Dick Arentz, Platinum & Palladium Printing (Focal Press, 2000) While focused on traditional platinum/palladium, contains relevant technical information applicable to ziatype.
Christina Z. Anderson, Gum Printing and Other Amazing Contact Printing Processes Includes coverage of ziatype in the context of iron-based alternative processes.
Sources
- Ziatype Printing Kit Instructions, Bostick & Sullivan
- The Platino-Palladiotype Process, Mike Ware
- Ammonium dichromate substance information, ECHA