The ziatype is a modern noble metal printing process developed by Richard Sullivan in the 1990s — a refined and simplified approach to palladium printing that produces images of extraordinary warmth, richness, and archival permanence. Named after Zia, New Mexico, where Sullivan lived and worked, the ziatype uses lithium palladium chloride as the metal salt (rather than the traditional palladium chloride and sodium chloropalladite used in classic palladium printing), combined with ferric ammonium oxalate as the light-sensitive agent. The result is a process that is more controllable, more consistent, and capable of producing a wider range of tonal colours — from cool grey to warm brown to rich chocolate — than traditional palladium printing. This guide covers the chemistry, sensitiser preparation, paper coating, exposure, development, tonal control, and the singular beauty of ziatype prints.
How the Ziatype Differs from Traditional Palladium Printing
Traditional platinum/palladium printing uses a two-part sensitiser: an iron salt (ferric oxalate) and a noble metal salt (potassium chloroplatinite for platinum, sodium chloropalladite or palladium chloride for palladium). The ziatype replaces the palladium salt with lithium palladium chloride (Li₂PdCl₄), which is more soluble, more stable in solution, and produces more consistent results. The lithium ion also influences the tonal colour of the final print — contributing to the ziatype's characteristic warm, rich tonality. Additionally, the ziatype workflow allows for easy contrast control through the addition of small amounts of gold, platinum, or other metal salts to the sensitiser — giving the printer precise control over image contrast without changing development chemistry.
Sensitiser Preparation
The ziatype sensitiser consists of two main components: Solution 1 — ferric ammonium oxalate (the light-sensitive iron salt), approximately 25% concentration in distilled water; Solution 2 — lithium palladium chloride, approximately 20% concentration in distilled water. To prepare the working sensitiser, mix equal parts of Solution 1 and Solution 2. For contrast control, add small amounts of a contrast agent: gold chloride solution (increases contrast), or sodium platinum chloride (increases contrast while shifting colour towards cooler tones). The ratio of ferric ammonium oxalate to palladium salt, and the addition of contrast agents, allows fine-tuning of both the tonal range and the colour of the final print. Kits from Bostick & Sullivan provide pre-made solutions and detailed mixing instructions.
Paper, Coating, Exposure, and Development
Use high-quality, unsized or lightly sized fine art paper: Bergger COT 320, Arches Platine, Hahnemühle Platinum Rag, or Revere Platinum. The paper must be free of optical brighteners. Coat the paper under dim tungsten light or safelight using a brush, glass rod, or coating blade. Dry completely in the dark. Expose through a calibrated digital negative under UV light — exposure times vary from 3–15 minutes depending on UV intensity. The ziatype is a developing-out process (unlike the printing-out Van Dyke): the exposed print shows little or no visible image until developed. Develop in a tray of potassium oxalate developer (approximately 25% concentration at room temperature) for 2–3 minutes — the image appears rapidly and reaches full density. Clear the print in successive baths of dilute citric acid or EDTA to remove unexposed iron salts. Wash thoroughly and dry flat.
Tonal Colour and Contrast Control
The ziatype's great strength is its tonal versatility. By adjusting the sensitiser formula, the printer controls both the image colour and the contrast range. Pure palladium ziatypes produce a warm, rich brown. Adding gold chloride shifts the colour towards neutral or cool tones while also increasing contrast. Adding platinum shifts towards cool grey with enhanced contrast. The developer temperature also affects colour — warmer developer produces slightly warmer tones. Humidity during coating and drying influences contrast and colour as well — higher humidity tends to increase contrast. These variables give the ziatype printer an extraordinary range of creative control within a single process.
The Ziatype Aesthetic
Ziatype prints combine the permanence and tonal beauty of noble metal printing with a warmth and richness that distinguish them from cooler platinum prints. The image sits within the paper fibres — not on the surface — giving the print a soft, matte, luminous quality. Shadows are deep and velvety; highlights are delicate and nuanced. The overall impression is of a handmade object of quiet luxury — the warm brown tones evoking antique photographs while the extraordinary tonal range and sharp detail are unmistakably modern. The ziatype is the ideal process for photographers who love the palladium aesthetic but want more control, consistency, and tonal versatility than traditional palladium printing offers.
The ziatype is palladium printing refined — warm, rich, controllable, and permanent.
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