Platinum/Palladium Process
International · Platinum / Palladium Print 1873–present
The most expensive black-and-white printing process, and the one photographers reach for when they want the longest tonal scale available. The image is metallic platinum embedded in the paper fibre itself, not held in a coating on top of it.
Origin
Patented by William Willis in 1873 and commercially available as ready-coated paper from the 1880s, platinum became the prestige print of the Pictorialist movement — Stieglitz, Steichen, Käsebier and Coburn all used it extensively. The First World War ended that: platinum was requisitioned for military and industrial use, prices rose sharply, and commercial paper was discontinued in 1916. Palladium was substituted as a cheaper alternative, and most modern practice uses a mix of the two.
Technique
Paper is hand-coated with ferric oxalate and a platinum or palladium salt, dried, and exposed to ultraviolet under a negative in contact — there is no enlargement, so the negative must be the size of the finished print. Light reduces the iron, which then reduces the platinum salt to metallic platinum. Development in potassium oxalate is nearly instantaneous, and the remaining iron is cleared in acid baths. Because the metal sits in the paper fibre rather than in a gelatin layer, the surface is completely matte with no gloss whatsoever.
The palette
Neutral to warm grey-black, with an exceptionally long and smooth tonal scale — platinum can hold separation in the highlights and deep shadows simultaneously in a way silver cannot, and the mid-tones are unusually extended. Palladium runs warmer and browner than platinum; the ratio between them is a deliberate control. Adding mercury or gold, or altering the humidity during coating, shifts the colour further.
Legacy
Its permanence is essentially indefinite, since platinum is among the most chemically inert of metals — a properly cleared platinum print should outlast its paper. The combination of extreme cost, hand-coating and contact printing has made it the connoisseur's process, and it is the standard against which fine black-and-white printing is still measured.
Palette
The colours reconstructed for this artist, with the reasoning behind each.