A Step Wedge is the foundation on which an expressive, modern Platinum Print is created. As a chemical process, the relationship between negative and final print is non-linear. That is to say, the density and contrast of highlights, mid-tones and shadows on the negative do not translate directly to similar values on the resulting print. Successful Platinum/Palladium prints are made from a negative that is both high in contrast and very dense. These are undesirable qualities for a negative that is to be scanned or printed optically, but for a Platinum/Palladium Print, result in an image of ‘correct’ density and contrast.
By making a test print with a ‘Step Wedge’; a transparent substrate of known densities, the printmaker can create a correction curve that matches the negative to the properties of the emulsion it will be printed on.
This Step Wedge has been created to match negatives to a Palladium rich emulsion (5:2pd/pt), coated on Arches Platine, and developed in 3 month old Potassium Oxalate Developer. Changes in humidity, temperature, paper from batch to batch and dozens of subtle variables all contribute to a cumulative change in the appearance of a print…. so I make Step Wedges frequently, and take notes ALL of the time. This is one of my favourite ‘recipes’ for Platinum Portraits of children and families, because the Palladium and developer combine to create great warmth, while the Platinum helps with the richness and depth.
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