Julian Pearce Photography Julian Pearce Photography

Technical notes

Technical note on platinum/palladium printing

The photographs for the Girraween portfolio were all taken on 11x14 inch Ilford HP5 film using a Chamonix Ultra Large Format camera with a range of new and second hand lenses from 210mm to 600mm in focal length (equivalent to 21 to 60mm focal length on a 35 mm camera). The lenses most used were a 305mm Schneider G Claron and a 450mm Nikkor M.

The film was all developed by hand in trays using Pyrocat HD developer. This is a staining developer which has the advantage that it provides higher density in respect of UV than visible light. The same negative can therefore be used for both silver gelatin printing as well as processes such as platinum/palladium printing which require negatives of high effective contrast. (In this case, the negatives for the Girraween portfolio were intended to be printed solely as platinum/palladium prints.)

The platinum/palladium photographic paper is prepared by hand coating onto watercolour paper with a mixture of sensitiser (ferric oxalate) and salts of palladium and platinum (palladium chloride and potassium chloroplatinite). Usually some small amount of contrast agent is used by adding a drop or two of potassium chlorate or, in the case of a mixture containing palladium only, sodium chloroplatinate. After drying, the coated paper is exposed through the negative to UV light from a bank of UV tubes for between 10 and 30 minutes depending on the density of the negative.

The exposed paper shows a faint image but to be fully revealed needs to be developed. In the Girraween portfolio, potassium oxalate developer at a temperature of 40c was used as this provides a warm tone well suited to the subject matter. The process of development is one of the extraordinary sights in traditional photographs as the image is revealed instantaneously when the developer is poured over the exposed paper. After development, the photograph is washed briefly in water then cleared firstly in a weak bath (2%) of phosphoric acid and then in an alkaline bath comprising sodium sulphite and EDTA. These clearing baths remove residual ferric salts. After clearing, the print is washed again to archival standard.

February 2013