gum bichromate over platinum print. (9 x 6 in.)
Duotone (two) negatives are used for this print, cool tones are printed in platinum and warmer tones printed in gum.
In Photoshop and in RGB mode the channels of the image are split. The Red channel is used for the cool platinum negative and the Green and Blue channels combined and used for the warm toned Gum negative. I picked this technique up from Sam Wang and it is quite effective in generating cool and warm negatives from an image for these gum over prints.
Adjustment curves specific to the platinum or gum printing process are then applied, registration marks added and the negatives printed out onto Pictorico transparency using an Epson 3880 in ABW mode.
To avoid registration problems I dry mount my printing paper, usually Bergger’s COT320 paper to thin aluminum plates. This way I don’t need to worry about the shrinkage of the paper causing registration problems during the process. After making the platinum print in the usual way the print is allowed to dry before applying two coats of size to avoid problems with pigment staining the paper during the gum process.
Colour and iridescence are then added in several successive layers using the gum negative. This Marching trees print image is made up of 9 gum layers, each layer slowly building up the colour and iridescence. The use of the warm negative helps focus the gum to where I want it, the sky and misty areas in this case. The last layer uses an Ivory black pigment to snap the contrast back in.
After drying for the final time, the print is removed from the aluminium plate and mounted onto acid free water colour paper for framing.
These prints are a labour of love over 2-3 weeks to reach the end point. Not all make it through due to silly mistakes and clumsy handling, usually a result of me printing too late into the night. When a print like the one shown above in this post does make it through, it is quite an ah ah moment when you see it is finally finished. The depth in the colour and shadows, and the subtle iridescence makes Marching Trees quite an exquisite print.
Detail of surface showing how the mica added to the pigment adds a timely Christmas sparkle.