I was asked once if it’s possible to print Gum over Van Dyke. I posted an answer saying I thought it was possible but someone tweeted this response to my answer: “Gum over Van Dyke actually shouldn’t work because the dichromate is a silver bleaching agent.” I knew this was not true but I had no proof –thus, I embarked on a test that resulted in the following print.
Although printing Cyanotype over Van Dyke is not possible because the Potassium Ferricyanide in the Cyanotype formula is an oxidizing agent that removes silver and therefore would etch out the silver nitrate in the existing Van Dyke print underneath. However, the Potassium Dichromate in the Gum formula does not bleach silver and can be used to print over Van Dyke prints. In fact, it was typical for traditional Gum Printers to print gum over Platinum to add color (see Steichen print below).
For my print, I used a gray Rives BFK which I preshrunk, sized and hardened. I printed the Van Dyke image using the Photographers’ Formulary Van Dyke Brown Printing Kit—although, it would be cheaper to purchase the bulk chemicals if you’re going to me making a lot of prints. Afterwards, I coated the print with gum sensitizer at a 1:1 ratio and used Winsor Newton Lamp Black pigment with a short exposure (aprox. 1 min 30 sec) to add color and density to the shadows. Then, using a positive rather than a negative, I coated the print with gum sensitizer at a 1:1 ratio and used Winsor Newton Permanent White gauche with a long exposure (aprox. 6 – 6 ½ min) to add color and tone to the highlights.
Although I’m pleased with the results of the experiment, the print itself can be improved. The print was made using a RGB negative and positive but the curve I applied was the curve I used when I was using Gray Scale negatives. The RGB negative with the Gray Scale curve is too contrasty and looses detail in the highlights. I’ve since revised the curve (a modified gray scale curve) for RGB negatives which will be the topic of my next blog post.
Edward Steichen (1879– 1973): “The Pond – Moonlight” (1904)
