The oilprint process (Schildt)

Anders Schildt gives us his take on the oilprint process.

Always be careful when handling chemicals. Read the health and safety instructions.


First I must say that I owe all my initial knowledge about this fascinating process to the author of the book The keepers of light. I have since gone further experimenting, and find that this process gives me the ultimate ability to make unique prints. I am not restricted by the size of the negative, because I have found – under influence of the Starntwins work – ways of doing oil prints in the size I want. I am now working with a print which will be 3 x 6 feet!

Ingredients

  • A large negative – since it is a contact process. Make them rather contrasty in the darkroom, (Agfa has still big greyscale-sheets) or on computer: Scan your photograph and resize it, – make it greyscale and print out. You can print very big negatives in sheets, which easily can be put together by tape. To get a transparent negative I also put my paper negative(s) through a Zerox, also to get nice contrast and density!
  • A thick copper print paper. I always use the Dutch paper “Zerkall”. It is a good idea to resize the paper by putting it into water for a while and then dry it before using it.
  • Potassium dichromate for sensitising the paper. 3 grams in 100ml water. NOTE: It is very toxic, so be very, very careful!
  • Edible gelatine
  • Brushes and sponges
  • A contact frame or glass plate
  • Sun light or a UV light source
  • Ink or thick oil colour pigment

Explanation of the process

Gelatine normally dissolves when adding water, but when mixing Potassium Dichromate and gelatine and exposing it to UV light, the gelatine hardens, and does not dissolve as readily. A paper soaked with a gelatine and Potassium Dichromate solution is exposed to sunlight. The solution is hardened in proportion to the light passing through the negative, and the unexposed chemicals, that did not harden, are washed off. The more light, the harder solution. You then have a “water print” which you can see faintly against the light. Then carefully, but firmly you put on stiff lithographic ink on the very wet gelatine, and then take off the surplus ink with brushes and sponges. The white areas of the negative, where the light has hardened the gelatine, will resist the ink, and the dark areas of the print, where the gelatine is still soft, will absorb the ink, and an oil-printed photograph is made.

The process

1Coat the paper with gelatine
Make a thick solution of edible gelatine and pour it on the paper with quick movements to avoid bubbles or stripes. No gelatine, no oil print. I use a sponge to help me. Let it dry and then do it again – and again. 3 times should be sufficient. Dry the print.

2Add Potassium dichromate
When the print is dry, pour the Potassium dichromate over the gelatine in an even (yellow coloured) way – use a sponge and rubber gloves. This can be done in tungsten light, but away from sunlight. Let the print dry in a dark place.

3Expose your print to UV light
When the print is dry again, put your negative on the paper (use tape on one side) and place it under a glass plate or contact print frame to make the print sharp. Expose it to sun or UV light until the highlight details in the image just come visible. My prints need approximately 3-5 min. If over exposed, the gelatine will be hardened and unable to absorb water and no print will occur.

4Wash and dry the print
Wash the print immediately afterwards in running water at about 21g C (70gF) until the ‘yellow stain’ is gone. When the paper is washed clean, dry the surface gently with toiler paper in a calm action to remove the surface water.

That was the easy part!

5Inking the print
Press gently, but firmly adding the stiff ink with a brush or sponge. A small layer of ink should cover the whole print. Then take a special oil print-brush or a sponge, and with a dabbing fast movement, you remove the ink. The ink can be any colour, to create multicolour prints. If the print dries when working, you can submerge it again in water, but not over 21 degrees C. It will then absorb water again, and you can keep on working. You can keep working over a few days, as long as the ink is still wet!

Alternative way of adding colours

Another way to colour your print is to scan a picture into your computer. You can then add or remove colour as you please. Make a digital copy of the image, turn it to a greyscale, slightly contrasty negative by inverting the picture. Print out the first negative, and then print out your colour print on copper printing paper. I find that pale colours works best.

NOTE: I know for a fact that HP – deskjet 1120c accepts heavyweight paper, and Epson does not!! Don’t you ruin your printer if you are not sure.

Experiment

Prepare the printed-out copper printing paper with gelatine and make an oil print over this printout. Great results, yet somewhat unpredictable. Keep on experimenting – I feel I am alone using this method, and would like to hear from other with results or experiences!


3 Comments

  1. Amit Arun
    Posted November 5, 2010 at 5:57 pm | Permalink

    hello,

    I’m not a photographer but I think this method would be useful in electronics to make PCBs (I just need two colours, fully exposed and unexposed regions). I had mediocre experience with toner transfer and was looking for a way to make inexpensive photoresist.

    I initially tried with gum bichromate but unfortunately the UV hardened film didn’t give any protection to copper against the ferric chloride etchant.

    The photogravure method seems more viable, I’m going to experiment with it soon. I’ll let you know how it goes.

  2. yashasvi
    Posted October 22, 2013 at 8:38 pm | Permalink

    can you give out more details about inking I m not able to understand that part

  3. Posted January 30, 2014 at 11:29 am | Permalink

    Hi!
    finally I found another person who does this technique!!
    I’m from Italy and I did a workshop about it here in Italy!
    my teacher usually use the photographic paper, he told me it works better.
    I’d like to use the cotton paper more precious, but with it I have no good results… the ink cover all the image… I read your method and probably the probem is on the quantity of gelatine and time exposure! now I must try your method!!
    keep in touch!

    thanks!

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