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Collotype

Once it was practiced by many fine lithographic print houses in Europe and America. Until recent years it was the most delicate process and the only process of producing high quality photo-realistic prints on regular paper. Today just few professionals know of its existence.
Try searching for collotype on the Internet.

YAHOO has only ONE collotype listing and this listing has nothig to do with real collotype.

   
This 1:10 enlargment shows typical collotype grain

The basics of collotype.

Safety note: All dichromates are poisonous. When working with them in liquid form use rubber gloves and glasses. In handling dry crystals use gauze mask. In the case of skin contact use 3% solution of hydrogen peroxide, which decomposes these substances.

1.Prepare 10-12 mm thick glass plate grinded with sand paper.

2.Formula for undercoat:
Gelatin1.5 grams
Distilled Water50 ml.
Potassium Alum1 gram
Sodium Silicate5 ml.

First, prepare the gelatin solution using 30-35 ml. of water by soaking gelatin at least for 39 min in it and then warming to 130 degrees F. Use the rest of water for making Potassium Alum solution. Then add it to the gelatin stirring well. Only after that mix it with Sodium Silicate. Keep this order otherwise undercoat will not adhere to the plate and may peel off during printing.

3. Put a thin layer of the undercoat solution on the printing plate and let it dry.

*Step 4 must be done under dimmed orange light.

4.Prepare photo sensitive emulsion by soaking and then warming 10 grams of gelatin in 75 ml of water. Dissolve 1 gram of potassium dichromate or ammonium dichromate in 10 ml of water.

Mix both solutions, filter through a medium size mesh and pour on to the printing plate which should be warmed up and leveled inside the "oven" . Spread the emulsion evenly and set the oven on 110 degrees F.

5. Dry plate is light sensitive and should be exposed and developed during 1-2 days.

6. After exposure plate is washed under cold running water until yellow color disappears (usually for 2 hours) and then dried under the room temperature.

7. Just before printing the plate needs to be "presoaked" in the mixture of 3 parts of glycerin and 2 parts of water for approximately 30 minutes. It may be gently applied with the soft roller as many times as needed.

8. Carefully blot the excess of glycerin solution from the plate with soft paper towel.

The plate is ready for inking with lithographic inks. Use soft rollers.

The detailed description of the process can be found in the book STUDIO COLLOTYPE by Kent B. Kirby ( the owner of Light-print Press) published in 1988.

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