Catatype

from Wikipedia, the free encyclopedia

The catatype is a photographic fine printing process for the reproduction of photographic prints developed in 1901 by the chemist and Nobel Prize winner Wilhelm Ostwald and his assistant Oscar Gros . The process gets its name from the underlying chemical reaction type, a catalysis . Ostwald and Gros also called their process "reproduction of photographic recordings without light" or "photography without light".

Manufacturing

Wilhelm Ostwald and Oscar Gros, the inventors of the catatype

To make a copy, hydrogen peroxide dissolved in diethyl ether is applied to an ordinary photographic negative. The ether evaporates and a thin layer of hydrogen peroxide remains on the plate. The first chemical reaction now begins. In the layer of the negative metallic silver is distributed in very fine grains. In the dark areas they are closer to one another, in the lighter areas they are more thinly scattered and in the light glass areas they are almost completely absent. Finely divided silver has the property that it breaks down hydrogen peroxide into water and oxygen. The silver itself remains unchanged. The finely divided silver is the catalyst in this case ; where there is more of it in the negative, more hydrogen peroxide is decomposed; where it is absent, the hydrogen peroxide remains unchanged. After a while, the negative is pressed onto ordinary gelatine paper for a few seconds to a minute .

The hydrogen peroxide immediately penetrates the gelatin layer, as shown in the drawing on the negative. In the layer there is an invisible positive image made of hydrogen peroxide. The picture is then immersed in a solution of manganese salts; At the places where the hydrogen peroxide adheres, a precipitate of brownstone forms , which is denser wherever there is more hydrogen peroxide, but is thinner where only a small amount of it has stuck. The result is a finely tinted brown image that is in the wrong relationship to the negative in light and shadow, i.e. a perfect positive. Instead of the manganese salts, other chemical substances can also be selected, on which hydrogen peroxide also has an oxidizing effect, so that other tints are created.

literature

  • Advances and inventions of the modern age - photography without light. In: The Gazebo. Anthology 1903, p. 373.
  • Josef Maria Eder : Detailed handbook of photography. Volume 4, Part 2: The pigment process, bromine and rubber printing, blueprint and dusting processes with chromates, pinatypia, kodachrome, hydrotypes, copying processes with coloring organic compounds, diazotype processes, images with tanning and chromogenic developers and artificial resins. 4th completely revised and enlarged edition. Knapp, Halle (Saale) 1926, p. 422, (reprint. Lindemanns, Stuttgart 1990, ISBN 3-928126-09-1 ).