Rubber pressure

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Hugo Henneberg , Am Kanal , rubber print, around 1900

The rubber printing , also Gummibichromatverfahren , is a so-called Alternative Process .

history

The use of the rubber printing process reached its peak, especially in art photography at the turn of the 20th century. Both the French Louis-Alphonse Poitevin for the year 1855 and the English John Pouncy (1818-1894) are considered to be the inventors of the process . Pouncy had the process patented in 1858.

The rubber prints made around 1900 by the French photographers Robert Demachy and Constant Puyo as well as those by the Hofmeister brothers and the Wiener Kleeblatts group ( Heinrich Kühn , Hans Watzek and Hugo Henneberg ) from German-speaking countries are considered to be of particular artistic value .

A basic distinction must be made between simple and multilayered or combined rubber printing. While the former consists of only one print layer and only reproduces a few tonal gradations, multiple layers of rubber can be copied on top of each other thanks to the multiple rubber printing, which enables a wider range of tonal values. The three-color process according to Hans Watzek is a further development of multi-layer rubber printing .

Technology of rubber printing

Although potassium or ammonium dichromate are insensitive to light in their pure state, they are sensitized to photochemical reactions in connection with colloids. Colloids are glue-like substances such as gum arabic , isinglass or gelatine . Radiation from light causes the chromates to react instantaneously with the colloids, which are then tanned or hardened depending on the exposure to light and thus lose their solubility in water. The rubber printing process uses this property. An emulsion of chromate salts, gum arabic and color pigments is prepared, which is applied as a thin layer on paper. The paper coated in this way is exposed through a negative, color separation negative, in the contact process, whereupon the exposed areas tan and become water-insoluble. The rubber layer is then washed out. The areas hardened by the light remain. The color pigments are bound in the exposed areas so that an image emerges.

method

With rubber printing, the negative is placed on the photosensitive paper and exposed in the contact process, so a negative should be selected first, which can then be enlarged as desired. Thanks to the contact process, the finished image corresponds to the size of the negative. Before exposure occurs, the following steps must be observed:

The choice of paper

The paper serves as the carrier material for the light-sensitive rubber emulsion and should therefore not be too smooth, otherwise the layer could slip off. Since it is exposed to water baths, strong watercolor or handmade paper is particularly suitable for this. Before the paper can be used, it should be shrunk so that the registration does not change with multiple prints. To shrink the paper, it is placed in a 50 to 60 degree Celsius hot water bath and after about 15 to 30 minutes removed and dried. The colored rubber emulsion must not penetrate the paper fibers, which is why well sized paper should be used. If multiple printing is planned, the gluing is usually not sufficient so that re-gluing is necessary. For this purpose, 25 g of gelatine is dissolved in 500 ml of water and evenly applied to the paper with a bristle brush and then dried. The choice of paper decisively determines the grain and the character of the picture. In order to achieve special artistic effects, watercolor or expensive hand-made paper was deliberately used.

The color

The color is later mixed with the chrome rubber emulsion and should be water-soluble and not oily. Theodor Hofmeister, an important German art photographer, refers, among other things, to tempera and watercolors and continues: “Every artist strives to ensure that his pictures remain unchanged in terms of the color effect and that after centuries still show the same face as when the picture was completed. We still admire that today in the pictures of the old masters. ”Among the photographic processes, rubber printing in particular can meet these demands. After exposure, the color pigments are firmly bound in the hardened layer, do not peel off and - depending on the lightfastness of the color - retain their luminosity for a very long time. Also, the addition of color can be seen as a fundamental change in photography. In the 1850s and around the turn of the century, photographs were still black and white, but simple rubber printing produced monochrome images, with brown tones being preferred. The multiple pressure makes it possible to combine different colors. In order to create a special mood, color stylizations were mostly sought - absolutely naturalistic reproduction is not possible with this method.

The chrome rubber emulsion

The light-sensitive coating consists of an aqueous solution of gum arabic , potassium or ammonium dichromate and an additive of color. It is applied with a brush in subdued lamplight. The action of light then causes the chromates to react momentarily with the colloids, which, depending on the light, are tanned or harden and thus lose their solubility in water. A 30% solution can be produced with ammonium dichromate. This is more light-sensitive than the 10% potassium dichromate solution, the latter being used more often. For the gum solution, gum arabic is dissolved in water - this can take several hours - usually a 40% solution is used. Rubber printing is not a silver halide process. In practice, the chromate solution can be mixed with the dissolved gum and paint in different ways. Ultimately, it is important that the light-sensitive layer is applied as evenly as possible and not too thick. "Up until 1897, paper was prepared for rubber printing by mixing a 40 percent rubber solution with a pigment and a 10 percent solution of potassium dichromate and applying it thinly to the paper." The newer method is that of James Packham describes the method developed, “according to which the paper is first soaked in the chromate and then coated with the rubber paint. Due to its water-repellent power, the chromate acts like a doubled sizing of the paper, so that the rubber ink does not penetrate the paper fiber as much. ”Finally, it should be pointed out that the chromate content determines the hardness of the image, so that softer images are created by a high chromate content and harder images result from a lower chromate content. If the gum arabic solution is mixed with the potassium dichromate solution in a ratio of 1: 1, it is called force pressure. The mid-tone print is achieved by the ratio 1: 2, the highlight print finally by the ratio 1: 3. The light print "should cover everything with a glaze and only leave the paper completely free at the highest lights." Since only one tone value can be copied per printing process, different prints are usually combined to achieve the desired result.

The exposure

When the paper has been coated with the emulsion and dried, it is photosensitive and can be exposed directly under a negative in the contact process. The main focus of the process is on the correct exposure time, whereby various factors play a role: such as sensitivity and thickness of the spread, density of the negative, use of the color, exposure to artificial light and sunlight in winter or summer. The exposure time is on the order of about ten minutes and is basically the shorter the thinner the layer and the less paint and rubber are used. A thick spread and a short exposure can produce a coarse grain; conversely, a fine-grained image can be created through a thin layer and a long exposure. The choice of color is also crucial. “Experience has shown that green and blue tones need shorter - around a third - copying time, such as black and yellow or even brown, which have to copy the longest.” The exact exposure time must be met so that the image is not overexposed or underexposed. A photometer is often used as an aid. In order to achieve a special blurring, the paper can also be exposed from the back, as Theodor Hofmeister shows.

The development

After the original has been exposed under a negative, the exposed areas have hardened and become insoluble in water. In order to obtain a finished image, the unexposed and therefore water-soluble layer must be washed out. "You put the exposed sheet, layer down, in cold [...] water, after about 10 minutes" the discolored water is poured off. The aim of the bath is to separate the color of the unexposed areas and the light-sensitive chromates contained in the layer from the substrate. After that, new water is refilled and the arc is left to “develop undisturbed by checking for a while. The image is ready after 40 minutes. ”During development in the water bath, the resulting image can be influenced in various ways. To get a coarse grain, sawdust can be added to the water. In addition, a so-called forced development can be used with a water jet. The beam deliberately removes more color so that the lights can be emphasized, for example. The rubber print is ready after the picture has dried. With the combined rubber pressure, a new print is carried out.

It should be noted that rubber printing is basically a simple process, but requires a lot of skill for a good result.

The advantages of the procedure

Compared to other photographic processes, rubber printing and the associated processing can be carried out in subdued or even full daylight, since the chemical reaction of the bichromates to the colloids takes place very slowly when they are wet. In addition, the chromates are completely washed out, so that the finished image has an unlimited shelf life and does not darken. Another reason for the durability is that the color and thus the image is "attached directly to the paper surface by an insoluble substance." This is different with pigment printing , where the image is transferred to another surface and is therefore possible that the paint will peel off over time. The ability to re-prepare and re-copy a finished impression in order to achieve an improved result are major advantages of rubber printing. The grain size can be changed and colors can be combined. For example, copying clouds into a landscape in two work steps is a popular approach in combination printing. Basically every work step - from the choice of paper to the exposure - offers an opportunity to intervene in the resulting image. Ultimately, this is the decisive advantage of rubber printing, which is why its use was and is particularly in the artistic field.

The importance of rubber printing for the art photography movement around 1900

For the Pictorialists , photography represented a form of artistic creation, whereby independent photographic means were used. The technical perfection of these means was, for example, a life goal for Heinrich Kühn, an important Pictorialist. In order to achieve "the greatest imaginable freedom of image design", they improved the camera, recording material and copying processes. The most important method of copying this movement was rubber printing, as this technique in particular enables intervention in the creation of the image. This freedom is reflected, for example, in the use of color, which makes the photographer “independent of the brown and blue tones of the silver, iron and platinum processes”. Photography, which in the art discourse was often viewed as a purely technical / mechanical medium, got a different status with rubber printing. A mechanical camera provided the negative, but the finished image was always unique. When it comes to rubber printing, the decisive factor for the resulting image is the artist and his or her actions - for example, that the character of the finished image is already influenced by the choice of paper. In addition, relatively large rubber prints were made, which were compared to paintings by their format alone. It was precisely this comparison that the art photographers sought. The editor of the weekly photographic newspaper wrote in 1906 that “it [...] is strange how one can use this method to reproduce the character of various art techniques, for example that of pastels, watercolors or oil paintings, and how each practitioner has his own particular one Expresses character in it. The pictures by Henneberg have z. B. the character of a watercolor, that of Watzek that of an oil painting. "

The history of rubber printing

In 1852 Henry Fox Talbot found that the exposed emulsion of potassium dichromate and gelatin lost its water solubility and swellability. Louis-Alphonse Poitevin developed pigment and rubber printing from this in 1855. However, the images were reversed and halftones could not be displayed. Abbé Laborde and JC Burnett fixed this problem a little later. John Pouncy finally patented the process in England in 1858 and exhibited its results publicly. After that, the process was partially used for copying landscape, portrait and architectural images, but rubber printing was soon forgotten. It was not used again until the 1890s. "The English photographer and co-founder of the Linked Ring, Alfred Maskell, had taken up the process again in 1893 and suggested Robert Demachy of the Photo-Club de Paris to experiment with rubber printing." Other sources put the French A. Rouillé Ladevèze in the foreground, who in 1894 Had exhibited rubber prints in the Salon de Paris, which prompted Demachy to present his first results in the Photo-Club de Paris a year later. A contemporary witness, Johannes Gaedicke, editor of the weekly photographic newspaper, seems to connect the information: “In 1893 the English art photographer Alfred Maskell exhibited rubber prints in London. The first to publish a process for producing pigment images without transferring using gum as a binder was Rouillé-Ladevèze, who described the process in his brochure: Sepia-Photo et Sanguine-Photo (Paris 1894, Gauthier-Villars et fils) stated how it is mostly still used today. ”In any case, the success story of rubber printing began with the pictorialist photographer. The rediscovery of rubber printing and its widespread use around the turn of the century can be associated with a special interest in the decorative effect of the visual arts, as represented by Art Nouveau and the various secession movements at that time. At the same time, with their rubber prints, the amateurs could more easily stand out from the professional photographers who avoided the time-consuming process. After Paris, “in the London and Brussels salons of 1895 [...] some rubber prints by Demachy [...] attracted attention because of their artistic treatment. At the end of 1895, five rubber prints by Demachy were on view in the exhibition of the Vienna Camera Club.

Hans Watzek , still life , three-color rubber print, around 1898

In the German-speaking countries, rubber printing spread from Vienna. “While Theodor and Oscar Hofmeister only showed charcoal and pigment prints in 1896, in 1897 they only exhibited rubber prints. They were fascinated by this fine printing process, which Heinrich Kühn first presented in Hamburg in 1896. ”(The picture exhibited by Kühn is entitled“ Twilight ”.)

Hans Watzek developed the three-color rubber print in the winter of 1896 in order to be able to present it on New Year's Day 1897. In the same year Kühn's first experiments in color were shown in Hamburg, where they were again immediately taken up by the brothers Theodor and Oskar Hofmeister, followed in 1898 by the Berlin photographers with multicolored pictures. Together with the British photographer Alfred Maskell , Robert Demachy wrote a description of the process, which was published in English in 1897 and in French in 1898 under the title Le Procédé à la gomme bichromatée ou photo aquatinte. Then, for example, the American photographer Alfred Stieglitz became aware of the rubber printing process. With the art photography movement, photography found its place in the museum space, so in 1902 only rubber prints were shown at the annual exhibition of the Vienna Secession. The possibilities of intervening in the process and thus actively creating a picture as an artist represent the advantages of rubber printing. According to Theodor Hofmeister, there is no coincidence in rubber printing because everything is in the hands of the artist. Of course, this opinion was controversial and the rubber print was also heavily criticized because of its blurring. With the new vision of the 1920s at the latest , rubber printing was of little importance. In the USA the process was still most common until the 1940 / 50s. In recent years, rubber printing has experienced a renaissance as a countermovement to digital photography. However, the heyday of rubber printing was around the turn of the century.

Hazard warning

Ammonium dichromate and potassium dichromate are carcinogenic , mutagenic and toxic to reproduction .

literature

  • Wolfgang Autenrieth: New and old techniques of etching and fine printing processes - An alchemistic workshop book for erasers: From 'witch's meal and dragon's blood' to the photopolymer layer. Tips, tricks, instructions and recipes from five centuries , Krauchenwies 2010, 230 pages, ISBN 978-3-00-035619-3 , ( table of contents , (→ excerpts online) )
  • JM Eder: The pigment process, oil, bromine oil and gum printing and related photographer. Copying process, Halle: Knapp, 1926 (reprinted by Lindemans Buchhandlung, Stuttgart, 1990, ISBN 3928126091 )
  • Hofmeister, Theodor: Rubber printing and its usability as an artistic means of expression in photography, Volume 2, Halle a. S .: Wilhelm Knapp, 1907.

Web links

Individual evidence

  1. ↑ See Hofmeister, Theodor: The rubber printing and its usability as an artistic means of expression in photography, Volume 2, Halle a. S .: Wilhelm Knapp, 1907, p. 1.
  2. ↑ See Rosenberg, Gert: Bildentstehungstechniken der Fotografie, in: Geschichte der Fotografie in Österreich, Volume 2, Bad Ischl: Ed. By the Association for the Development of the History of Photography in Austria, exhibition catalog, 1983, p. 27.
  3. ↑ http://www.riat-serra.org/graph-7.pdf p. 38 - October 24, 2010
  4. ^ Pizzighelli, G .: Instructions for Photography, Halle a. S .: Wilhelm Knapp, 1904, p. 283.
  5. ↑ Hofmeister, Theodor: The rubber printing and its usability as an artistic means of expression in photography, Volume 2, Halle a. S .: Wilhelm Knapp, 1907, p. 7.
  6. ↑ See Loescher, Fritz: Hamburger Brief, in: Photographische Mitteilungen 43/1906, p. 256.
  7. ↑ See Hofmeister, Theodor: Reply to the Hamburger Brief, in: Photographische Mitteilungen 43/1906, p. 356.
  8. ↑ http://www.riat-serra.org/graph-7.pdf p. 38 - October 24, 2010
  9. ↑ Gaedicke, Joh .: Der Gummidruck, A Guide for Amateurs and Professional Photographers, Berlin: Gustav Schmidt, 1906, p. 20.
  10. ↑ Ibid. P. 33.
  11. ↑ Gaedicke, Joh .: Der Gummidruck, A Guide for Amateurs and Professional Photographers, Berlin: Gustav Schmidt, 1906, p. 34.
  12. ↑ Cf. Pizzighelli, G .: Instructions for Photography, Halle a. S .: Wilhelm Knapp, 1904, p. 286.
  13. ↑ Heidtmann, Frank: Fine art printing processes today, 1st edition, Berlin, Berlin, 1978. P. 56.
  14. ↑ See Hofmeister, Theodor: The rubber printing and its usability as an artistic means of expression in photography, Volume 2, Halle a. S .: Wilhelm Knapp, 1907, p. 14.
  15. ↑ Ibid. P. 15.
  16. ↑ Ibid. P. 20f.
  17. ↑ Ibid. P. 16.
  18. ↑ See Gaedicke, Joh .: Der Gummidruck, A Guide for Amateurs and Professional Photographers, Berlin: Gustav Schmidt, 1906, p. 12.
  19. ↑ Ibid. P. 13.
  20. ↑ See ibid.
  21. ↑ Cf. Pizzighelli, G .: Instructions for Photography, Halle a. S .: Wilhelm Knapp, 1904, p. 293.
  22. ↑ Cf. Gaedicke, Joh .: Der Gummidruck, A Guide for Amateurs and Professional Photographers, Berlin: Gustav Schmidt, 1906, p. 123.
  23. ↑ Faber, Monika; Mahler, Astrid (Ed.): Heinrich Kühn. The perfect photography, Ostfildern 2010, p. 11.
  24. ↑ Ibid. P. 17
  25. ^ Behrens, Friedrich: The rubber print as an artistic means of expression, in: Photographische Mitteilungen 34/1897.
  26. ↑ Gaedicke, Joh .: Der Gummidruck, A Guide for Amateurs and Professional Photographers, Berlin: Gustav Schmidt, 1906, p. 63.
  27. ↑ http://www.riat-serra.org/graph-7.pdf p. 39 - October 24, 2010
  28. ↑ Rosenberg, Gert: Bildentstehungstechniken der Fotografie, in: History of Photography in Austria, Volume 2, Bad Ischl: Ed. By the Association for the Development of the History of Photography in Austria, exhibition catalog, 1983, p. 27.
  29. ↑ http://www.photoinfos.com/Fotoliteratur/Fotorestaurator/Fotorestaurator1994-03.pdf p. April 9, 2011.
  30. ^ Koenig, Thilo: Fine platinum pictures, international art photography and America's contribution to the Hamburg exhibitions. In: Art photography around 1900, The Ernst Juhl Collection , Hamburg: Museum for Art and Industry Hamburg, 1989, p. 48f.
  31. ↑ Gaedicke, Joh .: Der Gummidruck, A Guide for Amateurs and Professional Photographers, Berlin: Gustav Schmidt, 1906, p. 4.
  32. ↑ Ibid. P. 4f.
  33. ↑ Kruse, Margret: Theodor and Oscar Hofmeister, From the sketch of ideas to rubber printing, In: Art photography around 1900, The Ernst Juhl Collection, Hamburg: Museum for Art and Commerce Hamburg, 1989, p. 43.
  34. ^ Koenig, Thilo: Fine platinum pictures, international art photography and America's contribution to the Hamburg exhibitions. In: Art photography around 1900, The Ernst Juhl Collection, Hamburg: Museum for Art and Industry Hamburg, 1989, p. 49.
  35. ↑ DNB 977070689/34 , p. 19-28 October 2010.
  36. ↑ Photographisches Central-Blatt 8/1902 s. 28.
  37. ↑ See reply to the Hamburg letter: Theodor Hofmeister, p. 355.