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COLLOTYPE (also Phototypie, Albertotype) 

Collotype developed in parallel with photography and was a first method of reproducing photographs and printing them true to the original. This printing technique was the first printing process that could be used industrially.
Collotype is a flat printing process. It involves printing by hand from exposed gelatine directly onto handmade paper. This technique is also regarded as the "king of reproduction processes" because it can produce true halftones and does not require an artificial grid. 

In printing, halftone refers to a mixture of a solid tone and the colour white, or a grey value created by mixing black and white. Many printing processes are not capable of producing true halftones. Therefore, halftones are screened. This is the case with offset printing, for example. These printing processes produce screened images that only simulate halftones. 

As the name suggests, collotype uses daylight or artificial light. This takes advantage of the property of gelatine to change its surface under the influence of light by treating it with certain salts and thus absorbing ink. In the production of printing plates, light acts in a similar way to "nature's crayon" by "inscribing" the motif to be printed into the gelatine layer. 

The complex production process requires a high degree of experience and a feeling for the sensitive technology of the craftsman in order to "shape" the "living substance" of gelatine as a print template and thus to give the printed work a form that is as true to the original as possible.

The printing form is a glass plate with an emulsion layer of gelatine and light-sensitive salts. Exposure to these salts triggers a chemically differentiated tanning process, whereby the areas of the gelatine layer that are exposed more strongly and thus hardened more intensively accept the ink more strongly and release it onto the paper to be printed with the corresponding intensity.

A fine gelatine relief, the so-called collotype-wrinkles, is already formed during the production of the printing plate as a characteristic of collotype. As the ink-bearing printing element, it is responsible for the screenless tonal value decomposition and produces the high resolution typical of collotype printing, which is unrivalled even by modern electrode grids. 

Due to the loss-free print quality, collotype is considered the noblest and most accomplished reproduction technique. However, this also means that the time and monetary expenditure is significantly higher compared to today's digital and offset printing.

In digital and offset printing - in contrast to collotype - the ink is applied through colour dots or grids (very fine screens). However, this is always associated with a loss of quality.

Collotype was widespread around 1900 and was mainly used for illustrating books or for printing postcards. Initially, there were no known processes that reproduced drawings, paintings or photographs in comparable quality. 

After the process gradually became less widespread in the middle of the 20th century, it was still used outside the immediate artistic field for the facsimile reproduction of works of art such as paintings, medieval manuscripts and documents. For this, the reproduction quality was unrivalled.


A glass plate about 8 to 10 mm thick serves as the printing plate carrier. After the plate has been preheated and levelled, two layers of different thickness are poured onto it one after the other. While the priming, thinner adhesive layer does not yet contain any sensitizer, the thicker copy layer consists of gelatine and the sensitizer, a chromium salt. The plate is then dried again and cooled. During this process, the wrinkled grain structure is formed due to the tensions in the gelatine skin.  
Using a strong light source, the exposure process takes place in the copying frame in direct contact with a page-perfect half-tone negative, which was previously produced as a printout of an inkjet printer on film. In order to be able to transfer the fine nuances of highlights and shadows to the gelatine layer, the negative requires careful and also expert digital retouching using image processing programmes.
For colour printing, in turn, a printing plate is produced for each necessary colour and consequently a corresponding negative is also required for each colour. Due to the exposure, a tanning (hardening) of the gelatine layer takes place at the exposed areas. Depending on the degree of partial hardening, the gelatine loses its swelling capacity and its solubility in water. A latent positive image is thus created on the gelatine plate by the effect of light.
The exposed plate is then soaked in cold water to wash out the unexposed chromium salts and to allow the gelatine layer to swell in these areas. The plate must then be allowed to dry thoroughly. The dried plate is moistened again, this time with a glycerine-water mixture to prevent it from releasing the moisture prematurely.
The gelatine now swells again according to the intensity of the tanning and thus acquires its differentiated ink absorption capacity. Whereas the unexposed and untanned areas absorb the moisture, thus swelling and later repelling the ink, the exposed and hardened areas, depending on the degree of tanning, repel water and thus accept the viscous ink.  
The printing process takes place on a hand press.
Handmade paper is used as the printing substrate. The so-called collotype inks are very rich in light- and water-fast pigments, contain linseed oil and varnish and are therefore viscous. Ink application can be influenced by the sequence of inks, the frequency of inking or the hardness of the rollers. Likewise, corrections to the ink acceptance on the printing plate are possible through partial dampening or various chemical treatments.
However, the final ink mix is only produced on the printed sheet.
The colour tones, ink application and paper tone determine the impression of the work.  The printing results are particularly dependent on the reaction of the organic component gelatine as well as a number of factors such as temperature and humidity, but essentially on the experience of the printers, which precludes standardisation of this process.  
Finding the right recipe for the composition of the layer, the ideal temperature and humidity, the necessary exposure time, the right roller, the ideal way of rolling in, the ideal consistency of the ink; these are the parameters that determine the success or failure of a collotype. However, it is precisely this creative possibility of influencing them that proves to be particularly interesting for the artistic field.

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