Cyanotype

Cyanotype is an analog photographic process in which UV light reacts with an emulsion that is sensitive to UV light and turns blue. The remaining, unexposed or only partially exposed emulsion is rinsed off with water, thus stopping the exposure.

The studio is equipped with four UV light devices. Formats up to A1 can be exposed. Transparent films for the digital printing of negatives are possible up to A3 format. Larger acrylic and glass plates are available. Suitable paper and special photographic paper are also available.

Explanation

Cyanotypes can be used to expose photo negatives as well as objects, materials or stencils to UV light and capture them on paper and other materials such as wood and fabric. In a relatively short time, an interesting blue-colored »imprint« of the exposed original is obtained.

The liquid is made from two iron salts that are only light-sensitive when mixed together. They are therefore stored separately and only the amount that you want to use soon is mixed.

Technical procedure

First, two iron salts in powder form are dissolved separately in water. 10 g potassium ferricyanide (red prussiate of potash) and 25 g ammonium iron citrate are each mixed with 100 ml water. The two mixtures can be stored in the refrigerator in two separate amber glass bottles and can be kept for several months.

In the next step, the two liquids are poured in equal parts into another container. Note that the liquid is sensitive to light from the moment it is mixed. However, the liquid only reacts with UV light. Dimmed candlelight, artificial light with low UV or a red light lamp can be used safely. The liquid has an intense yellow color when unexposed. It is not advisable to store the light-sensitive liquid for long periods. Only the quantity required for use should be mixed.

The light-sensitive liquid can now be applied to paper, fabric or wood, for example. Any surface that absorbs water is suitable. Make sure that the liquid is applied as thinly as possible. If it is applied too thickly, this will lead to blurred results or will not adhere to the surface. Flat hair brushes, sponge brushes or absorbent cotton can be used for this purpose.

The motifs to be exposed can come from a wide variety of sources. Digital photos can be converted into a negative and printed on film. Analog negatives can also be exposed. Another possibility is to expose objects. Semi-transparent objects such as flower petals, feathers, fabrics, etc. are particularly exciting. This option in particular invites you to experiment. Different layers can also be combined and worked with like a collage.

The chosen motif is then placed on coated paper (or wood, fabric, …). Both are then covered with a sheet of glass. To ensure that the motif lies as flat as possible on the surface, the glass is weighted down. There must be no gap between the subject and the background, otherwise the light will find its way into this space and cause blurring. For those experienced in the darkroom: this is a contact print. The subject has direct contact with the background to be exposed.

Exposure can then take place in the sun or under a UV lamp. Exposure in the sun is less easy to plan and repeat, which is why it is advisable to use a UV lamp when creating a production »print«. Exposure tests should always be carried out in order to achieve an ideal result. Every material and every motif requires different exposure times. Wood, for example, generally takes longer to expose than paper.

When the exposure is complete, it is finished with a simple water bath. The still sensitive particles of the emulsion are rinsed off and do not adhere to the substrate. The particles of the emulsion that have come into contact with UV light are colored blue and adhere to the substrate. This means that the black, opaque areas of the motif are rinsed white in the final print.

The blue coloration is radiant after soaking and darkens a little later. Contrasts become even stronger when drying and many details appear that were thought to be lost. Various substances such as black tea or coffee can be used to color the blue prints and change them in a sepia direction, for example.

History

The cyanotype was discovered around 1840 by the English chemist and photographer John Herschel. It was initially used to reproduce construction plans. The so-called blueprints.

One of the world’s first female photographers – Anna Atkins – published the first book that was illustrated exclusively with photographs as early as 1843/44. She used the appealing technique of analog photography: the cyanotype.

Signing of prints

according to the »rules« by Lothar Lang, Der Graphiksammler, Berlin 1979

On the left side under the print, prints before the edition are marked with Roman numerals, possibly also as a proof = E.E., or as a proof for the artist (number = 10% of the edition size) = e.a./E.A. = Épreuves d’artiste = A.P., or outside the sale = h.c. = hors commerce; the edition, if the printing sequence is known, is marked as a fraction, with the serial number in the numerator and the edition number in the denominator. (Otherwise always 1–number of print run).

On the right is the signature and the date of creation, in the center a possible title and/or cycle. Sometimes the technique is also noted here.