Graphite and silver nitrate

Clive Heritage-Tilley describes some interesting printmaking techniques using mixed media with historic photographic chemistry.

Graphite and silver nitrate

Digital photography now replaces most of the chemical and physical applications that chemical photography employed over its relatively short history of about 170 years. The colour and form of a digital image after capture in the camera and if desired manipulation through Photoshop, allow the photographer an exacting control over the finished image, with little if nothing left to chance and with the ability to reproduce numerous identical copies.

In the early development of chemical photography, individual images were more unique in there nature, as a silver image produces something that is far more difficult to control and exhibits a more random nature from chemical reaction. This is particularly the case when the print maker is controlling the chemistry and exposure. Early photographic chemistry can exhibit enormous variations in reaction to colour, sensitivity and stability, making the visual outcome unique and often unrepeatable.

By experimenting with some of these more antiquated processes, it is possible to produce these on paper without the need for a suspension medium such as gelatine. Thus, to use the chemistry as a printmaking medium and together with others, such as ink and graphite. The development of digital photography has therefore helped establish this chemical art form in its rightful place within the context of printmaking.

Printmaking

To explore the fascinating possibilities, it is necessary to look back at the dawn of photography and some of the experiments made by practitioners working at that time. Robert Hunt who experimented with light sensitive substances, in his “Researches on Light in its chemical reactions” published in 1844, points out many interesting reactions of substances with light, including charcoal:

“ If a stick of charcoal is placed in a bottle in which is some solution of nitrate of silver, so that one half of the charcoal is in the solution, and the other half above it, there will in a short time appear little spangles of silver upon the upper portion of the charcoal, if it is exposed to diffused light. In full sunshine the effect is greatly retarded. If the bottle is placed in a dimly illuminated place, there will in the course of a few weeks, form in the solution around the charcoal, a series of the most delicate thread-like crystallisations of the silver. After these have formed, if the bottle is exposed to sunshine they are gradually re-dissolved into the fluid.”

There is still much to be learnt by looking in depth at the work of these experimenters and reactions they dismissed at that time, which did not follow the objective of achieving a practical working photographic process. As these may now prove useful when employed in combination with 21st century technology, such as scanning and flash photography, to record precise moments of chemical reaction and decomposition. Let’s bear in mind that technological development and in this case chemical discoveries, are not always in step with chronological progression.

Fox Talbot who developed the first real practical form of photography, employing a negative and positive, used the word Calotype to describe his process, which is derived from the Greek word Kalos, meaning beautiful. Looking at some of the early examples, beautiful is surely a very apt word.

Basically the process relies on coating paper with Silver Nitrate and then Potassium Iodide, thus creating light sensitive Silver Iodide, with the Potassium nitrate then being washed out. The original Calotype negatives were made on writing paper and if stored carefully, they could be kept for some time. Just as with many of the printing-out processes, the image was composed of fine particles of metallic silver within the surface fibers of the paper and not in an emulsion.

To use paper as a base for a negative has various problems, as it can vary slightly in thickness at different areas and patches undetectable when looked at by reflected light become visible when viewed by transmitted light. A solution of silver nitrate and Gallic acid was then coated onto the iodized paper in very dim lighting conditions, partially dried and as it was more sensitive when moist, it was then exposed in the camera, sometimes for as little as a few seconds. The latent image could then be developed using a fresh solution of Gallo-Nitrate of silver until it was deemed correctly developed. It was then fixed with a solution of Sodium Thiosulphate, washed and dried.

When these negatives were originally produced it was sometimes common practice to retouch them in pencil. A process which could be carried further today by using other mediums such as graphite and ink in order to produce a negative photo drawing. A calotype paper negative lends itself very nicely to such intervention. Prints could also be made using this same Calotype process, but a more usual practice in the early stages was to print using Talbot’s paper salted process. These could then be fixed again using Sodium Thiosulphate, although a nicer image quality could be obtained using Talbot’s stabilization process, namely strong salt solution.

Graphite print

The Van Dyke process is similar to the Calotype, but a simpler technique to work with and therefore one which could be used as a starting point and the method for which is outlined in the following steps:

Note – Please wear gloves and consult the chemical health and safety data before handling chemicals. Also be aware that when making reference to formulae or method, there are a number of critical factors that may affect the results. These can include the temperature of working solutions, humidity and if you are not using distilled water the ph of tap water may vary slightly from place to place. It is therefore a good idea to try and use these merely as a guide and try to grasp the general principles involved, as this will allow a process of individual self discovery.

The following formula may be used as a starting point to make 300ml of sensitizing solution:

1Mixing the chemicals
Mix 30gm of Ferric Ammonium Citrate with 80ml of distilled water (these first 3 steps can be done in normal ambient lighting).

2Mix 5gm of Tartaric acid crystals with 80ml of water.

3Mix these 2 solutions together to give you 160ml of mixed solution.

4In subdued lighting mix 12gm of silver nitrate in 80ml of distilled water.

5Still in subdued lighting, add the silver nitrate solution to your mixed solution, a few drops at a time and stirring constantly to avoid creating a precipitate.

6Finally top up with another 60ml of distilled water to make the final 300ml of solution and store in a dark bottle out of the light, perhaps rapped in a black plastic bag. Before using this solution, it should be allowed to age for a few days and the bottle shaken occasionally.
 
As the sensitising solution is primarily U.V. sensitive, it doesn’t lend itself to direct production using a projected image, but requires an intermediate neg/pos medium for direct contact printing, either in sunlight or with the use of a U.V. light source.
 
Mixing historical and digital photography
Positive made from original negative and then reverted back to negative at full size on lithographic film.
 
The origination of the image to be used could be digital or chemical, although if using digital it will be necessary to convert this to film, such as lithographic neg/pos for printing purposes.
 
The selection of a suitable paper will be one which has sufficient wet strength, as it needs to withstand immersion in chemical solutions without disintegrating. The prints shown here are made on a quality hot press paper surface, which due to its art surface finish also helps improve sharpness. A variety of materials lend themselves to coating and experiments will soon establish what works well.
 
On these prints, graphite and ink underneath the coating have been applied, which allows them only to come through when the image density is less than the media beneath. If you wished to do this on top of the image the effect would be quite different and this affects how the final image will look in relation to the way it is coated. If the original negatives are made by projection, it is also possible to project the same image at the same size that the contact films are made onto the paper to be coated. This would allow sketching or shading into visible same size areas of the picture. Such intervention could have many possibilities, as the light sensitive coating could be applied only to areas where a photographic part or whole image is required.

7Coating the paper
The Ambient lighting used for coating the paper is quite important and you may want to strike a balance between being able to see what’s happening and any pre-exposure effect. Here, a light box with an amber tint over the top was used. There are many ways you can apply the sensitizer such as brush or by glass rod, but here it has been applied using a small sponge. This allows excess liquid to be picked up after the coating has been completed, thus mopping up any areas with excess solution. Also, by keeping the coating thin, it allows any media applied first to show through.

8Exposure
As previously stated Van Dyke Brown solution is primarily UV sensitive and about 20 minutes in bright sunshine should produce a suitable image, dependent of course on the negative density. A series of test exposures under a glass frame arrangement can provide a good indication of final exposure time.

Silver nitrate printmaking

Processing – After exposure the print can be placed in a tray of water, containing about a tablespoon of borax per litre and soaked for about five minutes (at this stage it will be a yellowish colour). It can then be washed in running water for about 10 minutes, followed by a few minutes fix in a 2% solution of Sodium Thiosulphate (this will turn it to a nice deep brown). The paper can then be washed in running water for about 30 minutes and hung up to dry. As the print dries it will darken and this needs to be taken into consideration at the printing stage.

Such early photographic chemistry lends itself nicely to this printmaking technique.




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