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Argyrotype processing - The complete guide to Argyrotype with our host, Dr Mike Ware
Words Dr Mike Ware
Please refer to the previous article Preparations to Alternative Printing which has an explanation of what's needed and how to prepare to make an Argyrotype print
Sensitizer chemicals needed
(General Purpose Reagent Grade - ca. 98% purity - is adequate.)
- Sulphamic acid NH2SO3H (spelt 'sulfamic' in USA) 7g
- Silver(I) oxide Ag2O (or see alternatives below) 7g
- Ammonium iron(III) citrate (the 'green' form) 22g
- Tween 20(tm) (non-ionic surfactant) 0.2-0.5cc
- Distilled water, to make 100cc
Making up Argyrotype Sensitizer (Under tungsten light, not daylight.)
1 Heat 70cc of distilled water to ca. 50C; dissolve in it 7g of sulphamic acid.
2 Add 7g of powdered silver(I) oxide to the hot solution (1) in small amounts with vigorous stirring until all is dissolved.
3 Add 22g of green ammonium iron(III) citrate to the warm solution in portions, with stirring, until it is all dissolved. Allow to cool.
4 Add 0.2 to 0.5cc of Tween 20 and mix well. (The appropriate quantity of this wetting agent is variable and will depend on the paper used. You may prefer not to add it to the stock sensitizer, but keep a separate solution - see below.)
5 Add distilled water (at room temperature) to make a final volume of 100cc and filter the solution to remove any remaining solid. (The solution should be a clear deep olive-green colour.)
6 Store in a brown bottle in the dark at room temperature. (The solution should keep for a year, at least. If it throws down a small amount of black precipitate, it should be re-filtered.)
Option To make a more contrasty sensitizer, add an extra 1g of sulphamic acid.
Caution This solution is irritant and will stain skin and fabrics: wash away spillages with plenty of cold water.
Some alternatives in the chemistry
- 7g of silver(I) oxide may be prepared by adding a solution of 2.5g of sodium hydroxide dissolved in ca. 20cc distilled water to a solution of 10.3g of silver nitrate in ca. 30cc distilled water. Filter off and wash the precipitate. It may be dissolved in the sulphamic acid while still moist.
- Alternatively, 8.4g of silver carbonate may be used instead of silver oxide; but it should be dissolved at room temperature in a tall vessel - a 250 or 500cc measuring cylinder to contain the spray; adding the silver carbonate in small portions, and allowing the effervescence to die down each time.
- If you prefer to avoid the difficulties of obtaining and manipulating the chemicals, then ready made-up Argyrotype sensitizer solution can be purchased from Fotospeed.
- The wetting agent, Tween 20, is included in the formulation to assist uptake of the sensitizer by the cellulose fibres. It minimises bleeding of the colloidal metal image during processing, but may penetrate some papers unevenly, causing blotchiness or granularity in those that contain a mixture of fibres, or staining in those that are gelatin-sized. The appropriate amount to use can be fine-tuned by keeping a separate stock solution of strength 20% v/v, and adding one or two drops per 5cc of sensitizer before coating, so that its final concentration is around 0.2 to 0.5%.
Choice of Paper
Your choice of paper is critical because its purity is crucial to the success of this process. Only the best cotton fibre, internally sized with Aquapel and free of other additives, will do. Particularly recommended are:
* Ruscombe Mill's handmade 'Buxton' paper
* Whatman's Watercolour
* Saunder's Somerset
* Atlantis Silversafe Photostore
* Crane's Platinotype or 'Parchment Wove'.
If a glass rod spreader is used, a 10x8in coat requires about 1.5cc of sensitizer, depending on the paper and Tween concentration. Brush coating will consume more.
Allow a few minutes for the sensitizer to soak in, until the paper surface appears non-reflective, then dry for about 10 minutes in a stream of warm (40C) air. Alternatively, simply allow it to dry at room temperature and humidity, in the dark, for about an hour. The sensitized paper should preferably be used within a few hours. If longer term storage is desired, a desiccated box, containing silica gel or anhydrous calcium chloride, should be used: storage life in a dry environment can be many weeks.
For full details of how to prepare the frame for printing click here.
As with other iron-based printing processes, a negative with a long density range (fb+f to 2.2) is desirable. Softer negatives, with a range of 1.5 or so, may be accommodated by using the more contrasty sensitizer recipe, with additional sulphamic acid. By mixing the two formulations, the contrast of the sensitizer can be fine-tuned.
Printing is by contact, using a UVA source or the sun. Exposure will be similar to other iron-based processes, in the order of five minutes to an average light source.
If the relative humidity of the paper is 'normal' (i.e. dried at an ambient RH between 40% and 80%), a detailed print-out image will be obtained, orange-brown on a yellow background, which with experience gives a good indication of correct exposure, making test strips unnecessary. A little development can subsequently be expected to occur in the high values during wet processing, and the colour will darken to a rich brown; there will also be considerable 'drying-down' of the tonality. All these factors should be taken into account in judging exposure by inspection. It is better to overexpose than underexpose, because a dense image can be reduced.
The colour of the print-out image may be shifted to a more neutral tone - an attractive purplish-grey - if the sensitized paper is humidified before exposure by leaving it above the surface of water (100% RH) for 20-30 minutes in a closed container at room temperature. This is a very economical method of colour control! A word of caution though: humidified sensitized paper can damage negatives during contact printing unless a protective layer of polyester film is interposed between the two; this must be very thin, or it may worsen the sharpness of the image.
This is extremely simple and non-critical, requiring only pure water and one inexpensive 'fixer' solution, 2% sodium thiosulphate, prepared by dissolving ca. 20g of the crystals in 1litre of water. This bath has a capacity of about ten 10x8in prints and should be replaced when necessary.
It is very important to avoid using chlorinated water. Your running tapwater may be unsuitable for this initial wash, if it changes the image colour from orange-brown to a dirty buff. A static bath of pure water, replaced three times, should suffice. The pure water can be distilled, de-ionised, reverse-osmosed, carbon filtered, or simply, rainwater.
The yellow unexposed sensitizer of excess iron and silver salts should completely wash out in this bath. If there is any bleeding of colloidal silver metal, indicated by a red-brown stain running off dense areas of the image, then the paper fibres are failing to trap the tiny silver particles, and it is likely that insufficient Tween has been used, or that the paper is unsuitable. The effects of bleeding may be minimised by processing the print face down, to avoid staining adjacent areas, but there will be some density loss.
If a particularly long tonal range is desired with very delicate high value gradation, the exposed print should be left in a humid atmosphere (100% RH) for ten minutes before wet processing; several steps of highlight detail will build up.
2 Toning bath (optional)
If you wish to tone your print it must be done at this stage, before the fixing. Any of the traditional toning baths for POP or salt prints are suitable: gold, platinum, palladium, selenium, etc.
3 Fix in 2% sodium thiosulphate for 3 minutes
This removes any traces of insoluble silver salts and, if the print has not already been toned, it partially sulphide-tones and intensifies the image, improving the shadow gradation and shifting the colour from red to brown. (As the bath ages its action in this respect increases). Extended treatment in this bath and exposure to air will result in loss of image density especially in the highlights; it may be used to reduce an overexposed print.
4 Wash in running water for 20-30 minutes
At this stage, ordinary tap water, even if chlorinated, should be suitable, especially if the silver image has been protected by toning.
5 Dry at room temperature
The image densities dry down significantly - at least one Zone. Heat drying on a ferrotype plate, or by ironing, can shift the colour to a more neutral blackish-brown, if desired. Unlike silver-gelatine papers, there is no tendency for plain paper prints to curl, and their surfaces are never tacky. Retouching is easily performed on the receptive paper surface with best quality watercolour paints.
Like any colloidal silver image on plain paper, an Argyrotype is inevitably rather susceptible to attack, especially by acids and sulphur-containing substances, so toning is recommended. However, with correct processing, the residual iron and silver in the unexposed areas should be very low, and the image stability and lightfastness are good.
References and further reading
Mike Ware, The Argyrotype Process, British Journal of Photography, vol. 139, no. 6824 (13 June 1991) pp. 17-19.
Mike Ware, Mechanisms of Image Deterioration in Early Photographs - the sensitivity to light of WHF Talbot's halide-fixed images 1834-1844, London: Science Museum and National Museum of Photography, Film & Television, 1994.
John Barnier (Ed.), Coming into Focus: A Step-by-Step Guide to Alternative Photographic Printing Processes, San Francisco: Chronicle Books, 2000
About the author
Dr Mike Ware graduated in chemistry at the University of Oxford (1962) and obtained a doctorate by research in molecular spectroscopy (1965). He became a Chartered Chemist and a Fellow of the Royal Society of Chemistry (1982) and now studies the science, history and art of alternative photographic processes.
Mike acts as a consultant to the National Museum of Photography, Film & Television, Bradford, England, and has supervised postgraduate research in photograph conservation at the Victoria & Albert Museum and the Royal College of Art, and in alternative photographic processes at the University of Derby.
Mike conducts specialist one-to-one workshops and masterclasses in alternative printing techniques throughout the country, and has appeared on BBC Televison in the Open University series The Chemistry of Creativity (1995). Mike also has two books published by the Science Museum, London (or NMSI as it is now known) Mechanisms of Image Deterioration in Early Photographs (1994) and the more recent Cyanotype: the history, science and art of photographic printing in Prussian blue (1999) He is currently working on his third book on Chrysotype.
Contact Mike by e-mail at firstname.lastname@example.org