The inherent problem of the iron-based silver processes lies in the danger of leaving residual ferric iron in the print, to its eventual undoing as the image is attacked. The Argyrotype process, developed by Mike Ware, has been designed to avert this problem, and ingeniously uses a little known silver salt, silver sulphamate, manufactured ‘in-situ’. The resulting acidic sensitiser can be washed out of the paper cleanly. Brief working details are included here or you could try the Fotospeed kit.
The Argyrotype sensitiser should be mixed in subdued tungsten lighting, ideally in a darkroom with a safelight.
Dissolve 76mg of sulphamic acid in about 700ml of distilled water at room temperature.
Add in 76mg of powdered silver(1) oxide in small portions, stirring vigorously,Â so that it dissolves over a period of about 20 minutes or so. (Ignore any grey crystals that separate out at this stage.)
Add 23g of ammonium ferric citrate in portions, stirring continuously until dissolved. The solution will appear murky green at this stage. Add 10ml of Tween 20, mixing well, and then add distilled water to make the solution up to 1L.
Filter the solution, and store it in a brown bottle, kept in the dark at room temperature.
Notes on Storage
On storage, the sensitiser may slowly deposit a small amount of black solid. This does not significantly impair its strength, but if troublesome it should be filtered off.
To make a more contrasty sensitiser, an additional 10g of sulphamic acid may be added per litre of solution.
Coating is most easily done using a Coating Rod, spreading the sensiter evenly across the sheet, this should be done in different directions to ensure the whole sheet is covered. Leave to dry. Do not use until completley dry, as wet sensitiser will ruin a negative. Pre-humidifying the paper will give a cooler purple/brown.
Not all papers are suitable, you will have to do some tests to find out which ones work best for you. One of the best is the smooth surfaced Atlantis ‘Silver-Safe’ cotton-fibre paper in 200 g/sq. m. weight.
Printing is by contact, using an Ultra-Violet lamp or sunlight. Exposure time is likely to be 1 or 2 minutes in sunlight, and can be gauged to some extent by the degree of printing-out visible from the front of the contact frame, although a ‘split’ frame is a great help.
Immerse in running water (or 3 or 4 changes of static water) until the yellow background has disappeared. This will take about 5 minutes in running water.
Have a 5% Sodium Thiosulphate (Hypo) solution ready (5g Sodium Thiosulphate to 100m water) for fixing. Immerse in the fixing bath for about 3 mins. The image will cool.
Wash in running water (or static changes) for about 20 mins.
Drain and air dry. The image tones will darken, ‘dry-down’, in the drying.
Notes on Fixing
The dilute fixing bath will need replacing frequently. This should be carried out when you find the colour shift from orange to brown becomes sluggish.
Over-exposed prints may be ‘reduced’ by prolonging the fixing time. This also means you should guard against over fixing as the image will start to lighten.
Very delicate gradation in the high values may be obtained by leaving the exposed print in a humid atmosphere (100% R.H.) for about 10 minutes before wet processing.
More detailed instructions can be found on Mike Ware’s Alternative Photography site.