ARGYROTYPE

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, and we can supply the Fotospeed kit, detailed on this page.

Argyrotype Sensitiser
Chemicals needed. (GPR grade ca 98%)
Sulphamic acid 7.6g. Silver (1) Oxide 7.6 g.
Ammonium Ferric Citrate (green) 23g.
Tween 20 0.8ml (surfactant, assists spreading, poly-oxyethylene sorbitan monolaurate)
Distilled water to make 100 ml.

Procedure for making up
Use subdued tungsten light.
1 Dissolve the sulphamic acid in about 700ml of distilled water at room temperature.
2 Add the powdered silver(1) oxide in small portions with vigorous stirring so that it dissolves over a period of about 20 minutes or so. (Ignore any grey crystals that separate out at this stage.)
3Add the ammonium ferric citrate in portions with continuous stirring until it is dissolved. The solution will appear murky green at this stage.
4 Add the Tween 20, mixing well, and make it up to 100ml. with distilled water.
5 Filter the solution, and store it in a brown bottle, kept in the dark at room temperature.
Notes
1 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.
2To make a more contrasty sensitiser, an additional 10g of sulphamic acid may be added per litre of solution.

COATING & EXPOSURE
Coating is most easily done using a glass rod as spreader as under 'Coating Methods'. Dry thoroughly, as wet sensitiser will ruin a negative. Pre-humidifying the paper will give a cooler purple/brown. Not all papers are suitable, do some tests. 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 Ultra-Violet 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.

ARGYROTYPE PROCESSING
1 Immerse in running water (or 3 or 4 changes of static water) until the yellow background has disappeared, which will take about 5 mins.
2 Immerse in a 2% sodium thiosulphate fixing bath for about 3 mins. The image will cool.
3 Wash in running water (or static changes) for about 20 mins.
4 Drain and air dry. The image tones 'dry-down' somewhat.

NOTES
1 The dilute fixing bath will need replacement frequently. This should be carried out when the colour shift from orange to brown becomes sluggish.
2 Over-exposed prints may be 'reduced' by prolonging the fixing time.
3 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.