Contact print

A development by Dr. Mike Ware of Kallitype and Van Dyke Brown, Argyrotype produces brown silver prints of subtle graduation on plain artist's paper. The sensitiser, which can last a year or more if correctly stored, should be spread evenly on the print using a glass rod. After a few minutes to allow it to soak in, the print should then be dried for ten minutes at 40C or for half an hour at least at room temperature. A contact printing time of 5-10 minutes under the sun or a good source of UV light is normal. After exposure, develop and clear the print in gently running water for around 5 minutes, and then use a fixing solution for 3 minutes. At this point the colour will intensify, changing from red to a deep brown, which can be turned more blackish-brown by ironing dry at this stage.

Invented by Herschel in 1842, Cyanotype produces characteristic Prussian Blue images through the combination of iron salts with potassium ferricyanide. Once coated, the paper can either be left to dry by air in a darkened room or heat dried with a hair dryer. The image is formed by contact printing using the sun, but because the process cannot resolve fine detail, working from a line negative is recommended. Once exposure is complete, wash the print in cold running water for around 30 minutes until all yellow is gone. To brighten the highlights, rinse the print briefly in a dilute chlorine bleach bath, or to lighten specific areas, use a brush and bleach diluted 1:32. As well as paper, Cyanotype prints can be made onto heavy cotton or canvas, but you should avoid exposing finished images to bright light, or they will fade.

The "brown" in the name of this process gives you some idea of the colour of the finished print -although tones tend to be delicate rather than heavy - so clear, graphic images tend to work best.The process involves combining iron salts with silver nitrate and either oxalic acid for a warm-brown colour or tartaric acid for brown-black result. Tightly-woven fabrics can be a better base than paper, as the finished "print" must be washed in water. Exposure is by contact printing, but, because of the relatively high sensitivity of the medium to light, you should work in dim conditions, and give an exposure of around 1 minute in sunlight.Develop the image in a 1% borax solution, fix it in traditional hypo, and give a final wash of at least 30 minutes.