Photographic Printing, How to Create a Real Salt Print
How to Make a Real Salt Print
The major breakthrough in the development of the modern photographic process came in 1835, when William Henry Fox Talbot, F.R.S. had a eureka moment and realised how to produce, on a support, silver chloride, the silver halide he needed for crisp, clear photographic prints. Some have suggested that moment came in 1833 when on his honeymoon!
Unlike the cyanotype process, salt printing is not cheap, although not as expensive as platinum printing; it is safe when adhering to strict chemical safety processes.
Remember the safety precautions with chemicals, rubber gloves, goggles, don’t get chemicals in your mouth, wash your hands, don’t work on food preparation surfaces; don’t eat, drink or smoke whilst using chemicals, most importantly:
it is definitely not for children.
As one would expect, salt (sodium chloride) is one of the chemicals required; however, ordinary table salt won’t do as it contains anti-caking chemicals that will interfere with the process, the best salt to use is sea salt or cooking salt, some use seawater.
Silver nitrate is the light sensitive chemical needed, but it only produces a thin, grey image, what is needed is silver chloride, but that has no solvent to allow coating on to a support. In a flash of inspiration, Talbot came up with an elegant solution to the problem and gave us negative/positive photography.
Silver nitrate is toxic if swallowed, corrosive, and stains.
Citric acid is needed as a preservative for the silver nitrate solution.
Use Hypo (sodium thiosulphate)to fix your print, not general photographic fixer, which is too aggressive and will bleach your print.
Sodium carbonate (washing soda) to make the hypo more alkaline.
Like cyanotype, salt printing is a contact print process, so the main disadvantage is obtaining large enough negatives. I use a 5x4 film camera and contact print from the negatives it produces. If you have a 35mm or medium format camera, you will need to scan, or get scanned, the negatives to print out large negatives on overhead projection film (OHP). If you have a digital camera, the chances are you already have image editing software on your computer to create negatives with OHP film. It is possible to make negatives on ordinary writing paper, Talbot made his by putting sensitised paper into his camera, of course, we use an inkjet printer to print our scanned neg.
The method, and that elegant solution:
You first need to salt the paper; cheap drawing paper will do as long as it is strong enough to be soaked. I use Saunders Waterford 140 lb watercolour paper, hot pressed or NOT (cold pressed) surface. Mix 20grams of salt with 1 litre of tap water to make a 2% solution. Pour this into a watertight tray large enough to take the paper size you’re using.
Put a small mark on the back of the paper and then soak the paper by immersion; dry the paper with a hair dryer. This operation can be done in normal light.
In a graduated chemical measure, mix 12g of silver nitrate with 50 ml of distilled/purified/de-ionised water, NOT tap water, the solution will react with the chemicals the water authorities add to the water. Keep to one side. In another chemical measure, mix 6g of citric acid crystals with 50ml of distilled/purified/de-ionised water, when they are both fully dissolved, mix them together and store in a labelled, brown bottle. Pour a small amount of this liquid into an old, never again to be used for food purposes, saucer and brush on to the front of the salted paper. Dry the emulsion off with a hair dryer and tape to it, along one edge, your negative, sandwich this between a piece of hardboard and a sheet of glass, fixing with bulldog clips. The whole operation to this point with the silver nitrate is carried out under normal tungsten lighting or daylight with the room curtains closed, no fluorescent tubes or TV light.
You now have on your paper:
The chemicals will react and give you:
Clever wasn’t he?
Put in the sun, or in front of a UV light source, and check by unclipping and lifting your negative, say, every three minutes until the tones look right.
Wash/develop the print under running water for about five minutes, until the water turns from milky and runs clear.
Fix in a mixture of 25g sodium thiosulphate, 2g sodium carbonate and 500ml tap water.
Wash for half an hour.
Like cyanotype, salt prints are as permanent as the support the are printed on.
I have no control over how you may carry out these operations, as I said earlier, it is not for children and silver nitrate is a hazardous chemical, you are responsible for your own safety.