St Pauls Photography, Bristol
Invented by William Henry Fox Talbot, c. 1834 — the first modern photographic process
Notes from the video tutorial by St Pauls Photography
The salt print was invented by William Henry Fox Talbot of Lacock Abbey and is the first of the modern photographic processes. It predates the albumen print and produces a softer, more matte surface. By the 1860s it had largely been superseded by albumen printing, though both processes use silver nitrate sensitisation and are fixed with sodium thiosulfate.
| Item | Notes |
|---|---|
| Acid-free watercolour paper | The process is sensitive to paper quality |
| Salt solution, 2% | Photographic grade or pure sea salt; not ordinary table salt |
| Silver nitrate solution, 12% | With citric acid as preservative; store in a brown bottle |
| Sodium thiosulfate (‘hypo’) | Classic photographic fixer |
| Negative | For contact printing |
| Clip-frame or UV box | For exposure |
Mark the back of the paper with a pencil. You will salt one side and sensitise the same side — salting the front and sensitising the back will produce no image.
Pour 2% salt solution into a shallow tray. Arch the sheet of paper slightly and drop it face-down onto the surface of the liquid. Do not push it under — you only want a thin layer of salt on the surface, not a soaked sheet.
Leave it to float. The edges will begin to curl upward; when they have lifted about a quarter of an inch, the paper is ready.
Lift the paper by one corner, let it drain, and check the coating by rocking it in reflected light — a nice even gloss means an even coat.
Dry the paper thoroughly before sensitising.
Add a second pencil mark (a cross) on the back of the paper so you know it has been both salted and sensitised.
Apply the 12% silver nitrate solution using either the brush or rod technique. The solution is clear, so work carefully and use reflected light to check for even coverage. Leave a small margin around the edges to handle the paper.
Dry the sensitised paper. Work quickly — the salt print is more light-sensitive than the cyanotype and should not be left out unnecessarily.
Dip only the tip of the brush into the silver nitrate. Brush evenly across the paper, checking in reflected light as you go. Produces a slightly uneven, textured surface that some find attractive.
Clamp the paper to a board. Lay the rod at the base, run a thin bead of solution into the angle between rod and paper, then draw the rod smoothly up the sheet in one continuous action. Gives a smoother, more even coat — recommended for printing from negatives.
Place the negative on top of the sensitised paper (sensitised side up), cover with glass, and secure in a clip-frame with elastic bands.
Expose in bright sunlight for approximately 6 minutes; longer if overcast. The print will appear very dark when correctly exposed — it lightens significantly in the wash and fix.
Salt prints can also be used to make photograms by laying objects (feathers, leaves, etc.) directly onto the sensitised paper under glass.
A split-back contact printing frame is useful for checking exposure mid-way without allowing the negative and paper to slip out of register.
First wash: Place the print in running water for 4–5 minutes to wash out the unreacted sodium chloride and silver nitrate. The print will lighten considerably.
Fix: Transfer to sodium thiosulfate (‘hypo’) fixer and rock gently to and fro for 4–5 minutes. This dissolves out all the unexposed silver chloride. The print will shift colour slightly — this is expected. Do not use modern rapid fixers — they are too aggressive.
Second wash: Return to running water for 4–5 minutes to remove all fixer. Dry flat. Much of any apparent unevenness in the coating disappears as the print dries.
Always mark the back of the paper before starting — salt and sensitise the same side or the process will not work.
Use photographic-grade or pure sea salt. Ordinary table salt (which contains anti-caking agents) is not suitable.
Use separate syringes and brushes for each chemical. Cross-contamination between processes (e.g. cyanotype and salt print) will cause problems.
Silver nitrate will turn skin black within 24 hours. It is not dangerous but takes weeks to fade. Wear gloves when sensitising. Historically it was known as lunar caustic and was used to remove warts.
If you do not fix the print, the image will eventually turn brown and be lost entirely.