Historical Context
Salt printing was the first paper-based photographic process, developed by William Henry Fox Talbot from 1834 and made public in 1839. Plain salted paper was almost universal for positive prints in the 1840s; albumen paper, introduced in 1850, displaced it during the 1850s.
Chemistry
Salt Bath (for sizing paper)
| Component | Amount |
|---|---|
| Sodium chloride (table salt) | 20 g |
| Gelatin (optional sizing agent) | 2 g |
| Water | 1 litre |
Silver Bath (sensitiser)
| Component | Amount |
|---|---|
| Silver nitrate | 120 g (a 12% bath) |
| Distilled water | to 1 litre |
| Citric acid (optional preservative) | 10-50 g (1-5%) |
Reilly recommends starting with a 12% bath and keeping it between 10% and 12%. Sensitise for about 3 minutes. Citric acid at 1% noticeably extends the bath's life; 5% gives the maximum preservative effect.
Alternative Two-Step Method
Some practitioners prefer separate sizing and sensitising steps:
Step 1 — Salt solution:
| Component | Amount |
|---|---|
| Sodium chloride | 20 g |
| Distilled water | 1 litre |
Step 2 — Silver solution:
| Component | Amount |
|---|---|
| Silver nitrate | 120 g |
| Distilled water | to 1 litre |
Procedure
-
Paper preparation: Select smooth, hot-pressed paper. Paper can be sized with gelatin or used unsized for softer results.
-
Salting: Float or brush paper in salt solution. Allow to dry thoroughly.
-
Sensitising: Under subdued light, float or brush salted paper in silver nitrate solution. Dry in darkness.
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Exposure: Contact print under UV light (sunlight is traditional). This is a printing-out process—expose until shadows are distinctly darker than desired (exposure will reduce in fixing).
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First wash and toning: Wash in several changes of water to remove the free silver nitrate, then gold tone (see Gold Toning below) and wash for 5 minutes. Gold toning must be done before fixing.
-
Fixing: Fix in fresh alkaline sodium thiosulfate, using two trays:
Component Amount Sodium thiosulfate (pentahydrate) 150 g Sodium carbonate 2 g Water 1 litre Fix for 4 minutes in each bath with constant agitation. Prolonged fixing is harmful: thiosulfate soaks into the paper fibres and becomes hard to wash out.
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Washing: Rinse for 2-4 minutes, treat in 1% sodium sulfite for 3-4 minutes, then wash for 30 minutes.
-
Drying: Hang or lay flat to dry.
Gold Toning for Salt Prints
Alkaline gold toner (produces purple-brown tones). Use it after the first wash and before fixing. This is Reilly's borax toner; he gives 0.1-0.2 g of gold chloride per litre for matte salted paper (10-20 ml of a 1% solution) and uses 40 ml for glossy albumen:
| Component | Amount |
|---|---|
| Borax (sodium borate) | 10 g |
| Gold chloride (1% solution) | 10-20 ml |
| Distilled water | to 1 litre |
Tone at 17-20 °C with constant agitation for 3-15 minutes, depending on paper and conditions, then wash for 5 minutes in running water before fixing. Bostick & Sullivan sell a ready-made thiocyanate gold toning kit (see the Van Dyke Brown guide for its formula). Untoned salt prints fade significantly; gold toning is highly recommended for permanence.
Paper Selection
Salt printing works best on smooth, well-sized papers:
- Hot-pressed watercolour papers
- Bergger COT 320
- Arches Platine
- Hahnemühle Platinum Rag
The paper surface significantly affects the final appearance—smoother papers produce finer detail, while rougher papers create a softer, more atmospheric look.
Troubleshooting
| Problem | Likely Cause | Solution |
|---|---|---|
| Weak image | Under-salting; weak silver bath | Increase salt/silver concentration |
| Mottled appearance | Uneven salting or sensitising | Improve floating/brushing technique |
| Fading | Exhausted fixer or poor washing; no toning | Fix in two fresh baths; wash thoroughly; gold tone before fixing |
| Staining | Contaminated chemicals; insufficient washing | Use fresh solutions; extend washing |
Safety
| Chemical | Hazard | Precautions |
|---|---|---|
| Silver nitrate | Causes severe skin burns and eye damage; oxidiser; very toxic to aquatic life | Gloves and eye protection essential; keep away from combustible materials; do not pour down the drain. Black skin stains are not permanent and wear off as the skin renews |
| Sodium thiosulfate | Low toxicity | Standard precautions |
| Gold chloride | Corrosive: causes skin burns and eye damage; may cause an allergic skin reaction; harmful if swallowed | Gloves and eye protection |
| Sodium carbonate (fixer) | Causes serious eye irritation | Eye protection |
| Borax (gold toner) | Danger: may damage fertility or the unborn child (Repr. 1B, H360FD); on the REACH Candidate List | Gloves; avoid dust; keep away from anyone pregnant or trying to conceive |
| Citric acid | Causes serious eye irritation; may irritate the airways | Eye protection |
Further Reading
Christina Z. Anderson, Salted Paper Printing: A Step-by-Step Manual Highlighting Contemporary Artists (Routledge, 2017) Part of the Contemporary Practices series. Covers photogenic drawing through advanced methods, animal-friendly alternatives, toning, and combination printing. The definitive modern reference for salt printing.
Christopher James, The Book of Alternative Photographic Processes, 3rd Edition (Cengage Learning, 2015) The definitive comprehensive text on alternative processes, with detailed coverage of salt printing including historical context and practical guidance.
Jill Enfield, Jill Enfield's Guide to Photographic Alternative Processes, 2nd Edition (Routledge, 2020) Covers historical roots through digital manipulation, with practical salt printing instruction.
Sources
- The Albumen & Salted Paper Book, ch. 3: Salted Papers, James M. Reilly (CoOL / AIC)
- The Albumen & Salted Paper Book, ch. 6: Sensitization, James M. Reilly (CoOL / AIC)
- The Albumen & Salted Paper Book, ch. 8: Toning, James M. Reilly (CoOL / AIC)
- The Albumen & Salted Paper Book, ch. 9: Fixation and Washing, James M. Reilly (CoOL / AIC)
- Gold Toning Kit instructions (POP, Van Dyke, kallitype, albumen and salt prints), Bostick & Sullivan
- Silver nitrate substance information, ECHA