Historical Context
Invented by Frederick Scott Archer in 1851, wet plate collodion dominated photography from the 1850s through the 1880s. The process produces negatives or direct positive images (ambrotypes on glass, tintypes on metal) with extraordinary detail and tonal range. The "wet" designation refers to the requirement that the plate must be exposed and processed while the collodion remains moist.
Chemistry
Salted Collodion
Base collodion (2% solution):
| Component | Amount |
|---|---|
| USP collodion | 280 ml |
| Or: Ether | 180 ml |
| Ethyl alcohol | 90 ml |
| Gun cotton (pyroxylin) | 5.5 g |
Salts (dissolved separately before adding to collodion):
| Component | Amount |
|---|---|
| Potassium iodide | 2 g |
| Cadmium bromide or potassium bromide | 1.5 g |
| Distilled water | 3 ml (each) |
Add salts slowly to collodion while stirring. Age 1-2 weeks before use.
Silver Bath
| Component | Amount |
|---|---|
| Silver nitrate | 45-50 g |
| Distilled water | 500 ml |
Add a few drops of nitric acid to clear the bath if it clouds. The bath should be maintained at approximately 8-10% silver content.
Developer
| Component | Amount |
|---|---|
| Ferrous sulfate (iron sulfate) | 15-20 g |
| Glacial acetic acid | 15-20 ml |
| Ethyl alcohol | 15-20 ml |
| Distilled water | 500 ml |
Fixer
| Component | Amount |
|---|---|
| Sodium thiosulfate | 150 g |
| Water | 1 litre |
Or use potassium cyanide fixer (more effective but extremely hazardous—see safety notes).
Procedure
-
Clean plate: Glass must be absolutely clean. Clean with whiting or rottenstone, then rinse with alcohol.
-
Pour collodion: Under safelight, pour salted collodion onto plate, tilting to coat evenly. Allow excess to drain back into bottle. Coating should appear even with no holes or thin spots.
-
Sensitise: Before collodion fully sets (while still tacky), lower plate into silver bath. Sensitise for 3-5 minutes depending on conditions.
-
Load and expose: In safelight, remove plate from silver bath, drain briefly, and load into plate holder. Expose immediately—plates lose sensitivity rapidly.
-
Develop: Pour developer over plate. Image appears within seconds. Development continues for 15-30 seconds depending on exposure.
-
Fix: Rinse briefly with water, then fix in sodium thiosulfate until milky appearance clears (1-3 minutes).
-
Wash: Thorough water wash.
-
Varnish: Once dry, plates should be varnished to protect the delicate collodion surface.
Ambrotypes vs Tintypes
Ambrotype
- Underexposed negative on clear glass
- Appears positive when backed with black velvet, paper, or varnish
- Glass must be clean and properly prepared
- More fragile
Tintype (Ferrotype)
- Collodion on black japanned iron plate
- Direct positive image
- More durable than ambrotype but surface still delicate
- Characteristic dark appearance
Working with Wet Plate
The "wet" in wet plate is critical:
- Plates must be exposed while still damp
- Working time is typically 10-15 minutes depending on temperature and humidity
- Hot, dry conditions shorten working time dramatically
- Plates cannot be stored—each must be prepared immediately before exposure
Troubleshooting
| Problem | Likely Cause | Solution |
|---|---|---|
| Fogging | Light leak; contaminated silver bath | Check darkroom; test/filter silver bath |
| Oyster marks | Plate dried during sensitisation | Work faster; increase humidity |
| Pinholes | Contamination in collodion | Filter collodion; clean pour bottle |
| Low sensitivity | Exhausted silver bath; old collodion | Maintain bath at 8-10%; use fresh collodion |
Safety
| Chemical | Hazard | Precautions |
|---|---|---|
| Ether | Extremely flammable; anaesthetic | No flames; excellent ventilation; fire extinguisher nearby |
| Collodion | Extremely flammable | Same precautions as ether |
| Silver nitrate | Corrosive; stains | Gloves essential |
| Ferrous sulfate | Low toxicity | Standard precautions |
| Potassium cyanide | EXTREMELY TOXIC — LETHAL | Not recommended for amateur use |
| Cadmium bromide | Toxic; carcinogenic | Gloves; avoid inhalation |
Fire Warning
Ether and collodion are extremely flammable. Never work near open flames, sparks, or heat sources. Have appropriate fire extinguisher nearby. Work in well-ventilated areas to prevent ether accumulation.
Cyanide Warning
Potassium cyanide is sometimes used as a fixer for wet plate and for cleaning silver baths. It is EXTREMELY TOXIC—exposure can be fatal. Amateur use is strongly discouraged. If you must use cyanide, ensure you have appropriate training, ventilation, and emergency procedures. Never acidify cyanide solutions—this releases deadly hydrogen cyanide gas.
Further Reading
Quinn Jacobson, Chemical Pictures: The Wet Plate Collodion Book: Making Ambrotypes, Tintypes & Alumitypes (CreateSpace, 2013) The comprehensive guide to the wet plate process. Later editions (2019/2020) include access to video workshop content. The definitive reference for contemporary wet plate practitioners.
Christopher James, The Book of Alternative Photographic Processes, 3rd Edition (Cengage Learning, 2015) The definitive comprehensive text on alternative processes, with detailed coverage of wet plate collodion.
Jill Enfield, Jill Enfield's Guide to Photographic Alternative Processes, 2nd Edition (Routledge, 2020) Covers wet plate alongside other historical processes, with practical guidance.
The Light Farm (thelightfarm.com) Online resource for DIY emulsion making, with information relevant to understanding collodion chemistry.