Tintype

Historical context

A tintype is a direct positive made by the wet collodion process on a thin sheet of iron coated with dark lacquer ("japanned"). It contains no tin; the name is colloquial, and "ferrotype" refers to the iron. Wikipedia credits Adolphe Alexandre Martin with describing and introducing the process in Paris in 1853, with patents following in 1856 (Hamilton Smith in the United States, William Kloen in the UK). The page carries a "needs more citations" tag and other sources differ over who deserves the credit, so we give no single inventor or year. It was first sold as the melainotype, then the ferrotype, then the tintype.

The Science and Media Museum lists the ferrotype or tintype as a process of about 1855 to the 1940s. It was cheap and quick, and a plate could be prepared, exposed, developed and varnished within minutes. Its widest use was in the 1860s and 1870s, and it survived as a carnival and street novelty. It was revived as a fine-art process in the 21st century.

What it is and how it differs

• A one-off positive. The camera original is a unique image. It is a thin, underexposed collodion negative that reads as a positive against the dark lacquer behind it.
• Mirror-reversed. Camera originals are usually laterally reversed unless a mirror or prism was used.
• Tough. The support is sturdy and light, and needs no protective case. The image layer is durable, though the iron may oxidise at the corners (Wikipedia).
• Same chemistry as the glass processes. Bostick & Sullivan's kit makes tintypes, ambrotypes and glass negatives from a single salted collodion and developer, and recommends beginning with tintypes on black aluminium. The kit's tintype plates are black-coated aluminium rather than iron.

For the shared overview, see wet plate collodion. The glass version is the ambrotype.

Materials and chemistry

Bostick & Sullivan's kit supplies USP collodion, a bromo-iodizer, 10% silver nitrate, a ferrous sulfate developer, an ammonium thiosulfate rapid fixer, sandarac varnish and dilute nitric acid. We give their quantities below. For other formulas, follow the kit or reference instructions.

Salted collodion

Mix collodion and bromo-iodizer in the ratio 25 ml to 40 ml (or 50:80, 125:200, 250:400). The bromo-iodizer is a solution of cadmium bromide, ammonium bromide and potassium iodide in alcohol and ether. Freshly mixed collodion is ready to use at once. As it ages from light yellow to burgundy red, exposure times and contrast increase. Store it in a tightly capped amber bottle below 38 °C.

Silver bath

A fresh bath is 10% silver nitrate (specific gravity 1.08). Bostick & Sullivan add 16 drops of 7% nitric acid per 1000 ml, aiming for about pH 4 (new baths are typically pH 3 to 5). A working bath can fall to 1.04; below that, add silver nitrate crystals a few grams at a time, stopping at 1.06 to 1.07. Filter through a coffee filter.

Developer and fixer

The kit's start-to-finish summary gives 40 to 60 seconds at 20 °C (68 °F) for development, so judge by the plate. Their developer is a traditional ferrous sulfate formulation with a restrainer, so it is hard to overdevelop at 1+3. A litre of working fixer is good for roughly 75 to 100 plates of 8x10 inches.

Procedure

1. Prepare the plate. For black aluminium, peel the plastic layer off the black side. That is all the preparation needed (Bostick & Sullivan).
2. Pour. Collodion is not light sensitive until sensitised, so this can be done in room light, well away from any flame. Pour a generous pool, rock it from corner to corner, drain the excess back into the bottle, then let the solvents evaporate. Suggested times: 30 seconds for 4x5 inches, 45 seconds for 5x7, 60 for 8x10.
3. Sensitise in the silver bath. Lower the plate in quickly to avoid hesitation lines, cover the tank or turn off the lights (yellow and red safelights are fine), and sensitise for 3 to 5 minutes. Drain from one corner for 30 to 45 seconds and wipe the back with a paper towel so silver does not contaminate the plate holder (Bostick & Sullivan).
4. Expose in the plate holder while the plate is still wet. Bostick & Sullivan say exposures vary greatly but are in the 1 to 2 second range in bright sunlight at f/8 or f/11, depending on the subject. Test, and expect the time to change with the collodion's age.
5. Develop at 1+3 for 20 to 30 seconds, then rinse.
6. Fix and wash as above.
7. Dry and varnish. Warm the sandarac varnish in a hot water bath to about 43 °C (110 °F), warm the plate over an alcohol lamp, pour the varnish away from the flame, drain, break the bead of varnish on the edge with a paper towel, then bake it gently until thin wisps of smoke rise (1.5 to 2 minutes). It is dry to handle in about an hour and fully hard after at least a week.

Looking after the silver bath

Bostick & Sullivan call the bath the most important part of the process, and say a well-kept one lasts for years.

• Test the pH after every 30 to 40 plates of 8x10 inches; it should stay near pH 4.
• After roughly 100 to 125 plates of 8x10 inches in 1000 ml, remove built-up alcohol and ether. Either leave the bath in an open wide-mouthed container in bright sun for 48 to 72 hours, then top up with distilled water and filter, or boil it gently for at least 15 minutes on a hotplate in a vessel at least twice its volume.
• Keep animals and children away from the bath while it is sunning.
• Afterwards, re-check pH and specific gravity.

Troubleshooting

Safety

• Ether and collodion. Diethyl ether is extremely flammable, with a flash point of -45 °C and a vapour about 2.6 times as dense as air, so it travels along the ground to a distant flame. It can form explosive peroxides on exposure to light and air (ICSC 0355), and repeated skin contact dries and cracks the skin. Bostick & Sullivan warn that their collodion and bromo-iodizer boil at 95 °F (35 °C). Do not store them near a water heater or pilot light.
• Cadmium bromide, in the bromo-iodizer, is harmful if swallowed, inhaled or in contact with skin and very toxic to aquatic life under its EU harmonised classification (ECHA). NOAA CAMEO Chemicals lists it as a poison (UN 2570); ingestion can cause kidney and liver injury. The harmonised entry does not classify it as a carcinogen, though a few notifiers do. Wear gloves and read the SDS for your kit.
• Nitric acid. Bostick & Sullivan warn that its fumes are extremely irritating to the eyes and lungs and recommend a respirator; the harmonised labelling adds that it is corrosive to the respiratory tract. In the UK it is a regulated explosives precursor above 3% w/w.
• Varnish. Sandarac varnish is highly flammable. Keep it out of the flame while baking, and have a means of extinguishing a burning plate.
• Spent chemistry. Contact your local waste management about disposal. For collodion, Bostick & Sullivan describe evaporating small quantities outdoors, away from buildings; for large amounts, ask your fire department.
• A beginner should work under the supervision of an experienced wet plate photographer (Bostick & Sullivan).

Further reading

Quinn Jacobson, Chemical Pictures: The Wet Plate Collodion Book: Making Ambrotypes, Tintypes & Alumitypes. The standard modern reference.

Christopher James, The Book of Alternative Photographic Processes. Covers wet plate alongside other historical processes.

Sources

• Wet Plate Collodion Kit instructions, Bostick & Sullivan
• Tintype, Wikipedia
• Find out when a photo was taken: collodion positives and ambrotypes, Science and Media Museum
• International Chemical Safety Card 0355: Diethyl ether, IPCS / WHO-ILO
• Cadmium bromide, NOAA CAMEO Chemicals
• Supplying explosives precursors and poison substances: list of chemicals, Home Office (GOV.UK)
• Silver nitrate substance information, ECHA
• ECHA CHEM substance record: Cadmium bromide, European Chemicals Agency (via the Silverlog chemicals database)