Versatile Tanning and Stopping Bath
A tanning bath for damaged or “delicate” emulsions—and as a standard replacement for a regular stop bath.
About the foot bath
This bath is primarily intended for photographic materials with damaged, “delicate,” or weakened emulsions, but it can be used as a standard stop bath with any films or papers. Thanks to its tanning effect, subsequent solutions can be used at temperatures up to 25 °C, the drying time is reduced by a factor of 2–3, and damage to or melting of the photographic paper’s emulsion during hot glossing is virtually eliminated. It is not recommended to place materials in this bath without an intermediate rinse if development was performed in a strongly alkaline developer—alkali entering the acidic tanning bath may cause localized precipitation.
How to Prepare and Use
- 1Process the photographic material immediately after the developer for 0.5–2 minutes to stop development and perform a light tanning.
- 2For a stronger tanning effect, increase the treatment time to 5–7 minutes. The standard operating temperature of the solution is 20 °C.
Pros
- Allows for further processing at elevated temperatures (up to 25 °C)
- Reduces the material's drying time by a factor of 2–3
- Protects damaged and weakened emulsions
- The prepared solution can be stored for up to 1 year
Cons
- Doubling makes subsequent rinsing more difficult and may slow down the removal of the fixer
- Not suitable for materials that do not require intermediate rinsing after a strongly alkaline developer
- A partially used solution lasts only about 3 weeks
Recipe for 1 liter
Chemical structures: PubChem (public domain)
Mixing it at home
A stop bath with a hardening action; made from two solutions — the alum, and boric acid with metabisulfite.
- 1Dissolve potassium aluminum alum (20 g) in 400–450 mL of distilled water at a temperature of 25–30 °C, stirring constantly until completely dissolved.
- 2In a separate container, using the same amount of water at the same temperature, dissolve boric acid (8 g) and potassium metabisulfite (10 g)—the contents of the second packet.
- 3Wait until both solutions have completely dissolved and cooled to room temperature (20–25 °C).
- 4Combine the two solutions and add distilled water to bring the total volume to 1 liter. Filter if necessary.
Key points
- It stops development in 0.5–2 minutes and hardens (toughens) the gelatin at the same time; hold it for 5–7 minutes for strong hardening.