Calba's Grain Maximizing Monobath

Monobath formula for maximum grain

Part A
Water (45C)700ml
Sodium Sulfite (anhydrous)50g
Sodium Hydroxide10g
Potassium Bromide2g
Part B
Water (25C)300ml
Chrome Alum (optional)20g
Sodium Thiosulfate 70g
Mixing Instructions: Add chemicals in specified sequence. Always use cold water when mixing potassium or sodium hydroxide due to risk of heat reaction. In this case reduce the original amount of hot water to 600ml and add the Sodium Hydroxide to 100ml of cold water prior to adding to Part A.
Dilution: Mix both solutions together to make 1000ml just before use.
Usage: Starting point dev time: 5-7 mins (86F/30C)


This is a monobath formula so no fixing is required. Chrome Alum is not required with modern emulsions. As with any monobath formula results can vary greatly depending on film type and there is a risk of fog/staining so you are advised to run a test roll before processing any important negatives.