Reducer for very hard negatives such as over-developed and over-exposed ones.

The same as G503, this reducer attacks the highlights first but it has more predictable results.

Mix chemicals in order.
Ammonium persulphate
Sulphuric acid2.5mililiters
Water to make

Use distilled water if available and add 1.5 mililiters of a 1% of common salt per 100 mililiters of water. This reducer does not keep and must be made up immediately before use.

Remove the negative from the reducer before the desired degree of reduction has been achieved and immerse the negative in a plain Sodium thiosulphate bath for 5 minutes then wash thoroughly.