Alkaline formalin hardener for films and plates, for use after development. Recommended for the treatment of negatives when the emulsion would otherwise be softened considerably by chemical treatments as in the removal of several types of stains, intensification or reduction.

Dissolve chemicals in order.
Formaldehyde (40% solution)10
Sodium carbonate anhydrous5grams
Water to make1liter

After hardening for 3 minutes, negatives should always be rinsed and immersed for 5 minutes in a fresh acid fixing bath and well washed before further treatment.