Ilford IF-13 Potassium Alum Acid Hardener-Fixer
This fixer is intended for use with photographic papers.
STOCK HARDENING SOLUTION
Sodium Sulphite, anhyd . . . 50g
Acetic Acid, glacial . . . 75ml
Potassium Alum, cryst . . . 100g
Add water to make . . . 1 litre
Dissolve the sulphite in 200cc of water warmed to 52C or 125F thoroughly and allow it to cool. Then add the acid very slowly with constant stirring.
Dissolve the alum in 600cc of water warmed to 52C or 125F. Allow it to cool to below 20C (68F).
Pour the alum solution slowly and carefully INTO the acid solution, not the other way around. Top off with water to attain your 1 litre volume.
Dissolve 200g of Sodium thiosulphate (hypo), crystal, into 500cc of warm (52C or 125F) water. Allow to cool and then add 125cc stock hardening solution into it and then top it off with water to attain a volumne of 1 litre.