I was looking for a formula that would use up some of my ageing stock of sodium thiosufate and thought I’d try this one from the Darkroom Cookbook (Formula #124). The combination with ammonium chloride results in a faster fixing action. I also find it fairly odourless.
- Water at 52°C‡ – 750ml
- Sodium Thiosulfate – 200g
- Ammonium Chloride – 50g
- Potassium Metabisulfite† – 10g
- Water to make 1 litre
‡Hypo (sodium thiosulfate) is endothermic, which means that it absorbs heat as it dissolves, hence the warm starting temperature.
†The metabisulfite is to acidify the fixer; I reduced the amount from that stated, using half, as I use this fixer with films processed in PMK where an acid fix can sometimes affect the desired negative staining.