I want to make some cheap and easy fixer for film testing with ingredients I have on hand using the formula below. I have Sod. Thiosulfate & Sod. Sulphite. I believe vinegar is basically 5% acetic acid so if I use 5x the amount (250ml) would that work? Can I use Boric Acid powder instead of crystals? I don't need hardening so can I eliminate the Alum?
Water (140F) 600 ml
Sod. Thiosulfate 240 g
Sod. Sulphite 15 g
Acetic Acid (28%) 48 ml
Boric Acid (crystal) 7.5 g
Pot. Alum 15 g
Water to make 1.0 L
Only if you have to harden your film you need all that stuff in there. If you use 200-300 g/l Sodium Thiosulfate crystalline and 10-20 g/l Sodium Sulfite you should be fine, this formula works slowly but ok and lasts forever (shelf life). Sodium Thiosulfate crystalline alone works, too, but working solution shelf life is measured in hours.
With films like delta and tmax any sodium thiosuklate fixer will be unacceptably slow in my book. Fixer isn't exactly expensive; it's the one thing I really never bothered to mix (apart from early experiments with wet plate and alt processes, but I use c41 fixer for those purposes these days).