As I restarted, a few years ago, doing film photography, I was surprised with many other alternatives to the classic developer agents, namely coffee, tee, Vit. C and so on. And I wondered why were people not looking for alternative fixers too. So, after some investigation, I stated, as early as 2012, following: read the post.
This subject has been discussed to completion at Flickr in the Caffenol Group that I abandoned due to some trolls there.
Some days ago, one of the best Caffenol researchers, Reinhold G. owner of the blog Caffenol, sent me a link of a forum were Salt as fixer has been mentioned again. It seems that after that huge discussion at Flickr to convince people that Salt really works as fixer, nothing else happened but now, after 3 years, somebody is trying it again. In fact, Reinhold didn't believe it too as first, but after a while he also admited here that Salt really works as fixer.
Not only salt (Sodium Chloride), but other Chlorides will do it and who knows other chemicals too. Ammonium Hydroxide (Ammonia) is also a fixer like I said in that mentioned post.
Salt, aka Sodium Chloride, was used as fixer before Mr. Herschell proposed Sodium Thiosulfate, that worked much better. Later on, Ammonium Thiosulfate proved to be faster than Sodium Thiosulfate, known among photographers as Sodium Hyposulfite or just Hypo.
Yesterday I tried another possibility that showed to be better than salt and even better than Ammonia, it worked in only a dozen of minutes but may be still better, I think, if used more concentrated. Knowing that Sodium Thiosulfate may be produced by heating a Sulfite solution with elemental Sulfur, I supposed that a similar reaction using Potassium Metabisulfite and Sulfur would take place and Potassium Thiosulfate could result.
So, I dissolved 25g Metabisulfite in 500 ml water in a heat resistant glass beaker and added a tea spoon of Sulfur and stired. I tried this solution as fixer and didn't work. I heated the solution for 1 hour in moderate hot fire, until I had only 250 ml solution. I let it cool and tried it as fixer. It cleared a piece of film TMax (one of the more difficults to fix) in some 30 minutes, so, in one hour it would be totally fixed.
PS - A more precise recipe can be: 8 g Sulfur and 56 g Potassium Metabisulfite in 700 ml solution. Let it boil until you have only 350 ml solution. Filter (some Sulfur will still not react) and use it as fixer. Fixing time is about 1 hour for TMax 400.