Caffenol and Vit.C based developers and fixer

I started a thread at Flickr, where I defended to use the fixer (Ammonium Thiosulfate) very diluted and just once. I thought, if 100ml fixer is to be diluted in 500ml water and will fix about 10 films, then each film uses 10ml of fixer. So, if this 10ml are putted in one 500ml bath, we have a dilution of 1:50. I tried first with 1:60 dilution and this took 1 hour to fix a film. With this dilution I could identify some white spots in the pictures (this problem has been identified also by other experimenters).

Caffenol Strong + 1:60 fixer

Next time I raised the dilution to 1:30 and, accidentally, I did not wash very well between developer and fixer. I got images like this:

Caffenol Strong + 1:30 fixer, bad wash in between

I came to the hypothesis that maybe the developer and fixer had some incompatibility. The developer was my Caffenol Strong with coffee and Vitamine C.

So, I did another experiment, keeping the dilution and film and washing very well between developer and fixer.

Caffenol Strong + 1:30 dilution and a 15min. wash in between

Please don't look to the right side of the picture, it is not sharp as it should. This new camera I made needs some adjustments. But here are again the small white points like in the first picture with 1:60, I mean 1:30,  dilution of the fixer.

Analizing with an enlarging lens the film, I could see that these points were a kind of grains that could be cleaned out with a soft cloth, giving then:

The same as above + cleaning with soft cloth

Note: I made a mistake, I meant 1:30 (see in red above) instead of 1:60.

Observations: For the films I used until now, Fomapan 100 and Ilford FP4, a 1:30 solution of the liquid concentrated fixer (Fomafix) needs one hour to fix, i.e., half an hour to clear.