maybe this is called hicheking the threas, but: Can I use a working solution for more than one film? just yesterday I developed 3 rolls in Jobo tanks (a one-tank and a two-tank) prepared 500ml of working solution, did it with the one-tank. 250ml of course, then i just filled it back to the non used 250ml and used those 500ml for the remaining two-tank. Then i discarded the hypo. I once heard that this is single shot only, but then again I have never encountered any problems.
I always do the mixing like this: get myself a bucket, or bowl, with the desired markings. (I think it is 3 and 3.8 litres).
1) pour in the water at the temperature it shows, to the first marking
2) Fully dissolve the powder
3) Fill it with water to the second marking
4) stir and then fill into some bottles, label them. There you go.
5)working solution is prepared easily. 1 part hypo (1+0 - stock) and 4 parts water.
Btw: how important is the temperature of the water to mix the stock solution? There is an exact number of degrees. (21C I think). I'm always pretty exact but it annoys me a bit to temperature 3L. Will +/- a few degrees also work?