Rudi, this is precisely what I am thinking, you have managed to express my understanding of the function of fix bath 1 and bath 2 very well.
Originally Posted by Rudeofus
Doremus, I think you understand some of my goals, indeed, I would like to know if a good, potent sodium sulfite wash aid can function as fix 2—but definitely not as fix 1, which we know, it cannot do. Because the functions of the two baths are quite different, my hypothesis is that it might be able to. However, I do not wish to exceed fix 1 capacity beyond—this is important!—2g/l, which is about 40 sheets of 8x10 per 1 l, which is the same as capacity of a normal fix 1, before you would rotate it out based on Kodak and Ilford recommendations. However, the best part is, based on the Ilford and Digital Truth references, which I quoted above, that capacity of fix 1 is exactly what they are recommending for archival/optimum process when a wash-aid is used. The two approaches seem to have identical capacities.
Originally Posted by Doremus Scudder
In other words: classical 2 bath fixing gives you 4x capacity of fix 1 compared to a single bath. Single bath fixing using alkaline or neutral fxer, with a wash aid, gives you 4x capacity of fix 1 compared to a single bath. So what is the saving? Twofold: you would do the wash aid anyway, so one step can be eliminated. Secondly, in 2 bath fixing, every four rotations you must throw away the 2nd fix, instead of promoting it to 1, due to the carry-over buildup of iodide and other pollutants, according to Kodak. So, if this works (and that is what I am trying to get to grips with) then this is a very considerable saving to the environment, not to mention our time. Also, avoiding a 2nd fix, means even less thiosulfate in the paper fibres etc, as we cut the contact time to a half.
Gerald, thank you for your patient explanations, which I think I follow now. Just to see if I understood you, may I ask you how can we be sure that the slowest reaction is, indeed, that of removal of thiosulfate from paper base, if the duration of the immersion of paper in the fixer can be cut significantly, such as when using Ilford approach of film-strength ammonium thio fixer for 1 minute, or an alkaline/neutral rapid fixer, 12% (film strength) that references say washes out much more easily than the sodium thio? Secondly, am I right to think that you assume that one must use another fixer bath to speed up the removal of thio and silver-thio compounds? If a hypothetical compound X could remove those, would it not be better to rely on that, as there would be no additional thiosulfate entering fibres while desorbing the complexes?
Originally Posted by Gerald C Koch
Thank you, everyone, for humouring me with your explanations and your patience, which I am very grateful for.