Yep, that would probably be better. That was just an idea I had for "develop by inspection" adjustment, and would require an experienced eye, like any DBI process.
Eeek! That sounded like a bunch of digital stuff! For shame!
Eeek! That sounded like a bunch of digital stuff! For shame!
I'd much rather shoot a bracketed test roll of my chosen film (Foma R100, say), cut it in bracket groups after first dev (which I'll be able to see a negative image, so can cut accurately) and then bracket the reducing bath. Might have to do a couple rolls to get the first dev fully dialed in, though, since I keep hearing that standard negative development isn't right (speed issues, contrast issues, etc.) -- never mind that the Tri-X I've done this with got the same first dev I'd have given for negatives.
Might have to do a couple rolls to get the first dev fully dialed in, though, since I keep hearing that standard negative development isn't right (speed issues, contrast issues, etc.)
I always used permanganate bleach and it always worked fine. The bleach I use is made with deionised water andGiven that Foma, Kodak and Ilford all recommend essentially the same acidified permanganate bleach bath, but with widely varying times of immersion (1 min Kodak to 5 mins from Ilford), there is clearly scope for some refinement.
Copper sulfate is used with sodium chloride and not with sodium bisulfate.Wish PE or Jerry Koch were still here to chime in, but I've stayed away from mixing hydrogen peroxide and acetic acid due to the possibility of forming paracetic acid. Several of us have used citric acid and hydrogen peroxide for paper reversal, and I think it's been used for film as well. There's a long thread about it somewhere here at photrio. I've been meaning to try the copper bleach, but with sodium bisulfate.... got as far as purchasing the copper sulfate...
permanganate bleach
Great ,,The bisulfate is used as a reserve of sulfate++ ions, sometimes as a complete substitute for the sulfuric acid, and sometimes just so you don't need to use as much acid. In sulfate bleaches (including permanganate and dichromate versions), it's been my understanding that the developed silver is converted to soluble silver sulfate, with the permanganate or dichromate (powerful oxidizers) acting as catalyst and the sulfuric acid supplying sulfate. If you start with copper sulfate, you have sulfate already in the solution, so the bleach still works without adding sulfate -- but it'll have much more capacity if there's a sulfate reserve in the solution.
What do you suggest to make this bleach solution can live long (in your view)?Shelf life is, once mixed, of no more than two weeks. If a doubt, better making the bleaching lights open, so we can see if it works, also we see the bleach strength from the clearing time, so we can bleach the right time. I learned that after ruining some fllm...
Right, sorry I was not very clear. I meant Copper sulfate, sodium chloride, and a little sodium bisulfate instead of sulfuric acid.Copper sulfate is used with sodium chloride and not with sodium bisulfate
Yes, yes, it is now clear.Right, sorry I was not very clear. I meant Copper sulfate, sodium chloride, and a little sodium bisulfate instead of sulfuric acid.
Does this mean that we can use copper sulfate and only without sodium chloride and without sulfuric acid? (At least in theory)?
Copper bleach formula for C41 (Agfa).The question I'd have is whether there's enough sulfate present if you don't add any. I don't know the purpose of the sodium chloride in a bleach you'd use for B&W reversal; you surely don't want to rehalogenate the developed silver as you'd do in C-41 or E-6 to allow fixing it away. I've have to experiment with copper sulfate without added acid or sodium bisulfate to be sure, but intuitively I would expect some bleaching action, but very low capacity -- you'd need a lot of copper sulfate to do the job.
I don't know the purpose of the sodium chloride in a bleach you'd use for B&W reversal;
When sodium chloride is used with copper sulphate, the bleach acts as a rehalogenating bleach. In B&W reversal processing, this bleach converts the negative silver image into silver chloride. If the bleach step is followed by a rinse in dilute ammonia solution, all the silver chloride is removed while the silver bromide is left intact for subsequent steps of reversal processing.
Yes, brother ,,Wow. That's a good example of going around your ear to get to your elbow. The copper bleach just above your post, for an old C-41 process, is what I'd expect for a rehalogenating bleach, though it's unclear why you'd use copper sulfate in that context rather than potassium ferricyanide. You don't need the acidity (in fact, need to avoid it), get rehalogenated silver and are ready for the fixer. Maybe it's a matter of working faster; I don't know.
Wow. That's a good example of going around your ear to get to your elbow.
better making the bleaching lights open, so we can see if it works
What do you suggest to make this bleach solution can live long (in your view)?
with the exception of Adox CMS 20 ii. It's best to bleach this film in the dark in my experience.
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