I want to know :
What is the advantage of this bleach and not available with a copper bleacher?
I want to know :I don't know it, this has been a drawback of the permanganate bleach since many decades ago, so if no chemist found a solution...
Possibly a cold storage may help to conserve it, as in general chemical reactions are cinetics slowed with lower a temperature.
I always used permanganate bleach and it always worked fine. The bleach I use is made with deionised water and
1g/l Potassium permanganate
50g/l Sodium bisulfate
It's good to dissolve permanganate in half the amount of water needed and let it rest there, while giving it the occasional stir. It dissolves rather slowly and it's too dark to figure out if it has completely dissolved, so filtering the permanganate solution is a very good idea.
Before committing any films to processing that I haven't tried before, I do the first three steps of the process in full light, in q graduate. I develop a piece of film in FD, then rinse, bleach and clear. The film seems to be fully bleached in a minute or so, at 20°C. Regardless of this, I bleach for 5' and I haven't had a single case of emulsion sliding off the base, or become too soft to touch. That said, I don't remove the film from the reel and expose to light on typical Jobo and Paterson reels. Another poster said something about light fogging being uneven, but if you keep the film immersed in a bowl of water, then it will give perfectly even fogging, no marks whatsoever. I don't use any fancy high wattage lights, just a 70W tungsten bulb at a distance of 20-30cm for a couple of minutes from each side of the reel. I also spin the reel in the water while exposing to light.
It is a very special fim, what surpirsed me is this statement in the datasheet:
"After the development you MUST use an acidic stop bath before fixing. Do NOT use plain water."
They do not say why, but perhaps the reason has a link with what you say.
I have a strong feeling that I am more foolish than usual.@Lachlan Young Thanks for the link/PDFs. There was this very interesting post few years ago about a long life permanganate bleach, with 20g/l of "Calgon-Photo", which is sodium hexametaphosphate. The patent bleach has 20g/l sodium potassium hexametaphosphate. I've been meaning to try this, but always forget it. Perhaps I should get serious and mix a 500ml test batch.
About what? Can you be more specific?I have a strong feeling that I am more foolish than usual.
My foolishness and dementia increased. I do not know what to do ?
When I learn something new, I feel like I was a fool.About what? Can you be more specific?
When it is being used as CMS 20 you do not want it to carry on developing to completion (and its very high surface area relative to the developer will ensure it'll keep going faster than you might think), but to arrest the process in a matter of seconds. An acid stop is designed to do this.
I want to know :
What is the advantage of this bleach and not available with a copper bleacher?
I partially agree with you,Probably the copper bleacher is the best technically. I did all sorts of experiments with permanganate and dichromate to bleach CMS 20 with no good results, but the copper bleach works with CMS 20, removing metallic silver without damaging the silver halide, as Raghu teached me.
With regular pictorial film copper bleacher may have an slight plus as it may conserve better highlight detail as it is able to not disolve the smallest halide crystals, like those in CMS 20.
In fact dichromate is reportedly better for that than permanganate. But the challenging job is with CMS 20, with such small crystals bleaching has to be very selective to not damage the silver halides.
I partially agree with you,
But you have not tested anhydrous copper sulfate.
It can do the job with precision and go into the smallest details.
Unfortunately, many colleagues do not mention anything about the significant differences between these two copies of copper sulfate,
Anhydrous is very expensive, and its results are very excellent,
I used it in a negative color and its results were great, but the problem is that it needs pre-bleach and a cleansing solution after bleach. (This is the problem, you need three steps instead of one step)
I used it in a negative color and its results were great, but the problem is that it needs pre-bleach and a cleansing solution after bleach. (This is the problem, you need three steps instead of one step)
Thank you, my dear brother.To be clear, at no point was I criticizing others who used differential solubility to remove a rehalogenated image and leave undeveloped halide in place -- it just seems like rehalogenating and then an additional bath in ammonium hydroxide solution is more work than directly dissolving the developed silver and I don't see copper sulfate as a huge improvement over potassium permanganate. What I'd use for B&W reversal? At present, probably acidified peroxide. Nothing particularly hazardous in storage (even 9% isn't any more hazardous than stop bath concentrate). I've used dichromate bleach in the past, it works very well but I prefer something less aggressively anti-biology if I have the choice. @mohmad khatab you can almost certainly get 3% peroxide locally, and may be able to get 9% or 12%.
@Lachlan Young Thanks for the link/PDFs. There was this very interesting post few years ago about a long life permanganate bleach, with 20g/l of "Calgon-Photo", which is sodium hexametaphosphate. The patent bleach has 20g/l sodium potassium hexametaphosphate. I've been meaning to try this, but always forget it. Perhaps I should get serious and mix a 500ml test batch.
There is no need to arrest development instantly... if water bath takes a bit more time to stop development then we can slightly shorten development time, may be there is another reason.
It may be something about fixing....
I do not buy cheap copper sulphate recycled from copper waste.@mohmad khatab I understand you've gotten better results with anhydrous copper sulfate than with the hydrated crystalline form -- but if both are of equal purity this should make no difference, other than requiring you compensate the weight of crystals relative to the weight of anhydrous to account for the included water of hydration (just as I do when I use 20 Mule Team laundry borax -- the decahydrate -- in place of anhydrous sodium tetraborate in a developer). What I presume has happened in your case, then, is that the anhydrous copper sulfate you have is of better purity than the crystalline product you can obtain, or just possibly the crystals contain some specific impurities that inhibit the bleaching action or otherwise cause trouble in the process.
other than requiring you compensate the weight of crystals relative to the weight of anhydrous to account for the included water of hydration (just as I do when I use 20 Mule Team laundry borax -- the decahydrate -- in place of anhydrous sodium tetraborate in a developer)
Surprisingly, it was found that only the addition of polyglycols as development accelerators resulted in a considerably improved complete development of the shadow region after first development, and thus resulted in an improvement in the clarity of the light regions after reversal development. Apart from this advantage, however, it proved to be a disadvantage when using polyglycols that almost all the polyglycols, when used in the requisite amounts, resulted in significantly reduced maximum densities after reversal development. As shown in examples 6 to 12, compared with polyethylene glycols P1000, P1500, P4000 and P12000 the use of polyethylene glycols P200 and P400 resulted in the lowest loss of maximum density, so that P200 and P400 appeared to be the most suitable for this developer. All further investigations were therefore performed using P400 as the development accelerator."
The PEG 1500 compound is used as a development accelerator, which helps clear the highlights.
Doubtful - it's more likely for the same reason you need an effective stop bath when lith printing - to arrest the infectious development before it crashes every value above a certain level of exposure to pure black. CMS 20 has more in common with a litho emulsion than a pictorial emulsion. There may also be an oxidation product formed from a water stop that causes problems (likely fogging) that would not be the case with an acid stop.
The PEG 1500 compound is used as a development accelerator, which helps clear the highlights. This comes from the patent text, page 3, after the "55" marker:
The DR5 guy is the master nº 1 in this business, he reverses magistrally any kind of BW film (with CMS 20 exception, I guess his bleaching is not compatible, copper required, the other exception is was Neopan), I feel that his success is from optimally managing the Silver Reserve, and finely enhancing both thinning any fog and boosting DMax from the right infectious development and from a wise toning.
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