It's not polyethylene glycol that is used to mix Pyrocat HD part A, but propylene glycol. The only reason for using it is to make a very long lasting solution.
It's not polyethylene glycol that is used to mix Pyrocat HD part A, but propylene glycol. The only reason for using it is to make a very long lasting solution.Interestingly, Polyethylene Glycol is used by some in Pyrocat developers. I wonder if that made any difference to the activity of Pyrocat developers. Or is it only HQMS that benefits by the use of PEG?
It's not polyethylene glycol that is used to mix Pyrocat HD part A, but propylene glycol. The only reason for using it is to make a very long lasting solution.
I mix my Pyrocat-HD "A" solution in polyethylene glycol (PEG) and leave the KBr and sodium metabisulfite out. I just assumed these two components would be difficult to dissolve in PEG. BTW, the pyrocatechcol and phenidone dissolve in the PEG at temperatures between 140F and 160F.
That's very strange and it's the only time I've seen using polyethylene glycol to make Pyrocat HD part A. Propylene glycol is what is suggested.See post #10 in this thread: https://www.photrio.com/forum/threads/mixing-pyrocat-hd-from-scratch.5517/
Well, follow up on what Agfa and Kodak's mid-90's processes were. Note the correlations and why. Kodak's cine reversal bleach bath is essentially the same as the one recommended in the Agfa patent upthread - aka a chelation agent added to acidified permanganate. If two different research teams of considerable ability came to the same conclusion for processes intended for industrial use, follow what they did. Note that in both first developers intended for still use - ie the Kodak TMax kit & the Agfa Scala process, both first developers seem to use no extra solvency, but instead use PEG as an accelerator - and possibly some degree of in-situ HQMS formation. D-94A using DTOD is slightly different, it's meant for roller transport use & a 90s developing time - rather different from the ~6 mins aim in Scala - D-94A is also significantly more alkaline than the aim for the first developer in the Agfa patent. The Scala process dates from about 1995, superseding whatever process the ISO 32 Dia-Direct used. It seems likely that there was a discovery that higher solvency developers can have sharpness benefits in BW negative (and colour positive films), but that an development accelerator was more effective in getting full speed, clean highlights and excellent Dmax in BW transparencies. So in other words, your research should start from here: no solvency in either developer; use a polyglycol as a development accelerator; both developers need to be strong and super-additive, with the first developer potentially aiming to form or use HQMS - and as high definition as possible; chemical reversal ignored until both developers perform consistently; bleach bath as per Kodak and Agfa recommendations; ignore the 'cookbooks' and what 'worked' with old relatively uncontrolled emulsions of 70 years ago.
Interestingly, Polyethylene Glycol is used by some in Pyrocat developers. I wonder if that made any difference to the activity of Pyrocat developers. Or is it only HQMS that benefits by the use of PEG?
Pyrocat in glycol does not contain PEG polymer ( https://en.wikipedia.org/wiki/Polyethylene_glycol)
See post #3 in this thread: https://www.photrio.com/forum/threads/glycol-tea-and-glycerine.3680/
, in that post #3 a member speaks about PEG, but you won't find a single Pyrocat formulation with it: HD, HDC, M, MC, P, PC... no one uses PEG,
Pyrocat is preferred by many current workers over pyrogagallol (pyrogallic acid) for several reasons.
...
8. if mixed in polyethylene glycol, which it should be, it lasts for an extreme length of time. I have never had any go bad.
See post #203 above where I quoted Tom Hoskinson on using PEG for part A of Pyrocat HD. Also see post #3 in https://www.photrio.com/forum/threads/why-pyrocat.102378/:
See post #203 above where I quoted Tom Hoskinson on using PEG for part A of Pyrocat HD. Also see post #3 in https://www.photrio.com/forum/threads/why-pyrocat.102378/:
It's interesting to note that Formulary sells PEG and the product description says this:
"Polyethylene glycol is non-toxic and is used in a variety of products including as a component in some developer formulas".
And what's the role played by PEG in them?
And what's the role played by PEG in them?
What are these developer formulas? And what's the role played by PEG in them?
I'don't know if a clear benefit may be obtained from PEG, the fact that in 16 years that substitution has not been popular at all suggests there is no clear advantage, but...
It's likely dependent on the molecular weight of PEG used - a low weight one may have little effect - but I always take the view these sort of developers attract followers whose actual process control abilities lag far behind what they think they are. You have to remember that there's a lot more opinion than science in most commentary on Pyrocat.
It's likely dependent on the molecular weight of PEG used - a low weight one may have little effect - but I always take the view these sort of developers attract followers whose actual process control abilities lag far behind what they think they are. You have to remember that there's a lot more opinion than science in most commentary on Pyrocat.
I'don't know if a clear benefit may be obtained from PEG, the fact that in 16 years that substitution has not been popular at all suggests there is no clear advantage,
Staining developers may deliver a fine grain, as the silver developent is lower for the same density... but also Xtol delivers a fine grain with lots of acutance.
My view is that very linear films like TMX may deliver dificult to (optically) print highlights, as density may easily skyrocket. Certainly Pyro stain blocks more the blue in the highlights than in the low densities because stain color, so with VC paper highlights are printed with an effective lower contrast grade, helping its depiction. IMO the stain solves that shoulder lack "pitfall".
The AGFA-Gaevert patent mentions that the use of PEG also resulted in fog which reduced DMax. They had to use 5-methylbenzotriazole as antifoggant to deal with the fog and apparently other antifoggants didn't work well. In summary, use of PEG as development accelerator is not straightforward. It's a complex game involving a specific developing agent and a specific antifoggant.
Of course using the shoulder and toe of the film requires an accurate metering and mastering the particular film/processing. For complex scenes, the more we nail the tonal manipulation in the negative the less manipulation work we have in the printing, but any pitfall will have an impact. Instead with a linear film we have a more flexible negative, YMMV, I guess.
But regarding reversal processing, we don't have much that post opportunity. We can always bracket, but shooting slides is more challenging because we should nail the job... to me for metering slides we need similar skills than when metering for negative film when wanting to use the toe/shoulder, we need accuracy and preferably using spot metering.
the bleach with 20g/l sodium hexametaphosphate came out exactly as it was, which I believe is a good sign.
Yes, I've kept this bleach and I'll let you know how well it keeps.Would be good to know how long this version of permanganate bleach will keep well - hours, days, or weeks.
That's because HexMePh inhibits the formation of MnO2 deposits, the brown-red color you saw with your previous version of the bleach.On the subject of permanganate bleach, I made an observation last night. I mixed the following bleach formula in deionised water:
20g sodium hexametaphosphate
1g potassium permanganate
50g sodium bisulfate
Top up to 1000ml
My previous formula was the same, except the omission of sodium hexametaphosphate and seems to bleach fully developed film leaders in a minute or so. My previous bleach would come out of the tank with a slightly different colour. Instead of the dark purple of permanganate, it would take a more reddish, perhaps slightly brown colour. This time, the bleach with 20g/l sodium hexametaphosphate came out exactly as it was, which I believe is a good sign.
This was Mr. Ruddy 's view too.On the subject of permanganate bleach, I made an observation last night. I mixed the following bleach formula in deionised water:
20g sodium hexametaphosphate
1g potassium permanganate
50g sodium bisulfate
Top up to 1000ml
My previous formula was the same, except the omission of sodium hexametaphosphate and seems to bleach fully developed film leaders in a minute or so. My previous bleach would come out of the tank with a slightly different colour. Instead of the dark purple of permanganate, it would take a more reddish, perhaps slightly brown colour. This time, the bleach with 20g/l sodium hexametaphosphate came out exactly as it was, which I believe is a good sign.
I added sodium bisulfate, not sulfate. This is a substitute for sulfuric acid and works fine. Instead of using H2SO4, I used NaHSO4. This might also reduce emulsion softening from permanganate a bit, but I can't be sure about it, I haven't made any side by side tests.This was Mr. Ruddy 's view too.
You added sodium sulfate and this was not the original formula. This is in order to try to tame this solution and control its aggressiveness,
- But you permanently deleted sulfur sorrel. Why?
You could add sulfuric acid as the original formula states, and at the same time add 100 grams sodium sulfate, two grams permanganate and the rest of the formula as the original formula states.
Deleting sulfuric acid will benefit one side and may harm another side.
- You should hold the stick in the middle, my dear colleague.
They will do that.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?