Since OP's is a substitute of a substitute, I think it makes little sense to tinker with it further especially since OP is getting results that he likes.
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Is there a place here for some Photoflow in the A bath to improve penetration? If so, it may be possible to reduce the concentration of the active agents in that bath. I am thinking of thin emulsions that don't carry as much from A to B bath.
I think it has more to do with how densely packed the emulsion layers are - and the consequent availability of surface area for reaction in a non solvent and non-active (ie not alkaline enough to start developing the film - emulsion swell peaks around pH 8-9 from recall) bath 'A' - there's a whole heap of emulsion swell agents that effectively act as development accelerators - polyglycols would be a good place to start, but there are quite a few others. Poorly hardened emulsions would be the main risk factor for undesired side-effects
Just curious. How do you know for sure that the first bath developer has not successfully penetrated into all regions of the film in the 3-5 minutes of the bath? Is there any scientific study that you can point me to? Thanks in advance.
I spent quite a bit of time on it and I can assure you that the effort is indeed quite a bit more. Getting something that develops a roll nicely is not hard. Getting the carryover situation to be right is much harder. I made several pretty good developers, but still could only re-use the 2nd bath about 3 times for my best effort. Diafine, by contrast, can use it over and over and get the same results. I documented my best effort here (ironically it was also the first experiment): https://imager.ie/a-phenidone-hydroquinone-two-bath-developer/ This is not intended to be a Diafine replacement, though, it's aimed at higher sharpness (which it achieves).
Karl is right. OP should be worried about carryover accumulation in Part B. And due to his reformulation that uses much higher amounts of developing agents in the first bath, pretty soon the second bath is likely to become a potent developer in itself.
AFAICT from a *lot* of experimenting, the theory that it's the developer absorbed into the film that does all the work is not true. It definitely is part of it, but it's also the amount carried over on the surface of the film and the tank that does as much as anything. And, unless there is a bit of development in the first bath, you just get thin negatives.
Hmmm.. I've done two bath developing using Pyrocat HD concentrate (water based) as the first bath and a single use Carbonate-Bicarbonate buffer with a bit of Sulphite as the second bath. There's no development in the first bath as Pyrocat HD concentrate is acidic. But I never got thin negatives. Neither baths were longer than 5 minutes IIRC.
Phenidone develops in acidic conditions down to like 6.2 if I recall. Try it out some time and I'd be willing to bet the A bath develops a thin image unless it's below that pH.
With a one shot B you don't have to worry about guaranteeing development in A because you can have enough developing agents to do it all in B. If you are concerned about carryover, you have to do some dev in A.
Well I've checked the film after first bath in the Pyrocat HD based process I described earlier.
There was no development which is not surprising because Pyrocat HD concentrate has much lower pH than the minimum required by Phenidone.
Well I've checked the film after first bath in the Pyrocat HD based process I described earlier.
Good to know. You still have a good bit of developing agents as I said and with a one shot B, you don't have carryover to worry about.
Yes, I find single use second bath less of a headache. And in the particular case of Pyrocat HD, my second bath was not expensive at all as it was based on Carbonate-Bicarbonate buffer spiked with a bit of Sulphite.
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Do you have a recommendation for divided Pyrocat HD? It seems to vary:
https://www.photrio.com/forum/threads/divided-pyrocat-hd.51000/
Original divided Pyrocat HD, as recommended by Sandy, used either 1:10 or 1:20 dilution for the first bath and Carbonate based second bath IIRC. It is meant primarily for very high contrast scenes needing significant highlight compression. I took a slightly different approach where I used stock Pyrocat HD in the first bath and a lower pH second bath as the stock is highly concentrated. I customized the second bath for specific films but you might want to start with this: 4g Sodium carbonate + 2g Sodium bicarbonate + 6g Sodium sulphite in 600ml water. Both baths were for 5 minutes duration at 25C. Agitation for the first bath was continuous for the first minute and three inversions every minute thereafter. Agitation for the second bath was 3 gentle inversions at the start followed by one gentle inversion every minute thereafter. Second bath is one shot. If you are going to try it, please feel free to increase/decrease pH of the second bath based on the results of your initial test as some tuning is needed for every film.
I think Diafine has pretty solid & high capacity (an important, yet overlooked factor in many home-designed formulae) carbonate/ bicarbonate buffering in part B - which the pH I recall people have found would seem to support. Raising your buffer capacity significantly (and going to carbonate/ bicarbonate) might be worthwhile.
From recall, I found Diafine had a fairly noticeable seasoning effect too - and I do wonder if that had something to do with there being sufficient carryover to essentially turn bath B into a somewhat effective developer in and of itself, with bath A effectively providing enough ongoing replenishment & pre-charging the system for bath B to do most of the work - or it may simply have been build-up of byproducts in bath A - in other words, I'm open minded about how much development is or isn't happening in bath A, but I think Bath B's role is often dismissed rather too freely. The problem is that to thoroughly resolve this would require a rather large R&D effort, possibly extending to microdensitometry and the like.
And that's before considering the problems of what compensation actually delivers (XP2 Super in C-41's curve exhibits real compensation behaviour via the DIR couplers etc - as opposed to the lowered average gradient that is often mistakenly referred to as 'compensation') - and Dimezone S/ HQ ratios can be manipulated to raise edge sharpness, but this is likely challenging without microdensitometry or similar (unless it causes 'coverage' problems that become grossly visible as strong granularity) to balance edge sharpness and good development.
There's nothing unique about Diafine with regards to capacity. All commonly used two bath developers have good capacity including Thornton's Two Bath (T2B).
According to user reports, very little or no development happens in the first bath of Diafine. So it is unlikely that there is any substantial bromide buildup in the first bath that demands increased activity of the second bath. In contrast, substantial development does take place in the first bath of T2B and a bromide buildup is likely after a few rolls have been passed through the first bath.
Time spent in the second bath is small - 3 to 5 minutes. It's unlikely that a "seasoned" second bath of Diafine can fully develop film in such a short duration of time even with reduced induction time unless the second bath itself is a powerful developer. It should be easy to test this.
According to user reports, very little or no development happens in the first bath of Diafine. So it is unlikely that there is any substantial bromide buildup in the first bath that demands increased activity of the second bath. In contrast, substantial development does take place in the first bath of T2B and a bromide buildup is likely after a few rolls have been passed through the first bath.
Time spent in the second bath is small - 3 to 5 minutes. It's unlikely that a "seasoned" second bath of Diafine can fully develop film in such a short duration of time even with reduced induction time unless the second bath itself is a powerful developer. It should be easy to test this.
B bath usually is announced as borax or metaborate plus sulfite...
I developed ortho Tri-X and xray film in Diafine. Both showed an image when removed from bath A. It was low-density and low-contrast.
Ok, Diafine formula itself might have gone through changes over time. Way back in 2003 Lex Jenkins reported that there was no development in the first bath. See this discussion.
The Diafine I was using was made long before that.
Anyway, not being able to see it doesn't mean there's no developing activity. There's bound to be some. If I'd taken those sheets and fixed them instead of putting them in bath B, they would have ended up transparent.
Not sure I understood. Did you mean there could be development of silver halide that doesn't add anything to the density?
All I mean is that the image developed onto the sheets in bath A alone was very faint (but still visible) and may have disappeared completely if fixed. It also stands to reason that, in the process of going from dry film to fully developed, there is a point where some development has occurred that would not be visible. There is development before visible development, or you'd never get to visible development. That's all I mean.
Could the faint silver be sequestered by the BTA in the first bath as if it were fog?
Diafine carried a warning about not using an acid stop, which is usually a giveaway for it containing carbonate (not a problem with anything other than poorly hardened films - and it tells you how old the formula is).
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