Direct effect(s) of alkalinity on granularity
This was originally a PM to PE but I figured I'd make it a thread in case anyone is interested.
This concerns the DIRECT influence (if any) of pH on granularity.
We often read that when it comes to fine grain development, pH is an important factor. More specifically, the contention is that in the context of fine grain development it is important to have relatively mild alkalinity. The indirect reason for this is well established – ie all other things being equal, lower alkalinity means a longer development time and therefore more time for the sulfite to etch away at the crystals.
But then there are those supposed direct effects of higher alkalinity. Everything from gelatin softening to “clumping”. One of the problems is “clumping” as a descriptor for an effect (increased non-homogeneity of developed silver for a given density) is used by different people to describe the overall effect of a few different causes/mechanisms. Some of them may be valid, some may not.
For example, to most people “clumping” in the context of high alkalinity means the actual grains clump together as development progresses, presumably further facilitated by the softening of the gelatin. This is sometimes referred to as "grain migration". Zawadzki addressed this in one of the Myths columns she used to co-author with Dickerson in Photo Techniques. To quote her: “Doesn’t happen”. However, Haist may have had a different view: “Developing solutions for producing fine-grained images should reduce the silver from each grain in place in the gelatin layer. To achieve this aim, the solution must be relatively low in alkalinity. Highly alkaline solutions cause the gelatin of the emulsion layer to swell and soften more than solutions at lower pH.”
How about another cause for the clumping effect, one having to do with the actual formation of the metallic silver filaments themselves. Suppose there is no actual “grain migration” at higher solution alkalinities. In that case, what difference would pH per se make when it comes to non-homogeneity of developed silver (ie increased granularity)? In the same paragraph Haist goes on to say “High alkalinity also causes a more rapid and vigorous formation of silver filaments. Both the softened gelatin and the vigorous formation of the silver particles increase the possibility that the silver filaments will be larger and more nonuniform in distribution.”
So, I’m still unclear on whether or not alkalinity (within reason and barring extremes) directly affects granularity. Perhaps gelatin swelling can indeed cause some sort of deformation even if the grains themselves don’t move within the gelatin. On the other hand, current Kodak and Ilford films are well hardened.
Here is PE's initial response:
Originally Posted by Photo Engineer
I figured I'd add some thoughts on a possible experiment. Suppose we took solvent effects out of the equation (because it would be extremely complicated to formulate the experimental developers if they were solvent in nature). In other words, as little sulfite (or any other compounds which might promote solvency) as possible.
A suitable "control" developer might be the Beutler formula (Metol, a small amount of sulfite, carbonate alkali). Crawley's FX-1 might also do. Then suppose we ran an experiment in which the formula was adjusted to replace the carbonate with a small amount of say borax, or even sodium bicarbonate perhaps. Ideally what we'd have (albeit with a much longer development time) is a developer that (hopefully?) (possibly?) duplicated the sensitometric characteristics of the control developer with a given film, still with minimal/no solvent effects, but at a significantly lower pH.
Suppose that could be done. What differences might we see (if any), in graininess?
Of course as PE reminds us, you can't have everything, and there might by other image structure tradeoffs (sharpness for example). But keep in mind this thought experiment is strictly from the perspective of granularity/graininess in relation to pH.
Last edited by Michael R 1974; 04-15-2014 at 12:01 PM. Click to view previous post history.
This might be of interest. The exploration certainly couldn't start more simply. There is also more info on the previous and following pages.
Last edited by dwross; 04-15-2014 at 11:42 AM. Click to view previous post history.
It's a wide open topic because there are developers like Rodinal with a high pH which give excellent fine grain and there's also developers with almost neutral pH which are very fine grain, it''s dependant on the overal developer formulae and the developing agent(s) used.
Rodinal was one of the developers that I had in mind, but there are so many work alike developers I hesitated to get into specifics on that topic.
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I'm probably the least scientific minded person you could ever meet in terms of training and education, but I'm pretty good at observing and noting results. I know for a fact that my D76 used to get more active (higher PH) over time, and the grain got out of hand at some point. It was giving me fits with increased contrast and grain compared to the first negs I developed in it. Switching to TD-16 solved that issue. Before doing that I chased a number of false phantoms like switching to glass bottles, using saran wrap on the tops, glass marbles, etc. Now I just store the developer in those plastic brown bottles from Freestyle. Development is absolutely consistent over at least a 3 month time span now, whereas w/ the D76, 3-4 weeks was all I could get.
That may not answer your question per se, but to me it means that w/ this particular developer, an increase in PH equals an increase in contrast and grain. Of course Kodak saw the same thing decades ago and is supposed to have fixed the problem w/ their new formulations, yet for me, their new, improved D76 exhibited all the same problems of the old D76. Fortunately, the new stuff retains all of the same excellent developing characteristics as the old, just not for very long, at least in my house.
Last edited by momus; 04-15-2014 at 01:19 PM. Click to view previous post history.
We have to make sure it's "apples to apples" for a variety of variables. We know that the degree of development directly affects granularity, so it would be important in any comparison to make sure a careful sensitometric analysis is done first, particularly contrast.
Within a B&W context, part of the problem is we can't really find commercial products which are comparable. High pH developers are also typically formulated as "acutance" formulas, with properties besides pH per se which don't promote fine grain. And fine grain developers are typically formulated not only to work at a relatively low/mild pH, but they also contain a lot of sulfite. Too many variables there.
I'm not entirely convinced the developing agent per se is a significant direct determinant of granularity. I can't find any evidence of this (with the obvious exception of PPD which on its own promotes solvency). Furthermore at the microscopic scale, it becomes even more counterintuitive in some cases. With agents such as Metol and Phenidone, which are active at low alkalinity, the formation of metallic silver is apparently relatively "violent", with the original geometric structure/shape of the grain being more or less obliterrated, while Hydroquinone (a compound requiring much higher alkalinity, and one we don't normally associate on its own with "fine grain") apparently allows the shape of the original grain to remain relatively intact.
Rodinal is another interesting example of a high pH, low sulfite developer. Ian - in your view does it truly give fine grain??
One of the reasons for this thread is a "fear" I've always had of high pH developers from the perspective of graininess, and it was troubling me recently in some work I was doing on some experimental formulas. I'm trying to figure out whether or not the fear is well founded. So far the scientists seem to be in conflict (I'll add Troop to this list - all over the FDC the point is made that low alkalinity per se is important for fine grain).
PE - any thoughts on whether or not my proposed experiment has any merit?
Last edited by Michael R 1974; 04-15-2014 at 02:20 PM. Click to view previous post history.
Reason: repeated paragraphs for some reason
I think if you take a specific developer formula (and dilution) and look at the effects of increasing or decreasing the pH ylou can have a valid "Direct effect of Alkalinity on Granularity".
However high alkalinity can have adverse effects on surface artifacts of an emulsion, causing apparent graininess in scans or prints. TMY and Neopan 400 were the most susceptible. This is due to softening of the super-coating.
So Rodinal used carefully can give superb fine grain, with bad temperature control it has a reputation for being very grainy. Many years ago now the late Peter Goldfield who'd worked with Minor White championed the use of Rodinal with modern T grain emulsions APX25 or 10, Tmax 100 & 400, I was highly skeptical until I tried APX100 & Tmax 100 in Rodinal myself. My 35mm negatives with both films in Rodinal are extremely fine grain and very sharp and great tonality.