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Possibly Alan
Those filaments can touch but I think joining together to form a contigous lump would be rare, I think Ron was right when he suggested that what we are seeing is a visual effect though the stacked layers, rather than grains joining. I think the later is less likely with the new hardened emulsions.
Mark Antony
Last edited by Mark Antony; 12-14-2010 at 08:47 AM.
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Ian
I'm not sure what would cause the effect you witnessed, the conversation I had with a Kodak engineer here in Cambridge UK was that his personal tests of Tmax (which he worked on in the 80's) that process teperature would not cause reticulaion. I pressed him about their recomendation of 25°c as the temp for machines with TMax RT and would lower wash temps cause problems (our processor used mains water) and he stated that differences in temp between solutions wasn't a problem.
Not all machines control the wash, ours had a Pro Co 7kw (like a shower) heater in line the wash would vary (±5°c) at different times of the year-I never saw a difference in grain or any noticable reticualtion.
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Can we define what we are talking about?
The first post by PE mentions "Grain Clumping" but what is that? What are we talking about. If it does not exist, now can it have a name? Where did the name come from (popular culture or the chemistry literature?).
If it does exist, then can we define it. How can we discuss something without a definition?
What is grain anyway, clumps of silver (right or no?). So, are we are discussing clumps clumping?
No opinion one way or the other, I'm just reading the thread for entertainment at the moment.
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Mark the effects are reticulation caused by rapid swelling/shrinking of the gelatin, but not usually so so severe as to be typical classic reticulation, it's been called micro reticulation or grain clumping by some.
In the 60's the older emulsions would all exhibit reticulation with poor temperature controls, but by the time films like FP4 etc were launched film hardening was more effective.
Most modern films may well be fine with a +/- 5° C variation at the wash stage but some aren't. Also it's not so simple as it's a combination of high pH or pH change, choice of developer and then temperature variations that seems to give the biggest problems.
It's a pity no-one has a copy of the 1980's article that was in Darkroom techniques on Micro Reticulation (excessive grain clumping) as the issues were fully tested and shown to exist.
Ian
Last edited by Ian Grant; 12-14-2010 at 09:15 AM.
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[QUOTE=ic-racer;1105794]Can we define what we are talking about?/QUOTE]
"Grain Clumping"
Excessive grain, often caused bt a mild form of reticulation. I'd add unexpected excessive grain.
Ian
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Ian I get your point, but I'm not sure that grain clumping= micro reticulation. One certainly exists (although rare in moden emulsions) and is a physical development/emulsion fault. The other is an observation of an effect though the body of an emulsion derived from optics-in other words its in the observer rather than the emulsion.
Reticulation is an emulsion fault and independant of grain, graininess is perceptual though the stack rather than a physical movement of grains though the emulsion.
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 Originally Posted by Mark Antony
Ian I get your point, but I'm not sure that grain clumping= micro reticulation. One certainly exists (although rare in moden emulsions) and is a physical development/emulsion fault. The other is an observation of an effect though the body of an emulsion derived from optics-in other words its in the observer rather than the emulsion.
Reticulation is an emulsion fault and independant of grain, graininess is perceptual though the stack rather than a physical movement of grains though the emulsion.
It's well known that classic reticulation causes grain clumping, it's lesser form micro reticulation also causes grain clumping. Micro reticulation manifests itself as excessive grain - grain clumping.
Yes classic reticulation is a gelatin layer fault, micro reticulation occurs before that stage is reached but is also caused by swell & contraction of the gelatin.
The terms were coined many years ago.
There can be other reasons for excessive grain clumping, in appropriate developer choice although the grain in films like Tmax & Delta is more a product of the emulsion and is less dependent on the developer used. This is what Alan was talking about.
So not all grain clumping is micro reticulation, but all micro reticulation is seen as a form of grain clumping.
Ian
Last edited by Ian Grant; 12-14-2010 at 10:29 AM.
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Originally Posted by Ian Grant
It's well known that classic reticulation causes grain clumping, it's lesser form micro reticulation also causes grain clumping. Micro reticulation manifests itself as excessive grain - grain clumping.
Ian
All well and good Ian, but can you quote a source?
I think that Mark Antony has said it well in his several posts.
Alan, these experiments I quote were done from low to high pH. In fact, the astronomers preferred the high pH to get high contrast.
The references you cite are correct, and Haist, Chapter 6 Volume I gives detailed electron micrographs of developing grains showing morphology changes as a function of development type such as physical vs chemical development. He also shows photos of development which causes filaments from one grain to overlap filaments from another grain, but he does not show any 3D separation as does the work of Ross.
As pH goes up, contrast goes up and the number of centers goes up. Viewed from above, down through the coating, the appearance is that there are clumps. This is dispelled when one views from the side. You see a cone of exposed and developed silver which varies in amount of developed silver as a function of pH or temperature.
I have processed films at 120 deg F with no sign of reticulation.
As a final note, I have an e-mail which confirms the fact that the Kostinsky effect has been "proven" and "disproven" over the nearly 100 years since it was "discovered". So, the data on it is equivocal. And, to date, I have seen no data on the movement of Silver metal or Silver Halide crystals in gelatin unless you force reticulation and in that case, the entire image will move. There is no atomic scale force inducing merger that has been shown in the literature AFAIK. I have never seen clumps form.
PE
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Guys;
My OP comes from the early days of astonomical photography in which astronomers were concerned about three things:
1. Image movement (placing stars at the wrong location)
2. Image movement (placing spectral lines at the wrong wavelength)
3. Formation of clumps by image movement which would give the appearance of a false star.
This article disproved all of the items in up to 16 developers, at two temperatures and with and without hardener in the process. With careful examination, they ruled out any significant movement of the developed silver image.
I know that there are some strong opinions, but this evidence is rather compelling to me.
As pH and / or temperature go up, the developed silver image will change morphology and the image structure will look different to the human eye, but there has been no movement or merger ever shown.
PE
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I think that micro reticulation and grain clumping are very different, here is an image of a cubic type grain which has by development changed into a filamentary growth.
I think (perceived) grain clumping is a stochastic formation of grains through the emulsion. Different developers give different formations of crystalline growth some filamentary some not, and differing tonality and perceived graininess as a result.
Rather than the actual grains migrating though the gelatine to form physical 'clumps'
Mark Antony
Last edited by Mark Antony; 12-14-2010 at 11:10 AM.
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