Grain clumping, a controversial issue

[Photo Engineer]

I have been struck by the many comments here and elsewhere about grain clumping. I have been searching my library and other resources on this topic, and find no authoritative sources that say it takes place but several that say it does not, and they offer proof.

The closest I can come to a literature reference is this paraphrase, which I believe is from one of the works by Ross, to be cited below. Basically, he contends that some people claim to have seen clumps when viewing a film but what they are really seeing are the inevitable statistical patterns we see when we look at thousands upon thousands of grains stacked vertically. When we look at a cross section, they are separated into distinct grains. The first photo below is an example of looking down through a black dot on a film. You can see an indistinct edge made up of what appear to be clumps. Well, I'll get into that later on here.

F. E. Ross, a scientist working at Kodak in the 20s was tasked to find out several things that related to astrophotography. Basically, the astronomers wanted to know if silver metal particles could move horizontally in film as they had observed some movement due to the Kostinsy effect in spectrograms.

Kostinsky effect

The development effect in which dense image points are inclined to move apart, relative to each other, and light image points to move together, relative to each other. This occurs because developer is not being equally distributed over the image point and is rapidly exhausted when to heavily exposed image points are close together.

http://www.swpp.co.uk/glossary/kostinsky_effect.htm

http://books.google.com/books?id=WX...kQ6AEwAQ#v=onepage&q=kostinsky effect&f=false

Ross has written several papers and books on the subject of the movement of silver metal images and particles in gelatin and shows that silver metal just does not move very far. He has studied tanning developers and ordinary developers over a pH range that would satisfy most of us and he did his work on glass plates to insure that the dimensional stability of films of that era was not interfering.

This was summarized in the book above and in his article "Film distortion and accuracy of photographic registration of position." I've attached photos below.

Photo #1, looking down at a small circular exposure showing what appear to be clumps around the edges (see comments above)

Photo #2, cross section of the same exposure using a tanning developer and showing the tanning effect in lower gelatin layer thickness.

Photo #3, cross section of the same exposure using a non-tanning developer. The gelatin has expanded in this case.

Photo #4, cross section showing two identical exposures processed in a tanning developer

Using this type of measurement, Ross was able to show that the images or parts thereof moved less than 2 microns from the original site of exposure. There was no evidence of clumping.

In Photo #5, I have produced an aggregated emulsion by using a low level of gelatin. Now, you may call this clumping as well. You can do this in 2 ways. You use too little gelatin for conditions when you make an emulsion or you use too little gelatin when coating an emulsion. Either way, grains coalesce and "clump" or "aggregate" and you get pepper grain. You see, when a grain touches another grain before or during development and forms a larger "lump", you get fog which is what you see in this print. This is how clumping appears in a print. White dots are seen. They can be virtually any size from the equivalent of several grains up to thousands of grains of Silver Halide.

I would like to thank those who helped me in off-line exchanges on this topic. In particular, I would like to thank AgX for his mention of Kostinsky. And for his permission to use this from our off-line discussion. In the articles I have, Ross does not mention Kostinsky.

PE

 

[Hexavalent]

Thanks for that post Ron. The x-sections do tell the tale.

 

[Alan Johnson]

It is well known, and anyone can try it for themselves,that as developer pH is increased the size of the observed grain increases.This is attributed to swelling of the emulsion and grain clumping.
If you deny grain clumping you need another explanation for the increase of observed grain size with pH. So what is your alternative explanation?

 

[Ian Grant]

This is isn't really related to grain clumping/micro reticulation caused by temperature variations during processing which we know exists but varies significantly depending on the particular emulsions used, and also the pH of the developer which is also unrelated to tanning effects.

Grain clumping is independent of pH & temperature (as long as tightly controlled) and more a combination of factors, emulsion type, developer formulae, and temperature variations. The very fact that it does occur and particularly with Tmax 400 & Neopan 400 means as Alan says there's a need for quite a different explanation.

My own gut instinct is that the hardening of many emulsions has lead people to be complacent about temperature controls, when I began film developing in the early60's films were very much softer, with far less hardening and you had to keep tight temperature control or you got full blown reticulation. Modern film hardening controls this meaning greater tolerance to changes, but with some developer/film combinations the hardening becomes weakened. Developers with a high pH containing Hydroxide seem to be an issue, but Hydroxide is known to soften Gelatin etc.

So we have a current situation where many films are quite robust but a handful aren't, processing has to be tight enough to be safe to prevent micro reticulation/grain clumping with films like Tmax 400, Neopan 400 etc.

Ian

 

[Mark Antony]

Count me in as another doubter of ' physical grain clumping' in all the journals I've read state that the grains don't move together but rather the shape and how the grain grows gives the visual effect of clumping.

Grains start out as crystaline shapes and with certain developers can form into what Mees called a 'spongy amorphorous mass' looked at though a microscope this looks like wire wool.
It is these types of grain viewed though the several layers that give the impression of 'clumping'.

Mark
PS My understanding of the Kostinsky effect is that as fine detail increases in frequency it's density falls.

 

[Ian Grant]

Count me in as another doubter of ' physical grain clumping' in all the journals I've read state that the grains don't move together but rather the shape and how the grain grows gives the visual effect of clumping.

Grains start out as crystaline shapes and with certain developers can form into what Mees called a 'spongy amorphorous mass' looked at though a microscope this looks like wire wool.
It is these types of grain viewed though the several layers that give the impression of 'clumping'.

Mark
PS My understanding of the Kostinsky effect is that as fine detail increases in frequency it's density falls.

Then how do you explain how films of the same type, processed in the same developer, stop bath and fixer and washed with the same water can vary from one set being fine grained as expected and the other having such excessive grain that they were unusable.

The films were Tmax 400, the developer Xtol replenished, Acetic stop bath and Hypam fixer.

The ONLY variable was attention to the temperature of all stages of the process, the films I processed 35mm Tmax 400 (fine grained) the rolls of 120 Tmax 400 were processed by another photographer using my chemistry. I did notice he didn't take a temperature reading for the wash water, it was a cold spell at the time in the UK.

Grain clumping/Micro reticulation exists but Kodak's research assumes stable and repeatable processing temperatures, all research requires tight tolerances so none of the published research shows it

Plenty of others have seen the same problems most just don't realise the cause, poor process control.

Ian

 

[Mark Antony]

I'd imagine that in that case the grain rather than physically clumping by moving in the body of the emulsionis is due to one or more differing perameters changing grain shape.
Both James and Vanneslow noted this effect, it can happen with too much agitation or too higher temperature, but the grains aren't moving though the emulsion they're physically changing shape (although when they change they can touch other grains).
The filaments grow because of the difference in charge at the tips of the filamentry structures.

I think that Kodak has tested (I know this because I've spoken to Kodak engineers) T max films at a variety of temperatures, one engineer told me candidly that the Gelatin in Tmax films was so hardened that reticulation was almost impossible and that the team couldn't get it to happen at 50°C+ the idea of grains physically clumping though a body of an emulsion is unlikely due to temperature.
If you have observed that, it would not be in accordance with Kodaks testing or my personal experience.
Regards
Mark Antony

 

[Alan Johnson]

LFA Mason, Photographic Processing Chemistry p120 notes:
"Graininess is also often worse at high pH values, due partly to the rapid development of the coarse grains and partly to the greater spread of the silver filaments into the much softer gelatin"
Jacobson & Jacobson,Developing p53 note:
"As the development proceeds,it is seen that the reduced silver in the two adjacent grains bridges the gap between the and so forms one large irregular grain..."
Maybe for brevity these processes may be lumped together and called grain clumping,this appears quite consistent with the view that it is not caused by the movement of the grains through the emulsion, it is a matter of the definition of "grain clumping" perhaps.

 

[Ian Grant]

It's not temperature itself Mark, all manufacturers test films at a variety of temperatures it's excessive variations and is only now seen with a handful of emulsions.

I process Neopan - Acros 100 & 400, at 26-27° C with no problems, no increase in grain (same with Tmax 400 when I used it) however others have posted of excessive grain with Tmax 400 & Neopan 400 and even full blown reticulation and the emulsion frilling off the base with the Neopan.

The question of why seems to be purely down to variations in control of process temperatures. It falls outside Kodak/Fuji etc testing at various process temperatures because these test were done for machine processing where temperature control is typically +/- 0.2°C

Ian

 

[Mark Antony]

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

 

[Mark Antony]

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.

 

[ic-racer]

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.

 

[Ian Grant]

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

 

[Ian Grant]

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

 

[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.

 

[Ian Grant]

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

 

[Photo Engineer]

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

 

[Photo Engineer]

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

 

[Mark Antony]

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

 

[Ian Grant]

I've quoted sources in the past Ron, I'm not going to post the same information again.

The facts are that excessive temperature shocks cause micro reticulation with a small number of films and Ron (PE) himself prefers to call the excessive grain "grain clumping" in previous threads. Again as he knows other APUG members have attested to having excessive grain when they've used Tmax & Neopan 400 when they were lax with temperature controls.

Ian

 

[Ian Grant]

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

This article doesn't relate to reticulation caused by excessive temperature changes. At the time it was written all emulsions reticulated easily but I'd guess all photographers had seen reticulation first hand and books then stressed good temperature controls.

Ian

 

[Bruce Watson]

...from one of the works by Ross, to be cited below. Basically, he contends that some people claim to have seen clumps when viewing a film but what they are really seeing are the inevitable statistical patterns we see when we look at thousands upon thousands of grains stacked vertically. When we look at a cross section, they are separated into distinct grains.

This is what I always thought of as grain clumping. It's that film is a 3D medium -- the emulsion has depth. When you look through it, you look through all of it. In a heavily exposed area you might see thousands of grains, all stacked one above the other. But they aren't all the same size, or same shape. So they "overlap" and form a non-transparent grouping of grains that's bigger than any of the individual grains. Thus -- a "grain clump".

Density is formed by metallic silver grains, yes? More density means more grains. And more grains means more overlapping, which in turn means "grain clumps" which are "bigger". This accounts for the grainy highlights from most B&W negative films. Said another way, this accounts for the spread in the sizes of the visible grains -- resulting in a range of sizes -- which is why grain size is sometimes referenced as an RMS average size (whatever meaning this might have).

This was my interpretation, though I can't remember ever having seen it written down anywhere. How wrong am I?

 

[Photo Engineer]

This is what I always thought of as grain clumping. It's that film is a 3D medium -- the emulsion has depth. When you look through it, you look through all of it. In a heavily exposed area you might see thousands of grains, all stacked one above the other. But they aren't all the same size, or same shape. So they "overlap" and form a non-transparent grouping of grains that's bigger than any of the individual grains. Thus -- a "grain clump".

Density is formed by metallic silver grains, yes? More density means more grains. And more grains means more overlapping, which in turn means "grain clumps" which are "bigger". This accounts for the grainy highlights from most B&W negative films. Said another way, this accounts for the spread in the sizes of the visible grains -- resulting in a range of sizes -- which is why grain size is sometimes referenced as an RMS average size (whatever meaning this might have).

This was my interpretation, though I can't remember ever having seen it written down anywhere. How wrong am I?

Bruce;

You have it correct! In fact, you lead into the next phase of this.

RMS = Root Mean Square and is usually said RMSG where G = Granularity.

Grain varies with type of development (high solvent, low solvent) and other factors such as pH as I mentioned above. Haist shows micrographs of several types of grain. I have yet to see an authoritative post on grain clumping or micro reticulation.

So, here is a plot of Grain vs Density. Note how grain varies with development time! This is how our eye fools us into thinking something has happened and the explanation is not correct. Grain even varies with development time at equivalent density.

It was mandatory to study the image structure on every coating I made. This included photo micrographs and electron micrographs, RMSG, etc.. I coated 10 coatings every other week, so in one year that was about 250 variants on a given film product. I've processed from 68F to 120F as well during these studies. I believe that the Ross paper expresses the true situation.

I have seen no definitive or authoritative references to the contrary. This is particularly true when as you say, and as Mark Antony says, it is a 3D effect. You need cross sections to prove the point.

PE

 

[Jerevan]

Okay, so what the disagreement revolves around is "apparent grain clumping" vs "actual physical grain clumping"? As far as boiling the film in hot developer - that is one thing, but what happens to the gelatine structure when temperature goes haywire? Does the silver still stay where it is?

If Ross made this experiment in the 1920s - does it still hold value? Does the active versus inactive gelatine have any impact on the issue?

 

[ic-racer]

Ok but now we have "Grain" "Granulairity" and "Grainyness" and "root mean squared granularity" in that last post. We probably need specific definitons of those and how they are measured to continue.

Can we agree in the discussion that "Grain Clumping" means the net movement of silver in the emulsion in a "grain-centric" direction, independent of any stocastic movement.

We need to agree on what constitutes movement also.

If a "grain" were to gain silver mass on one side and lose silver mass on the opposide side, the grain's center of mass has moved but the molecules in the grain have not moved.