Grain, Micro reticulation & B&W fim process temperature deviations

[Ray Rogers]

Hi guys!

Well, I just want to say that I think the terms micro-reticulation and especially "grain-clumping", the lack of solid data, and the lack of a sample are at the center of our problem here.

I have some doubt as to if the grain is actually clumping... or growing, but the images I saw were more granular... and "micro-reticulation" sounds like a perfect term...

Don't want to make any promises I can't keep, but I should have some samples around here. If someone wanted to examine them, with the equipment needed to characterize their condition, I could hunt for the little devils. Other than that, someone might reticulate some older(?) film for a cheap and dirty visual comparison...

I don't know if they are the same as what Ian (and others) spoke of but it might be.
Between me and Ian, we should be able to get samples to dismiss or embrace.

It is a possibility anyway.

(Ian - it might simply be what reticulation looks like these days on "modern" films. w/o extream measures being taken)

 

[Kirk Keyes]

Ralph - how did you try to test it?

What about taking a roll of film (or two identical rolls) with stepwedges or even exposures on each frame and taking one roll (or half a roll) and doing a plunge into 0C water at the end of processing/washing? If it doesn't cause outright reticulation, perhaps it will show an increase of grain?

 

[Kirk Keyes]

PE - we all know that silver halide peptizes with gelatin. And we all know that ionic silver can do so as well, as shown by the dark stains on the fingers of wet plate collodion photographers. But does the metallic silver that's being reduced in the film during development peptize with the gelatin? If so, then it will be bound to the gelatin, if not, then it's free to move somewhat free of the motion of the gelatin matrix.

Also, I don't think anyone has mentioned the elastic modulus of silver metal vs gelatin. I suspect that the elasticity of silver metal, even as filaments, is much higher than hardened gelatin.

I assume that expansion due to temperature changes is negligible for the temperature changes that we are discussion, but swell is certainly not. Silver metal will not swell compared to gelatin as it changes pH or even moisture content going from dry film before processing to wet during processing and back to dry again after.

If the silver does not bend to match the movement of the gelatin during swelling, then perhaps it could be pulled into a smaller volume than previous to swelling. The silver resists movement with the swelling gelatin, and the gelatin pulls free from the silver. As the gelatin shrinks back, the silver is caught by the gelatin and pushed into a smaller grain or "clump".

Does mechanical flexing of film cause this issue? I've never heard anyone mention it, but what about repeated flexing of a piece of wet film over a mandril of a small diameter, say 1/2 inch or smaller, to cause "clumping". You wouldn't want something tight enough to cause physical damage to the gelatin, but something that small might induce clumping if the silver is indeed not able to keep up with the motion of the gelatin.

 

[Shawn Dougherty]

Just to be clear about my case in particular...

I would call what I've experienced a "slight increase in grain". I've seen the extreme examples of reticulation in textbooks. That is not what I have found here, by any measure. As stated, simply "a slight increase in grain" on a normally exposed and processed negative where there are no other variables (that I can come up with) and this has been with TMY2 and Rodinal in 120 format. And as I said, seems to be in the winter when my tap water was coldest.

 

[RalphLambrecht]

Ralph - how did you try to test it?

What about taking a roll of film (or two identical rolls) with stepwedges or even exposures on each frame and taking one roll (or half a roll) and doing a plunge into 0C water at the end of processing/washing? If it doesn't cause outright reticulation, perhaps it will show an increase of grain?

That and what Ian described in post #48!

 

[Photo Engineer]

PE - we all know that silver halide peptizes with gelatin. And we all know that ionic silver can do so as well, as shown by the dark stains on the fingers of wet plate collodion photographers. But does the metallic silver that's being reduced in the film during development peptize with the gelatin? If so, then it will be bound to the gelatin, if not, then it's free to move somewhat free of the motion of the gelatin matrix.

Also, I don't think anyone has mentioned the elastic modulus of silver metal vs gelatin. I suspect that the elasticity of silver metal, even as filaments, is much higher than hardened gelatin.

I assume that expansion due to temperature changes is negligible for the temperature changes that we are discussion, but swell is certainly not. Silver metal will not swell compared to gelatin as it changes pH or even moisture content going from dry film before processing to wet during processing and back to dry again after.

If the silver does not bend to match the movement of the gelatin during swelling, then perhaps it could be pulled into a smaller volume than previous to swelling. The silver resists movement with the swelling gelatin, and the gelatin pulls free from the silver. As the gelatin shrinks back, the silver is caught by the gelatin and pushed into a smaller grain or "clump".

Does mechanical flexing of film cause this issue? I've never heard anyone mention it, but what about repeated flexing of a piece of wet film over a mandril of a small diameter, say 1/2 inch or smaller, to cause "clumping". You wouldn't want something tight enough to cause physical damage to the gelatin, but something that small might induce clumping if the silver is indeed not able to keep up with the motion of the gelatin.

Kirk;

All of the above is possible, but the other engineers that I talked to said that it would take a lot of heat energy to cause this type of problem. And, they added that by the time the silver moved, the gelatin would show distinct signs of classic reticulation as well as clumps. This is why it was never a major topic AFAIK. The film would have been ruined by the reticulation before the other effect took place.

OTOH, clumping is known as a coating defect or a making defect directly related to AgX crystal migration or non-random distribution of grains during making or coating and due usually to low gelatin or poor stirring (mixing) at some point during the manufacture.

I'm open minded on this. Ian's remarks and those of others have convinced me to remain open, but the results are rather anecdotal and scanty to say the least. No one has set out to demonstrate it on even two pieces of film, with the same image, but processed differently to stress one of the images.

PE