Fogging - Relationship between filmbase thickness and fogging?

[Theodor Bader]

Hello!

The list of factors that can cause or promote fogging in black and white film is very, very long.

Is there perhaps another connection between the thickness/thinness of the film base, or the material itself, and fogging?

So far, I haven't been able to find anything about it, neither in books nor online.

Perhaps this is just a mirage from the darkroom?

What do you know about this?

 

[MattKing]

What sort of fogging are you referring to?
Chemical fogging, age fog, fogging due to cosmic radiation, light fog or???
The material used and thickness of it is certainly relevant to the anti-halation characteristics of the film.
And halation would likely make light fog worse.

 

[FredK]

The film's base is supposed to be totally inert so that fogging of any such does not occur. That said, any impurities within the gel-sub layer applied to the base for emulsion adhesion could lead to long-term fogging issues. The suppliers of the materials used for gel-sub must test for trace components and report their results to manufacturers for each production batch they make. Specifications are very tight to ensure fogging does not occur.

Within the materials going into the emulsions and overcoat layers it is the very same for chemical suppliers. Specifications are very tight and batch information is shared and reviewed before being used. Any batches with question could be / would be tested using very small-scale making and coating equipment and samples would receive accelerated storage conditioning and testing to see if fog is formed. Only if fog was below levels would those constituents be used.

I can't speak for other suppliers but Kodak does a lot of testing on any material components used in the make-up of sales units (inks, plastics, labels, adhesives, tapes, etc.) to ensure that those components will not affect the film's performance expectations.

Silver halide grains, and their fogging propensity, is tied to their size more than anything and fogging from gamma radiation over time. I use, as an example, in a 2 meter square placing coffee cans all through the square and throwing a dollar worth of pennies up into the air to let them distribute onto/into the cans. Then, remove the can counting the pennies in each and replacing the cans in the square with quarters and doing the same throwing another 1 dollar in pennies. How many quarters will hold the same number of pennies as the coffee cans? This is how gamma radiation fogs the larger grains which absorb more of the gamma radiation vs. the tiny grains (the quarters) which gather the same number within the square, but each grain a much lower level (number) which will not develop up into fog in processing.

 

[Bill Burk]

And of course many film bases are tinted for anti-halation. Many people mistake the intentional (approximately 0.20) density as fog.

 

[Theodor Bader]

What sort of fogging are you referring to?
Chemical fogging, age fog, fogging due to cosmic radiation, light fog or???
The material used and thickness of it is certainly relevant to the anti-halation characteristics of the film.
And halation would likely make light fog worse.

Unfortunately, I have no idea where the fogging is coming from.

The producer assured me he did everything in his power to prevent fogging.

The batch test came back positive.

Besides the higher ASA rating (400), the only other thing I noticed was the extreme thinness of the film.

According to the producer, all layers are 0.06mm thick. That makes it quite difficult to load a 120 film into the developing tank's spiral.

Fortunately, I also have the Paterson system, which uses small balls as transport aids. That works.

 

[Theodor Bader]

The film's base is supposed to be totally inert so that fogging of any such does not occur. That said, any impurities within the gel-sub layer applied to the base for emulsion adhesion could lead to long-term fogging issues. The suppliers of the materials used for gel-sub must test for trace components and report their results to manufacturers for each production batch they make. Specifications are very tight to ensure fogging does not occur.

Within the materials going into the emulsions and overcoat layers it is the very same for chemical suppliers. Specifications are very tight and batch information is shared and reviewed before being used. Any batches with question could be / would be tested using very small-scale making and coating equipment and samples would receive accelerated storage conditioning and testing to see if fog is formed. Only if fog was below levels would those constituents be used.

I can't speak for other suppliers but Kodak does a lot of testing on any material components used in the make-up of sales units (inks, plastics, labels, adhesives, tapes, etc.) to ensure that those components will not affect the film's performance expectations.

Silver halide grains, and their fogging propensity, is tied to their size more than anything and fogging from gamma radiation over time. I use, as an example, in a 2 meter square placing coffee cans all through the square and throwing a dollar worth of pennies up into the air to let them distribute onto/into the cans. Then, remove the can counting the pennies in each and replacing the cans in the square with quarters and doing the same throwing another 1 dollar in pennies. How many quarters will hold the same number of pennies as the coffee cans? This is how gamma radiation fogs the larger grains which absorb more of the gamma radiation vs. the tiny grains (the quarters) which gather the same number within the square, but each grain a much lower level (number) which will not develop up into fog in processing.

Wow, I'm truly impressed by everything you do to maintain standards and ensure quality.

Since the batch was released to the market after testing positive, as the manufacturer assured me, the fogging is most likely caused by the customer, specifically me. None of the other films from the same shipment showed even the slightest hint of fogging; only this one film did.

I've already been offered a refund for the 120 film. That's completely out of the question until I've ruled out every conceivable cause. You could accuse me of being stubborn, but I couldn't care less.

 

[xkaes]

Have you measured -- in some way -- the density (light loss) in the film when unexposed and completely fixed? If all you have is an eyeball, you could compare it to a known, low-fog film.

 

[Theodor Bader]

And of course many film bases are tinted for anti-halation. Many people mistake the intentional (approximately 0.20) density as fog.

I don't think I belong to the group you're referring to.

In my roughly 45-year career developing black and white films (as a hobby photographer, of course, since the late 1970s), I've developed all kinds of films myself, with all the variations that are natural over such a long period. It has always worked very well!

Fogging was extremely rarely an issue at all.

I certainly won't give up until I get good results. (A real stickler.)

 

[Bill Burk]

I mean me. Whenever I develop 35mm film and 120 in a session, as I start to take readings, I am often startled by the fog in 35mm. 120 film base is usually clear and typically 0.05 density. It’s the 35mm that’s gray. I often look up on the datasheets to verify what the gray tint is supposed to be, but the density is not always documented.

Since your tests are revealing speeds close to nominal, in practical printing results, I don't know that you are seeing significant fog, because the first thing that would do is defeat shadow detail and force you to choose a lower speed rating for the film.

How bad is the fog you're seeing? Is it mottled (paper backing defect) or even overall. Have you subtracted the base (fixed a piece of the film without developing to find base density)?

 

[Theodor Bader]

I mean me. Whenever I develop 35mm film and 120 in a session, as I start to take readings, I am often startled by the fog in 35mm. 120 film base is usually clear and typically 0.05 density. It’s the 35mm that’s gray. I often look up on the datasheets to verify what the gray tint is supposed to be, but the density is not always documented.

Since your tests are revealing speeds close to nominal, in practical printing results, I don't know that you are seeing significant fog, because the first thing that would do is defeat shadow detail and force you to choose a lower speed rating for the film.

How bad is the fog you're seeing? Is it mottled (paper backing defect) or even overall. Have you subtracted the base (fixed a piece of the film without developing to find base density)?

Hi Bill,

First, I need to clarify that the film I'm "struggling" with is NOT the one I described with test photos here: https://www.photrio.com/forum/threads/bulk-rolling-120-220-film.217810/post-2996089

It's the 400 ASA version on a thinner base that's giving me trouble.


My experience is completely consistent with yours, namely that fogging is more of an issue, if it occurs at all, with 35mm films.

Over the years, I've seen all sorts of non-fogging, but colored, film bases. However, they've all been in very thin and unobtrusive pastel shades. These colors are partly due to the developer.

As mentioned, I've been using Caffenol and similar alternative developers for over 10 years. Oddly enough, the black tea developer tints the film base greenish (NOT brownish, as one would expect).

I developed the 100 ASA version with Caffenol C-L (long-development version). It's 120 film, and it's crystal clear.

I was absolutely thrilled!

However, I'll still perform your base fog test on both.

The 400 ASA version is incredibly dense.

At the moment, all sorts of factors are still suspect: backing paper, light leakage in the darkroom, sudden shutter speed error, developer.

I don't want to publish the results I've seen with the 400 ASA version here.

It's important for me to mention that I've also tested the 35mm versions, FN64, and Foto-200. Both are flawless! The very best for me is the 100 ASA version in 4x5" format.

My hope is that this sheet film will continue to be available for ever.

I didn't proclaim the resurrection of Agfapan 100 in the aforementioned post without reason !

 

[Bill Burk]

Forgot about the pink dye on Kodak TMY2 sheet film. That washes out, I can see it because I use white porcelain trays and wash by hand, takes about six changes of water until it comes out clear.

 

[Theodor Bader]

Forgot about the pink dye on Kodak TMY2 sheet film. That washes out, I can see it because I use white porcelain trays and wash by hand, takes about six changes of water until it comes out clear.

Yes I remember the pink/reddish color of TMY.

I have subtracted the base , fixed a piece of the film without developing.



As good as no density (minimal light bluish ).
After washing 20 ninutes this color is reduced to "nothing"....

Means this that :

I need to look elsewhere for the reason for the fogging/light leak or what ever it is.....?