The myth about film and paper aging

[Photo Engineer]

I have seen a lot of posts here and elsewhere about film aging to make it look good for the consumer or professional or whatever characteristic that the aged film is supposed to gain by keeping.

I have pretty much tried to put that myth to rest, but today I realized that there was a reason behind this which I should post.

Kodak and other companies used, in order of time frame since they began manufacturing photo materials, chrome alum, formladelyde and then formaldehyde + mucochloric acid as hardeners before switching to the current hardeners. Of course, no hardener was used in the very early days.

Chrome alum is noted for needing a long time to reach maximum hardness, and formalin requires a long time to achieve the same degree of hardness, but then can continue to harden. The mixture of hardners hardens more quickly and can use less formalin.

In the case of formalin, it goes through an optimum position and then begins to over harden through an effect called afterhardening. This results in brittle coatings and a change in sensitometry plus a growth of fog. The reaction of formalin with gelatin is slow and incomplete, especially at neutral to acidic pH values as is the case with film. Both Haist and Mees describe all of this in their texts, even though some have disputed these facts in posts here and elsewhere.

The new hardeners are so effective, they allow processes up to 100 F (38 C). They harden instantly right at the moment of coating. Therefore a series of methods are used to slow down hardening. In fact, these newest hardeners are so effective, I have run processes at 120 F.

As a result, films and papers are kept for a short time to allow the coatings to reach optimum hardness before sale. The only product I knew of that was kept to age into being good, was Type "R" paper. All others were good, but merely not hard enough. Type "R" paper had awful sensitometry when freshly coated and had to be kept for 6 months before it became stable and usable. It is one of the few products that changed, then stopped for a long time before it aged too much and finally went bad.

The earliest films were not hardened, and since the melting point of gelatin in water is 68 F, that was the reason behind the original B&W processing temperature. Today, B&W films are the least hardened of them all to allow dense silver images to form, but many modern Kodak films can be processed as high as 100 F.

So, if you hear that a film is aged before release, it is a near certainty that it is due to hardening effects. I have processed coatings right from the end of the coating machine at 100F and they were salable materials in all respects. In fact, that is one of the common characteristics of most good quality photo products. When coated they should be good.

PE

 

[Roger Hicks]

Dear PE,

Was it ever true?

And if not, what was the difference between ER and EPR, apart from the little slip with the actual film speed in with the EPR? We were all told that it was aging for colour balance in the 70s, and I remember the relief when 'professional' films came in and we didn't need to batch-test for speed and colour balance.

One further point, heard from Ilford long ago, was that the reason they got the film speed so wrong with the original Delta 400 (long remedied, of course) was that the film they used for testing was not aged enough. I seem to recall also that Tri-X went over comparatively recently to modern hardeners -- the current version, in fact.

You know far more about this than I, so I do not wish to dispute what you say, merely to find out a bit more historical background.

Cheers,

R.

 

[Photo Engineer]

If a film is hardened with Formalin or the like, it goes through a speed - fog shift with age with an optimum in the middle.

AFAIK, all film products converted from formalin hardening in the 70s or 80s. The only one that might still use it is Kodachrome, as the current formula is so ancient. That is why the rumor might have arisen, in fact.

I remember this due to modifications made to the coating procedures of films during this time period due to the rapid hardening of the new hardener. B&W films did lag behind color due to the problem of having good development (a swell effect) with the high hardness imparted by the new hardener.

Pro films and amateur films differ in color contrast and in some chemical ingredients according to Kodak, but at Fuji, according to their web site, the pro film is just a special cut of the amateur film. It is as they say, a center cut. Kodak even shows the curve shape differences.

For one thing, Kodak pro films are slightly more pushable than amateur films, and this was once shown in a rather lengthy article on Kodak's web site. Amateur films generally have better latent image keeping, as it is expected that the pro treats his film better than the amateur.

Gold film has higher contrast and color saturation due to the flare in cheaper cameras such as the disposable cameras we see becoming so popular, whereas the Portra films have a lower contrast and a range of saturations for the pro. This is achieved by a totally different formulation.

A formalin hardened film, or a film with new hardener at low levels will show either total disintigration or reticulation if placed in 100F water. If it stays together but slides off the support, then the subbing layer is insufficient to handle that temperature, but the emulsion is probably hard enough.

A characteristic of the new hardeners from Kodak, Fuji and Ilford is the difficulty to create reticulation for unusual effects.

PE

 

[Keith Tapscott.]

A characteristic of the new hardeners from Kodak, Fuji and Ilford is the difficulty to create reticulation for unusual effects.

PE

Not a bad thing at all IMHO, as there are many ways of creating "pictorial effects" at the printing stage with out having to beat the film up.

 

[PatTrent]

Interesting. Thanks, PhotoEngineer for providing that insight.

The next time I process B&W on a hot summer day and the air conditioning is acting up, I won't worry so much.

 

[Photo Engineer]

Let me add something here to make a further point.

When we designed Kodacolor Gold 400 film, we (the team of 3) had a set of aim curves that we had to match. It included the sensitometric (characteristic) curve, RMS Granularity and Sharpness (resolution). When we met those goals we sent the product formula and curves to the pilot plant to duplicate the product. When they did, they sent it to the plant and the plant duplicated it and then it went on sale.

Now, if we had to wait 2 - 6 months to get that aim every time we coated a test in research or development, it would take forever to produce a product.

No, we coated to the aim, and then processed the day or the day after we coated the product when using the new hardener. When using formalin we processed about a week later and expected to see just about the final result. Our coating schedule allowed us a coating set of 10 coatings every other week, so we had roughly 7 - 8 days of testing and 1 day of writing up our new experiments. The 10th day was the next coating day and so on. Each weeks experiments from day 1 - 8 had to be the basis for the next set on day 10. And, this inlcuded the fact that every coating went in for raw stock keeping tests, latent image and etc... So every week, on the last day, we took a break from this rigid schedule and tested the keeping effects of prior coatings going back as much as a year. This was in order to prove THAT THERE WAS NO CHANGE! This is the key issue here.

Doing R&D with a fugitive or moving target so to speak is like groping in the dark. We would get nowhere. So, in all of my practical product development experience which includes Ektacolor paper, Kodacolor Gold 400, Ektaflex R and C, PR10 and several other unreleased products, we never had a moving target to plan around. We never planned on the product having to be aged before being sold.

PE

 

[Roger Hicks]

Dear PE,

Thanks,

R.

 

[pentaxuser]

Interesting. Thanks, PhotoEngineer for providing that insight.

The next time I process B&W on a hot summer day and the air conditioning is acting up, I won't worry so much.

Pat I can only speak from one incident but while on a B&W introductory course, I had to use the taps in the print processing room under safelights rather than the film processing room under normal light. I failed to notice the hot and cold taps were the other way around and processed to wash the film( Ilford HP5+ or Delta 400) under the hot tap for probably a couple of minutes before checking water temp. It was just about bearable on the back of my hand!

Result: no damage to the emulsion. So it seems that modern films or at least the above two are remarkably tough.

pentaxuser

 

[GeorgesGiralt]

Dear PE,
You say :
"Today, B&W films are the least hardened of them all to allow dense silver images to form"
Could you please explain to a newbie the interrelation between hardening and image densities ?
I can(t figure it out for myself.
Thanks

 

[Keith Tapscott.]

I would have thought that it was necessary for B&W films to be more durable and robust due to their popularity for press and reportage photography, using 35mm SLR cameras fitted with motor-winds to shoot some subjects (eg: sports) at several frames per second. Also, the use of `roller transport` and `short leader` machines for rapid processing using processes such as Kodak Duraflo RT or Ilfotec Rapid, 45-60 seconds at 26C (78F) being typical.
It seems today that D-SLR`s (cough-spit) have mostly superceded film these days for press photography.

 

[Photo Engineer]

Georges, Keith;

B&W films have always been hard enough for their intended use, but compared to color films, the way silver developed or its form in the coating is more important in B&W than color. In color, the dye image is more important.

So, if you harden too much, the silver that forms will not 'explode' from the grain in just the same way as it will in a less hardened film and will give a different density per unit mass. This is termed 'covering power'. The idea is that you want to get the most image out of the silver.

So, overhardening can lower apparent contrast and speed as well as increase development times. Color runs at 100 F to speed up the processing, but even that might not be enough to allow very hard B&W to form good dense silver images. Also, color is more diffusion limited due to the thickness, but B&W is not.

So, a compromise had to be reached. A lower level of hardener is used in B&W films to allow a good silver image to form and to allow fixation to take place at a reasonable rate without giving a lot of coating defects. And yet the process temperature should not be too high which might give rise to uneven development and other problems.

This is one of the problems with formaldehyde hardening which continues to go on for years and causes soft coatings early in their life, good coatings in the middle ages, and hard brittle coatings late in life with slower speed and higher fog. And, this may be the original source of the myth. The early formalin hardened coatings had a specific optimum life time.

Interestingly enough, I find that my own coatings using gloxal hardening are usable in about 4 hours on paper, but require up to a week on film support to be as hard. I find little change in my paper coatings over a year at room temperature. I have no extensive experience with formalin beyond my first year at Kodak, but I seem to remember pretty much the same thing with the formaldehyd hardened coatings there.

PE

 

[jgjbowen]

PE,

The only time I have heard "aging" in the past decade is with Michael A. Smith and his Lodima paper. He stated the emulsion had to "age" in order to reduce the contrast a bit.

Any thoughts?

Thanks for sharing all of your knowledge and insights with this forum!

 

[PatTrent]

Pat I can only speak from one incident but while on a B&W introductory course, I had to use the taps in the print processing room under safelights rather than the film processing room under normal light. I failed to notice the hot and cold taps were the other way around and processed to wash the film( Ilford HP5+ or Delta 400) under the hot tap for probably a couple of minutes before checking water temp. It was just about bearable on the back of my hand!

Result: no damage to the emulsion. So it seems that modern films or at least the above two are remarkably tough.

pentaxuser

Pentaxuser:

Wow! I'm familiar with the phrase "hot negs" but until now thought it only referred to blown highlights!

Pat

 

[kevs]

Pat I can only speak from one incident but while on a B&W introductory course, I had to use the taps in the print processing room under safelights rather than the film processing room under normal light. I failed to notice the hot and cold taps were the other way around and processed to wash the film( Ilford HP5+ or Delta 400) under the hot tap for probably a couple of minutes before checking water temp. It was just about bearable on the back of my hand!

Result: no damage to the emulsion. So it seems that modern films or at least the above two are remarkably tough.

pentaxuser

I did the same last week whilst processing FP4 Plus. I mistakenly ran the hot tap for a couple of minutes at least - just about bearable to wash hands with - into the dev tank through a hose. No damage whatsoever.

 

[Photo Engineer]

PE,

The only time I have heard "aging" in the past decade is with Michael A. Smith and his Lodima paper. He stated the emulsion had to "age" in order to reduce the contrast a bit.

Any thoughts?

Thanks for sharing all of your knowledge and insights with this forum!

Ummm, well about all I can say is that from the posts Michael has made since, it didn't work.

Now, I can add from personal experience that if you design a good emulsion it will stay good and have the same result over and over and over every time you coat it, but it will eventually go bad with time over a long period. That is inevitable. An emulsion does not normally start bad and become good.

OTOH, if you design a bad emulsion, and here is the key, it starts out looking bad, aging to a point where it may appear good, but then it keeps on going rapidly into emulsion oblivion. Therefore, in a normal situation, an emulsion that started bad and became good in 6 months would eventually become bad in another 6 months or so. (this is a generalization)

As it seems from Michael's posts elsewhere, the emulsion started bad and just stayed there and for all I know is still where it started. It is stable and not right for matching azo, but it is a 'good' emulsion. It is just not doing what was desired and probably never will. From his description it is too fast in speed and too high in contrast IIRC.

PE

 

[erikg]

I have seen from experience that it is much more difficult to get modern films to do things like reticulate, or have partial reversal (the "black sun" effect), and now I know why. Thank you so much for sharing your knowledge, PE. I find all of your posts very interesting!

 

[John Shriver]

PE, any idea what sort of hardener was used in the old ortho Verichrome film, back in the 1940's? Unlike the Verichrome Pan that followed it, it seems to be really unstable, just fogs up completely with age. Or is that a consequence of the bright magenta colored sensitizing dye it used?

(Nothing matches the shelf life of Verichrome Pan!)

 

[Photo Engineer]

It was either chrome alum or formaldehyde. IDK if they used formaldehyde and mucochloric acid at that time. They were transitioning from chrome alum over to formaldehyde.

All emulsions tend to go bad with time due to ambient radiation and heat. I cannot say why the original verichrome went bad, but if it was due to fog, then likely it used a high level of formaldehyde which eventually fogged the emulsion.

PE

 

[noseoil]

PE, curious about the keeping properties of azo paper in general. There have been stories on the web about old boxes from the 30's being good for printing, after storage in less than ideal conditions (heat, humidity, cold cycles, etc.). What was it about azo that made it a unique paper in this respect? Aside from the keeping properties, it was a very good paper with respect to contrast, keeping and image quality in general. It seems that the search for a "new" azo may be tilting at windmills (only due to the constraints of time left for film and paper in the market place).

As an aside, my wife just asked me about any statistics which may exist from cancer in the worker population at Kodak, due to this older chemistry. She had mentioned that she knows Kodak had very strict policies with respect to clothing and protective gear in the 70's. She is a nurse who grew up in Buffalo and was very aware of problems in the Love Canal area (close to home, so to speak). Thanks, tim

P.S. If liability issues exist with respect to internal information, I can certainly understand.

 

[Lee Shively]

I may have a faulty memory, but when Kodak replaced Kodachrome II and Kodachrome X with Kodachrome 25 and Kodachrome 64 back in the 70's there were some stories about the first batches of the film being released before it had properly aged. I do remember having shot some of the new stuff back then and not being particularly happy with the change in the film. Film bought later on was fine and I happily used it for many years. Please correct if I'm mistaken about this.

 

[Photo Engineer]

Oil; Azo is good because it is simple. It is basically a silver chloride emulsion. It does seem to keep well but has other problems that are not readily apparent.

Lee; AFAIK Kodachrome may use formaldehyde, as the formula is so ancient. The orignal 'new' Kodachromes used a prehardener and there was contemplation of increasing the hardener and eliminating this step. IDK how it finally ended up, but that might have given rise to the rumor as the aging on formalin hardened coatings is more critical but only from a hardness standpoint. I've explained the impossibility of making film which requires time to age in. There is no easy way to test for the product to be acceptable then unless one waits. This is extremely difficult.

Imagine if Ford or Chevrolet had to wait 6 months to a year before they were sure if a car was ok to be sold, otherwise it had to be scrapped?

PE

 

[Hologram]

Chrome alum is noted for needing a long time to reach maximum hardness, and formalin requires a long time to achieve the same degree of hardness, but then can continue to harden. The mixture of hardners hardens more quickly and can use less formalin.

In the case of formalin, it goes through an optimum position and then begins to over harden through an effect called afterhardening. This results in brittle coatings and a change in sensitometry plus a growth of fog. The reaction of formalin with gelatin is slow and incomplete, especially at neutral to acidic pH values as is the case with film. Both Haist and Mees describe all of this in their texts, even though some have disputed these facts in posts here and elsewhere.

Chrome alum hardening can be greatly accelerated by heat (at say 50 – 60°C).
And regarding formaldehyde, there's a 1930 French patent (Kodak-Pathé) which seems to have gone to oblivion. It stated that adding phenolic compounds like resorcine to aldehyde had some benefits:
1) the amount of formaldehyde could be significantly reduced;
2) there was no after hardening effect.
The quantities involved were 0.1% formaldehyde and 0.25% resorcine (by weight of gelatin).

The earliest films were not hardened, and since the melting point of gelatin in water is 68 F, that was the reason behind the original B&W processing temperature. Today, B&W films are the least hardened of them all to allow dense silver images to form, but many modern Kodak films can be processed as high as 100 F.

Not sure about formaldehyde but chrome alum hardening definitely goes back at least as far as 1880.

 

[Photo Engineer]

Hologram;

You are right in all cases.

However, heating many coated emulsions to that temperature for the amount of time necessary to harden with chrome alum was certainly bad for the film or paper.

As for the rescorcinol or the like, it was not very good either. The additive actually put into use, as I noted, was muchochloric acid. That was put into use sometime in the mid 1900s. It was totally abandoned, afaik, in about 1970 - 1980. The only holdout at that time was Kodachrome and it may still use that method. IDK.

Formalin was very detrimental at levels needed for processes above 85 deg F. It reacted badly with both the emulsion and couplers in color products.

PE

 

[Hologram]

Hologram;

You are right in all cases.

However, heating many coated emulsions to that temperature for the amount of time necessary to harden with chrome alum was certainly bad for the film or paper.

As for the rescorcinol or the like, it was not very good either. The additive actually put into use, as I noted, was muchochloric acid. That was put into use sometime in the mid 1900s. It was totally abandoned, afaik, in about 1970 - 1980. The only holdout at that time was Kodachrome and it may still use that method. IDK.

Formalin was very detrimental at levels needed for processes above 85 deg F. It reacted badly with both the emulsion and couplers in color products.

PE

Thanks for your reply.


US patent application 20020058215 summarizes a great many hardening agents:


In the method of crosslinking gelatin using a crosslinking agent, all crosslinking agents heretofore known as a hardening agent for gelatin can be used. Representative compounds thereof are described below.

A. Inorganic Crosslinking Agent (Inorganic Hardening Agent)

Cationic chromium complexes (examples of the ligand for the complex include hydroxyl group, oxalic acid group, citric acid group, malonic acid group, lactate, tartrate, succinate, acetate, formate, sulfate, chloride and nitrate);

Aluminum salts (particularly sulfate, potassium alum and aluminum alum; these compounds crosslink the carboxyl group of gelatin);

B. Organic Crosslinking Agent (Organic Hardening Agent)

1. Aldehyde-type Crosslinking Agents:

Formaldehyde is most commonly used. Dialdehyde can also form an effective crosslinking and examples thereof include glyoxal and succinaldehyde with glutaraldehyde being more effective. Various aromatic dialdehydes of diglycoaldehyde, dialdehyde starch, and dialdehyde derivatives of plant gum may also be used for the crosslinking in the present invention.

2. N-Methylol Compounds and Other Protected Aldehyde Crosslinking Agents:

N-methylol compounds obtained by the condensation of formaldehyde with aliphatic linear or cyclic amide of various types, urea or a nitrogen-containing heterocyclic ring. Specific examples thereof include 2,3-dihydroxydioxane, acetic acid esters of dialdehyde and hemiacetal thereof, and 2,5-methoxytetrahydrofuran.

3. Ketone Crosslinking Agents:

Diketone and quinone compounds. Examples of well-known diketones include 2,3-butadione and CH.sub.3COCOCH.sub.3, and examples of well-known quinones include p-benzoquinone.

4. Sulfonic Acid Esters and Sulfonyl Halides:

Representative examples of these compounds include bis(sulfonyl chlorides) and bis(sulfonyl fluorides).

5. Active Halogen Compounds:

Compounds having two or more active halogen atoms. Representative examples of the compound include simple bis-.alpha.-chloro or bis-.alpha.-bromo derivatives, bis(2-chloroethylurea), bis(2-chloroethyl)sulfone and phosphoramidic halide.

6. Epoxides:

Representative examples of this compound include butadiene dioxide.

7. Active Olefins:

A large number of compounds having two or more double bonds, particularly unsubstituted vinyl groups activated by adjacent electron-withdrawing groups are effective as a crosslinking agent of gelatin. Examples of this compound include divinyl ketone, resorcinol bis(vinyl sulfonate), 4,6-bis(vinyl sulfonate), 4,6-bis(vinylsulfonyl)-m-- xylene, bis(vinylsulfonylalkyl) ether or amine, 1,3,5-triacryloylhexahydro- -s-triazine, diacrylamide and 1,3-bis(acryloyl)urea.

8. s-Triazine Type Compounds:

With respect to the compounds of this type, JP-B-47-6151, JP-B-47-33380, JP-B-54-25411 and JP-A-56-130740 describe cyanur chloride-type hardening agents in detail. Also, the compounds having a structure analogous to the cyanur chloride-type hardening agent described in JP-B-53-2726, JP-A-50-61219 and JP-A-56-27135 are useful.

9. Vinyl Sulfone-type Compounds:

The vinyl sulfone-type hardening agent is described in detail, for example, in JP-B-47-24259, JP-B-50-35807, JP-A-49-24435, JP-A-53-41221 and JP-A-59-18944.

10. Carbamoyl Ammonium Salts:

The carbamoyl ammonium salt hardening agent is described in detail in JP-B-56-12853, JP-B-58-32699, JP-A-49-51945, JP-A-51-59625 and JP-A-61-9641.

11. Compounds Described in Belgian Patent 825,726.

12. Amidinium Salt-type Compounds:

The amidinium salt-type hardening agent is described in detail in JP-A-60-225148.

13. Carbodiimide-type Compounds:

The carbodiimide-type hardening agent is described in detail in JP-A-51-126125 and JP-A-52-48311.

14. Pyridinium Base-type Compounds:

The pyridinium base-type hardening agent is described in detail in JP-B-58-50699, JP-A-57-44140 and JP-A-57-46538.

15. Pyridinium Salt-type Compounds:

The pyridinium salt-type hardening agent is described in detail in JP-A-52-54427.

In addition to these compounds, the compounds described in JP-A-50-38540, JP-A-52-93470, JP-A-56-43353, JP-A-58-113929 and U.S. Pat. No. 3,321,313 can also be used as the hardening agent for use in the present invention...

 

[Photo Engineer]

Hologram;

I am familiar with most all of the hardening agents described above. I have tested several of them as a matter of course in my work.

The active chloro compounds require, in many cases, re-application of an activating agent and they released chloride ion, the chloride and some of the epoxides cause side effects with the emulsion. Some react instantly with gelatin and cannot be coated except by extreme methods, and others harden and then are reversed in their action during processing.

It is like any medication, there are side effects. Each company can live with a different set of side effects and have developed work around solutions to them or they don't appear in their coating trials. Kodak's chosen hardener has a series of side effects which we engineers have learned to work around just so we have a hard coating almost instantly when coated.

Fuji, last I heard, used a method entirely different than Kodak used. I have met and discussed this topic with several Fuji and Konica engineers. However, it was done with great care and very obliquely.

PE