The myth about film and paper aging
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.
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.
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.
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.
Originally Posted by Photo Engineer
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.
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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.
Last edited by Photo Engineer; 03-17-2007 at 04:39 PM. Click to view previous post history.
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!
Originally Posted by PatTrent
Result: no damage to the emulsion. So it seems that modern films or at least the above two are remarkably tough.
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.
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.