Cosmic rays, temperature, and long term film degradation

Want to know from people smarter than myself about how cosmic rays and storage temperature impact film's quality over years.

My film stash, mostly acquired in the mid-2000's with a few 1990's renegades have been "mostly" frozen since then. And within one of those lead bags that a friend in the movie bidness gave me many years ago. I'm sure the lead is too thin to negate cosmic rays, which I hear are one reason film degrades.

Your thoughts and knowledge?

It's likely to be fine, with certain exceptions. Within the last couple of years, I exposed and developed some old Arista house-branded FP4+ and HP5+ that I'd been carrying around, in and out of the fridge, since about 1999. The film looked fine, I don't know if the fog level was any higher than normal (that is I didn't measure it) - the only issue was that the Arista 125 (FP4+) in 120 had some "wrapper offset," meaning the ink on the backing paper left a mark on the emulsion it contacted. This is a known issue and is not a shocker for 20 year old film that spent some time warm.

Temperature is very significant. I doubt that cosmic rays are particularly important. It is likely to get more radiation from nearby natural background sources than cosmic rays, especially if you keep it indoors. For ex, cosmic rays at 30 mrem/yr are only 10% of the US average natural background dose for a person, https://www.nrc.gov/about-nrc/radiation/around-us/doses-daily-lives.html (Caveat: people accumulate some of the background by breathing and eating natural radiation, which film doesn't do, but people also get more cosmic rays because they go outside.)

Lead has high atomic mass which helps it absorb X-rays more efficiently, but I don't think makes as much of a difference with cosmic rays. With all radiation (at natural, not nuclear-reactor, levels), you can make up for material choice by using more of it. In other words, putting the film in a steel filing cabinet is probably just as good as a lead bag, but keeping it in the fridge is more important than either of those.

It is just common sense to keep film refrigerated or even frozen if long-term storage is anticipated. I am currently using up Kodak film at least 20 years old that has been in my fridge. I do believe there is some loss of color saturation and contrast, but not enough to be significant. As far as radiation effecting the film, I would hazard a guess that most freezers and refrigerators would block most forms. After all, it worked for Indiana Jones.

Paul Verizzo said:

I'm sure the lead is too thin to negate cosmic rays

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Good, right on the money. The fun fact about cosmic rays is that they're everywhere, even if you were to store your film in a nuclear bunker underneath a mountain. The lead bag has no other function except to just be in the way when you're getting some film from the freezer. It serves no purpose; perhaps someone is willing to buy it from you on eBay if you market it as 'end of time survival kit to protect brain from hungry zombies'.

Otherwise, heed @reddesert's recommendations. Good that you're storing your film in a freezer; it helps. Don't worry about the bomb, as the movie told us. And at the same time, don't expect any miracles; if I recall correctly you shoot mostly B&W (right?), which is good, but color stock does degrade over time, and badly at that most of the time. Sorry @Larryc001, it's the way of all flesh.

Larryc001 said:

As far as radiation effecting the film, I would hazard a guess that most freezers and refrigerators would block most forms. After all, it worked for Indiana Jones.

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This ain't Hollywood. A fridge or freezer is a thin layer of iron and a bunch of foam. It blocks radiation about as well (probably even less so) as a ceramic coffee cup.

There is not any meaningful action that can prevent cosmic ray damage and unless you are sitting on a nuclear waste dump, you can safely forget about cosmic rays. I have been freezing film since 2005 and I have not had problems with black & white or color negative film. So since you freeze your film, cosmic rays are something that you can forget about.

Not so sure, I just tested a sheet of Kodak Portrait Pan 4X5 expired Nov 1949. I followed up with my paper trail, I bought from a seller in Alaska, it came with a enlarger I bought. Although not frozen in the 15+ years I've had it been kept at room temp, I keep my house at 72 degrees. Today I tested a sheet, Clayton P20, 2 minutes at 70 degrees, standard stop and fix, it is totally fogged. I think that even film that is frozen at some point cosmic radiation will fog it.

I tried to explain this already. Unless you live at say ~10,000 meters ASL (which no one does), naturally occurring terrestrial radiation is a greater source of background radiation than cosmic rays. That may seem like hairsplitting, but it's not. For example, if you have radon in your basement, that likely makes a bigger difference than anything having to do with cosmic rays. Also even the material that you wrap or store your film in has natural radioactivity at a very low level.

However, freezing slows chemical reactions, it doesn't stop them entirely. When you are talking about 70 year old film that's been at room temp for the last 15 years, it's still entirely possible that it was fogged by normal chemical reactions rather than radiation.

The effectiveness of radiation shielding depends on the type of radiation: even a thin layer of material (like a sheet of paper) will stop alpha particles, gamma rays are much harder to stop, but by the same token less likely to be absorbed by the detector (film). Roughly speaking, the effectiveness of radiation shielding scales with the amount of material. At sea level the atmosphere pressure of 1 bar (~15 pounds per sq in, 10^4 Newtons per m^2) means roughly that you are living under that much weight of air. It translates to roughly the same amount of material as ~10 meters depth of water. In other words, the atmosphere is providing ~10 meters of water worth of shielding from cosmic rays (thankfully). Adding a lead bag or other measures to that doesn't do much.

Maybe time makes film foggy as a chemical reaction rather than cosmic rays. Temperature reduces it but probably doesn't eliminate it, unless film is stored at liquid nitrogen levels or lower (-200degC approx).

Food in a freezer deteriorates too.

Do you guys with freezers filled with film have a method of rotating your stock such as shooting your oldest rolls first, or do you shoot the film you have bought recently and keep your old film in the freezer for a rainy day?

Food in a freezer does deteriorate. However this I know. Food is primarily affected by dehydration from the cold and low humidity inside. Poor packaging which allows moisture to get out is no doubt the cause of freezer burn. I don’t see this effecting film sealed in the plastic container that I can barely get open any more! As I have mentioned I am using film that has been just in the fridge for over twenty years. I wish I could get steak to last that long!

faberryman said:

Do you guys with freezers filled with film have a method of rotating your stock such as shooting your oldest rolls first, or do you shoot the film you have bought recently and keep your old film in the freezer for a rainy day?

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I take out the first film that is the type I want.

NASA has measured abnormal neuron activity in astronaut's brains after long space flights due to cosmic rays and other radiation in space . I just use my tinfoil hat to store film in. That helps to keep cosmic rays at bay, and prevents the government from reading my mind.

Larryc001 said:

Food in a freezer does deteriorate. However this I know. Food is primarily affected by dehydration from the cold and low humidity inside. Poor packaging which allows moisture to get out is no doubt the cause of freezer burn. I don’t see this effecting film sealed in the plastic container that I can barely get open any more! As I have mentioned I am using film that has been just in the fridge for over twenty years. I wish I could get steak to last that long!

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OK, leaving food aside, can a chemical reaction leading to film fogging take place at domestic freezer temperatures (say -10 or -15 degC)? There would be some atoms around with nothing much to do, such as some O2, CO2, H20 even if there's very little of them.

john_s said:

can a chemical reaction leading to film fogging take place at domestic freezer temperatures (say -10 or -15 degC)?

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Yes. Only if you take temperatures down to absolute zero (0 K) we'll have a different story on our hands. So film stored in the freezer for decades will still deteriorate - only much slower than at room temperature.

Film degradation is basically chemical reactions.....which are speeded up by a number of factors....or slowed down.

Chiefly temperature....all chemical reactions including what happens to photographic emulsions over time are speeded up by higher temperature. So freezing is of huge benefit. Added to this the freezer is dark, which can only help compared to, say, storing your films on a sunny windowsill for 30 years.

Film speed is also a big factor. The higher the ISO, the faster the damage.

B&W film lasts much longer than colour film.

As for background radiation, the lead container should see to that. The metal casing of a fridge will mitigate this somewhat too....especially any alpha particles.

Cosmic rays are a different matter because they are made up of all manner of high energy particles including electrons, various nuclei some of which are radioactive partoc;es and some are not. Lead will protect against the radioactive particles but not the others. However, the damage is cumulative (ie happens over time) and is very slow because the concentration of cosmic rays is not high. My own work with radioisotopes includes demonstrating the shielding effect of various materials with alpha, beta and gamma sources....a good 5mm of lead will cut out all of the alpha and beta, and 90% of the gamma.

In practise, B&W film can be frozen for 40-50 years and come out fresh as the day it was purchased. Colour negative film at least 20 years. Colour reversal is a bit of a crap shoot but even at 20 years old you'll get images even if the colours have shifted.

There are people out there shooting 100 year old glass plates which haven't been refrigerated and getting decent photos.

Additionally....everything @reddesert said.

The only other caveat is humidity. Store film, especially roll films with backing paper, in their sealed foil containers from the factory. Do not open them until the film has come up to room temperature, at least an hour after the freezer. I often leave overnight to be sure. Even then, some of the bad batches of film produced in recent years might have backing paper issues.

I stored some unopened 35mm Tmax-400 (TMY, not the later TMY2) in the freezer for around 10-15 years. Both rolls were moderately fogged. Whatever the cause, I conclude that age fogs film. Fast film anyway.

Mark Overton

momus said:

NASA has measured abnormal neuron activity in astronaut's brains after long space flights due to cosmic rays and other radiation in space . I just use my tinfoil hat to store film in. That helps to keep cosmic rays at bay, and prevents the government from reading my mind.

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