Safety of collecting old slides

Concord_850 · Oct 19, 2022

I collect old colour slides from time to time. Mostly Kodachrome. I always assumed that any slides I acquire are safety film rather than nitrate. But when I think about it I don't know this for certain, so can anyone give or point to information about whether Kodachrome or other relevant stocks were ever issued on nitrate bases? I only learned recently that nitrate continued to be used in motion pictures until the 1950s, which was a lot later than I thought. I believe early home movie film, 16mm and 8mm, was safety film from the outset, but was this the case for consumer still film also?

ntenny · Oct 19, 2022

The US National Park Service say Kodachrome was on a cellulose acetate base from the time it was introduced in 1935:
https://www.nps.gov/museum/coldstorage/html/filmid2_1.html

They also say that you’re right that nitrate was never used for 8mm or 16mm.

-NT

Concord_850 · Oct 19, 2022

Thanks for the link!

AgX · Oct 19, 2022

Revenant said:
I always assumed that any slides I acquire are safety film rather than nitrate.

Your assumption is wrong. It depends on manufacturer and manufacturing period.

Keep in mind that in home projection basically there is less heating of the film, and the lesser the larger the format. But I understand that you see a connection between cine and still projection.

BAC1967 · Oct 19, 2022

I have some old negatives on Du Pont 5948 Nitrate film that could have been bulk loaded from 35mm movie film. I'm not sure if it was ever sold as a consumer film.

Picking a Pineapple by Bryan Chernick, on Flickr

I also have some expired French made Kodak Super-XX Nitrate film in 9X12 that I shoot. There's no expiration date on the box, it could be from the 1950's, unless they were making Nitrate in France longer than the U.S.. The film was for Tri-Color Photography, probably not a consumer film.

Long Pier by Bryan Chernick, on Flickr

For safety I store this film in metal containers in metal cabinets. Like anything flammable, you want to keep it away from an ignition source.

AgX · Oct 19, 2022

A mounted nitrate base slide is about the most safe form of such films as due to the ventilation most likely self-ignition is prevented.

Concord_850 · Oct 20, 2022

Thanks for all the replies.

GRHazelton · Oct 23, 2022

Here is a link to material from the National Achives: https://unwritten-record.blogs.arch...rvation-101-is-nitrate-film-really-dangerous/
The Library of Congress has good information on nitrate film storage, as it does for proper preservation of other photographic media. Here is a link to L of C's information on film storage: https://www.loc.gov/preservation/ca...mperature as,relative humidity between 30-40%
From a personal perspective: Decades ago, I was in my early teens, my Father and I (he was a PhD ChemEng from U of Michigan) were setting up a home darkroom. Holding a roll of film, probably 120 or 620, we went outside where he tacked the film to a board. Then, carefully, he lit the film. It burned incredibly rapidly. He then said that movies, back in the day, used such film for theatical presentation........ Imagine such a fire in a projection booth.

Alan Edward Klein · Oct 24, 2022

GRHazelton said:
Here is a link to material from the National Achives: https://unwritten-record.blogs.arch...rvation-101-is-nitrate-film-really-dangerous/
The Library of Congress has good information on nitrate film storage, as it does for proper preservation of other photographic media. Here is a link to L of C's information on film storage: https://www.loc.gov/preservation/care/film.html#:~:text=Keep the ambient temperature as,relative humidity between 30-40%
From a personal perspective: Decades ago, I was in my early teens, my Father and I (he was a PhD ChemEng from U of Michigan) were setting up a home darkroom. Holding a roll of film, probably 120 or 620, we went outside where he tacked the film to a board. Then, carefully, he lit the film. It burned incredibly rapidly. He then said that movies, back in the day, used such film for theatical presentation........ Imagine such a fire in a projection booth.

When I was about 11 in public school in 1956ish I was on the squad that showed 16mm sound movies in the auditorium. We used to hang out in the projection room where all the film and cameras were kept. I don;t recall instructions about film fires or the danger thereof. Maybe they were all converted by then. But there were always mice in the garbage can in the booth eating or carrying away the bits of film we'd throw in there after splicing film when it would break.

guangong · Oct 24, 2022

My gigantic tome on film preservation from Kodak states that nitrate film preservation depends upon proper storage, and is about the same as safety film.
60 yrs ago I was lucky enough to see silent films projected on nitrate. Being on a crystal clear base, the films were quite stunning. Acetate base not as clear. Films later transferred to safety film lack that glow.
Most slide projectors have a heat absorbing glass that protects slides, so even nitrate slides should be ok. Keep in mind that in early days projectors were illuminated by flame and not electricity.

Sirius Glass · Oct 24, 2022

All my slides were shot after all the film had become safety film, so I can sleep at night and not worry about film safety.

Concord_850 · Oct 24, 2022

Thanks again.

This document has the following interesting remark:

Although some believe that nitrate can spontaneously ignite if it is stored for a long time in very hot and dry conditions, no-one has ever been able to prove this for sure and suspected incidents are rare. Almost all fires begin after a reel has been ignited by another source, usually involving human error.

Which makes me a little less afraid than I was, although the slides I'm worried about are in glass mounts, so that might be the sort of "human error" that could lead to ignition, as the film "must be allowed to breathe and off-gas".

I think I'll settle the matter by cutting off the perforated edges of one slide and setting them alight outdoors at a safe distance. It's colour reversal film apparently from the 1950s, but worryingly there seem to be no edge markings.

Correction: One of them at least is marked "safety film"; some others are "Agfacolor".

MattKing · Oct 24, 2022

A slide in a glass mount isn't likely to burst into flame.
And it quite difficult to pack enough flammable material into the necessarily small volume to create a conflagration, if there are also glass slide mounts in there!

Alan Edward Klein · Oct 24, 2022

I remember some slides melting in my projector or when my 8mm film stopped moving in my film projector. Couldn't they catch fire if they weren't safety film?

Safety film of the 1980s - Ektachrome 64.

Sirius Glass · Oct 24, 2022

Alan Edward Klein said:
I remember some slides melting in my projector or when my 8mm film stopped moving in my film projector. Couldn't they catch fire if they weren't safety film?

Safety film of the 1980s - Ektachrome 64.

Someone went to the Grand Canyon and Monument Valley.

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