"Kodak 4 Safety Film" -- Is this nitrate based?

[Ulophot]

I offered to print some 1972 negatives for a friend and picked them up today. He is originally Mexican, these were shot there, and the negatives say, "Kodak 4 Safety Film." I looked because, when I removed them from the aging glassine envelope, I found that while 3 of the 6 strips look normal, though underdeveloped, the image (not the base) of others is yellowish-green rather than black.

I first thought they might have been improperly fixed, so a clipped one neg and fixed; no change. I washed it and put it in a selenium intensification bath (AA's formula) for 5 minutes. The result is very little intensification and change to a brownish image, which at least indicates, I assume, that the toner did its usual job.

Anyone seen something like this and know what's going on here? I'm leaning toward intensifying the rest of the negs, since they're very thin to begin with.

My enlarger is LED diffusion, so I don't expect heat problems if the base is indeed nitrate, but I will be most grateful for any cautions/advice on handling.

Thanks.

[Michael R]

“Safety Film” is a reference to the base not being nitrate.

[Drew Wiley]

'Safety Film" means it's NOT nitrocellulose based. Nitrate film was discontinued long before the 70's, and you don't want to even store it. No telling what the discoloration is. Could be from improper developing, fixing, or improper storage, even hypothetically from the kind of glassine itself.

[Ulophot]

Thank you, Michael and Drew, for the extremely prompt responses. Remind me to give you a raise next year. I was pretty sure the nitrate had been long-since discontinued, but since it was in an under-developed country, I wanted to double-check.

I'll proceed with the selenium treatment.

[Ron in Arcata California]

Don't know when they quit, but it was a lot later than most people think.
I have shot this and the film was in perfect condition. Expiration date is May 1956.

The real nitrate problem is with old motion picture film. Stored in sealed metal film cans the shear volume of film is a serious fire hazard. Sheet film separated with PH neutral paper and kept cold is not a big issue. The hard part is explaining this to the fire marshal. They only hear the word "nitrate" and it's end of the story. Too many historic negatives have been destroyed because there wasn't enough money to have them properly printed on archival material or digitally scanned.

[Kevin Crisp]

We all thought back in the day that glasseines (sp?) were the ultimate negative protection. They were OK, but in the long term can have problems. They turn yellow brown, and if exposed to heat (admittedly abusing them) they can tint the image and, worse case, stick to the emulsion.

[Ulophot]

Well, I have discovered that the images are unstable. The yellow apparently indicates a chemical change (physical? I never could remember the difference), such that fixer actually starts eating the image. Unfortunately the small amount of fixer, or thiosulfate, in the selenium toner seems to outpace the selenium. And, on a neg that I had not fixed and only toned, a silvering started to appear, i.e., a shiny silver clouding, like old prints silvering. So, after a couple of negs so affected, I am simply going to make the best prints I can from the other film as-is. Probably Gr. 3 1/2 -5, with careful balancing. At least I can tone the prints. If he wants to track down a conservator, he can.

[Drew Wiley]

Museums all across the West had to destroy piles of historically significant nitrate negatives or else lose their insurance, or have their doors shut by the local fire dept. Some managed to make token prints of a few select examples first. Properly storing them requires hermetically sealed refrigeration. Only Hollywood archives have sufficient funding and equipment to efficiently copy many old films onto newer safer base, if the original negs aren't starting to decompose yet (when they really get dangerous).

[domaz]

Some of my grandparents negatives were nitrate base. We learned quick that if the film rebate didn't say "Safety Film" they were Nitrate film. Took a few reject negatives out in the yard and set them on fire to confirm. Just a few 35mm negative strips burned with the intensity of basically an equivalent volume of gasoline. Quite impressive and scary.