You are correct, "safety film" refers to cellulose acetate
film as opposed to cellulose nitrate film. Nitrate burns
intensely and provides its own oxygen so is very difficult to
extinguis. Also, once nitrate begins to decompose it can combust
spontaneously. Acetate film will support flame but will not
spontaneously combust.
Nitrate motion picture film has not been made since 1951 and
most other formats on nitrate were discontinued long ago. 16mm
and 8mm motion picture film were _never_ made on nitrate base.
It is the color sensitivity of the emulsion that determines
if it can be processed using a safe light. Plain emulsions are
sensitive to blue and near UV and orthochromatic emulsions are,
in addition, sensitive to green and sometimes yellow light. They
can be processed under a red safelight although some ortho films
have enough far yellow sensitivity to require a very weak red
light or restricted time. Panchromatic emulsions are sensitive to
red light and can be processed only in total darkness. Some can
be processed in very dim green light for short periods of time.
The green light of a color where the sensitivity of the dark
adapted eye is at its maximum. In addition many panchromatic
films have a dip in their sensitivity to green light.
There are desensitizers that reduce the red sensitivity of
pan film and allow more extended processing under a rad safelight.
Now, since I am being wordy, the method of processing will
have no effect on this film. The problem is that its been bent or
folded beyond the elastic limit of the support. While film
support does absorb some moisture it is not like the emulsion,
which absorbs a lot. Soaking it may result in softening the
emulsion enough to cause it to separate from the support. If you
want to experiment with floating it onto a new support this may
be useful but otherwise I think it will make a difficult problem
worse.
On 3/5/2020 2:41 PM, Ken Hart wrote:
Unless I'm mistaken (I've been mistaken before!), "safety film" refers to the flammability of the film base, and has nothing to do with a safe light for processing.
From Google/Wiki: "Cellulose acetate film, or safety film, is used in photography as a base material for photographic emulsions. It was introduced in the early 20th century by film manufacturers and intended as a safe film base replacement for unstable and highly flammable nitrate film."
Ken Hart
kwhart1@xxxxxxxxxxxx
On 3/5/20 4:50 PM, mark@xxxxxxxxxxxxxxxxxx wrote:
Had that happen once too. In that case though I knew what was on it, and although there might have been some interesting flower pictures lost, that would not be nearly as bad a losing one that had your great grandmother on it when she was young.
I'm wondering if a film scanner that feeds from the sprockets could get the film flat enough. My flat bed with its holder I am sure wouldn't. Got two labs that might be able to do it. Anyone recognize 3LIM or 31IM? It is a safety film, which might mean this film could have been processed under a safe light. My search has turned up nothing. Just knowing that might be an important piece of information.
-------- Original Message --------
Subject: [pure-silver] Re: Old film that needs to be flattened
From: "Laurence Cuffe"
<dmarc-noreply-outsider@xxxxxxxxxxxxx
<mailto:dmarc-noreply-outsider@xxxxxxxxxxxxx>> (Redacted
sender "cuffe" for DMARC)
Date: Wed, March 04, 2020 7:06 pm
To: pure-silver@xxxxxxxxxxxxx
<mailto:pure-silver@xxxxxxxxxxxxx>
On 5 Mar 2020, at 00:21, mark@xxxxxxxxxxxxxxxxxx
<mailto:mark@xxxxxxxxxxxxxxxxxx> wrote:
Doing a project with very old family photos. I have a
strip of 35mm negative that on it says safety ILM 3 I
think it is, but that isn't the biggest problem. It was
over the years creased like paper that had been folded.
Some of the folds are through the middle of the image.
Any way to flatten.
I have no idea what is one them. Judging from the prints
found with it, I would wager a best guess of about 50
years. They don't appear to be scratched up.
First idea is to contact print them with glass on top to
see what I have. I could probably copy them from a
contact print, but would rather have the wet print if
possible. Would leaving them sandwiched between two
plates of glass with some weight on top do any good.
Though about soaking them, but thought better of that
pretty quickly. Might or might not help. Ideas and
thanks everyone
I’d second your instinct that soaking might not be ideal.
I have had some poor experiences where old emulsion just
sloughed off the substrate when trying to clean old
negatives with water.
Best
Laurence Cuffe
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