I do my PhD in chemistry and I thought I'd put together some thoughts and facts about the vinegar syndrome, although I'm not a specialist in the
field of polymer chemistry
Anyway film consists of the following parts:
a) The base
b) The gelatine
c) The dyes or the silver
d) additives
As most of you might know the VS comes from the base:
a) To my knowledge there are three kinds of bases:
I. Nitrate base
II. Acetate base
III. Polyester (Mylar/Estar) base
The Nitrate Base and the Acetate Base are in fact quite similar. Polymers
consist basically of long chains of more or less hydrogenated carbon.
Depending on the needs the polymer has to fulfil there are either other
atoms than carbon in the chain and/or there are "side arms" with specific
groups of atoms at the ends. Nitrate and acetate film base consists of
modified cellulose i. e. it's like rings of carbon atoms chained together
to a long chain and as a modification it has either a nitro group "side
arm" (-NO2) or a acetyl group "side arm" (-OCOCH3). These side arms are
needed to create the specific properties of the plastic, so they can't
just be left away.
The problem is now that these groups can under certain circumstances
(we'll get to that!) be detached from the rest of the chain and form
(tadaaa!) Nitric acid (HNO3) for nitrate film and Acetic acid
(CH3COOH) for acetate film. Nitric acid is much much stronger than Acetic
acid. Acetic acid is the stuff that makes vinegar sour (in vinegar there
is about 5% of it) and Nitric acid is the stuff that makes acid rain
(besides from Sulfuric acid) evoked by fumes from cars and industry.
Polyester is a different plastic which seems not to degenerate (well,
I guess it does it too, but much much slower..)
As you know the deorientation i.e. VS starts with a acidic smell that gets
stonger. It's effects on the base are that it will give out vinegar and
shrink and turn brittle.
b) The gelatine is a thin layer on one side of the film where all the dyes
and silver are enclosed (i. e. the picture). Gelatine is quite tough and
does not change for very long period of time.
When treated with acids it can soften. That's why Nitrate film that has
the syndrome turns sticky. Acetic acid is not strong enough to do that
(only in extreme cases where everything's lost anyway).
c) The dyes are a problem themselves. Many films change color without
having the VS ( but I won't go into that).
There are almost no nitrate films with color. The silver (b/w films) turns
orange red through nitrate decomposition (nitritic acid is a strong
oxidizer).
The VS has mostly an effect on the color of acetate film (mostly
"enhanced" fading). There is almost no effect in b/w prints. That's why
often the base shrinks and turns brittle while the gelatine & color would
still be OK. In photography it is a technique to save pictures by pulling
off the (very thin!) gelatine layer and putting it onto another base. A
very difficult procedure.
d) There are two mayor additives in the film base one are chemicals who
again optimize the properties of the plastic (plasticisers)* and the other
are "invisible" dyes which help to get rid of "halo effects" when
projecting. When the VS starts, those chemicals can come out of the
plastic and form "bubbles" inside the film or between the gelatine and the
base. The bubbles are either filled with liquid or small cristals.
The anti-halo-dyes which are transparent can become coloured (pinkish or bueish).
Another additive is for example stuff with which the film is coated. This
can pose a problem because it will make the film stop "breathing"
(->Disney). Otherwise I don't know anything about that.
* some of them help to reduce flammability of the film
SO, WHAT DOES TRIGGER THE VS????
Mostly it is humidity because it takes water to turn the acetyl group into
acetic acid and heat (that always helps with chemical reactions). There
are probably many other possibilities (most of them still unknown to
science). What I try to say is that I think there is no way to exclude the
possibility of the VS, you can just get the probability down as low as
possible. Because it affects the base it can start on the inside or on the
outside of it! Afer all I would guess mostly on the outside because that's
where the film is exposed to the stuff that triggers the reaction. I
predict that there will never be an absolute cure for the VS (I also
predict Doomsday on 29th of February 2001 and I can read from your palm
for a small fee). The main bad thing is that you must not take all the
humidity away from the enviroment of the film, it needs some to stay well.
Safest option would be deep freezing I guess (but who has got a freezer like
Schwarzenegger alias Mr Freeze?).
That's quite frustrating for so much reading, right?
If a film has caught the VS it is best to remove as much acid as possible,
because the acidification process is again catalyzed by the acid it
produced! It will get worser and worser (just to say it in correct English)!
Removing acid is not easy, specially because it will also be inside the
film and so a thorough treatment would need to go through and through.
Store the film out of a box so the acid can get away.
You guys know more about the mysterious Filmrenew substance...
I would rather not recommend using sodium or potassium hydroxide (NaOH,
KOH). Apart from being very poisonous and agressive I guess they can also
affect the dyes in the gelatine (?).
That's what I know, friends. I hope it was understandable and could give
a picture to those who wanted to know.
Finally I can say black and white movies on polyester film will last
longest. Who wants colors anyway? The best films are in b/w!
Ooops, I'm getting a bit non-scientific there
I'll try to continue my discourse on the VS and it's treatment based on
the questions Frank has asked. Still I'll do my best to be correct, but I
won't guarantee it (dematerialized films will not be refunded).
Frank basically proposed four ways to defeat the VS:
I. Using Molecular Sieves
II. Creating A Vacuum
III. Using An Alkaline Gas (Alkali=Base)
IV. Using An Alkaline Bath
V. Using Witchcraft... ah... no... waitasecond
I. Molecular Sieves (MS)
What is it?
MS are compounds which have a huge surface with lots of tiny "holes".
Depending on the size and shape these holes certain kinds of Molecules
will fit into them and other will not. So the MS will function as a
selective kind of sponge. There are many different kinds of MS designed
for oil, water or whatever one wants to get rid of...
The MS by Kodak are made to soak up the acetic acid (AA) which is
outgassed by the acetate base (also a "healthy" print does outgas some AA).
Does it work?
There seems to be quite a discussion going on on how much it really helps.
The main problem is that the MS will also take up water (it's a molecule
of a similar size). Because water is more abundant, most holes will be
"plugged" by it and not the AA. Only if the general humidity is very low,
it will work as desired.
There is another point which I will discuss later...
But there is no question that molecular sieves will help to PREVENT the VS
(also because they take up the water). Using such materials it's always
useful to follow excactly the guidelines of use given by the manufacturer!
Other materials with similar features
There are many different materials that are hygroscopic (they take up
water). They might work to a certain degree, but they are not designed for
your use and so noone will guarantee their usfulness. On the other hand:
if it reduces the odour that means it has worked to remove the outgassed
AA (and the MS will not do more than that). So I would say it is an
alternative (many times industry sells us something which could be
replaced with something much cheaper, they just don't tell us)
II. Vacuum
Two ways of evacuation would be possible:
a) Putting the print into a floppy container (like a plastic bag) and
pumping the air out. Your film will be vacuum packed like the chicken
in the supermarket.
I would consider this a bad idea because you stop the film from
breathing, and thats not good (also for a "healthy" print). Because the
AA gas comes from the inside of the base you will just trap it and
increase the catalithic process of deorientation.
b) Using a rigid container and pumping the air out. The container must be
really rigid! Otherwise the air pressure will crush it and you'll cause
an implosion...
Doing it in this way, all the volatile substanced in the film will be
"pulled out". Mainly water and the AA I guess. This is like what the
molecular sieve does just a bit more radical. I'm really not quite
shure what it would do to the film on a longer term...
The main problem here is that keeping up a good vacuum on a relatively
big space is neither easy nor cheap.
IV. Alkaline Gas
Please keep in mind that dealing with gases it alwas quite tricky and dangerous!
An alkaline gas would definatively destroy all the AA which is outgassed
by the film. The only alkaline gas which I can think of at the moment is
Ammonia (NH3). But as you might know, even thinking of Ammonia will burn
your eyes and nose away, so it is no option (it's a: don't-try-this-at-home!).
I will come back to gases a bit later..
IV. Alkaline Bath
Baking soda dissolved in water was suggested. Dissolving baking soda does
give small amounts of Sodium Haydroxide (NaOH) which is a strong base
(maybe you remember the discussion about it on FCLS). So putting the film
into such a solution will destroy some of the AA for sure.
Using water on film:
The developing of the film is also done with chemicals dissolved in water,
so water is not a priori a threat to film. I think it is just important
that it is removed from it within a reasonnable time.
A alkaline solution in another solvent might be a better choice. But I
have no idea what to recommend. And there we come to one of the main
problems for us. Such things have to be tested in reproducable scientific
experiments. Doing this in your basement at home without a thorough
knowledge of what you are doing and without the suiting equipment will
PROBABLY do more harm than good and in the worst case affect your health.
A general note about using chemicals on film:
Because the film itself consists not only of the acetate base but is a
quite complex system of different compounds it is difficult to predict the
influence a chemical has on it. What does it help if you can stop the VS
with a certain chemical but the same stuff will eat away the dyes?!
A general note on the treatmants mentioned above:
In my last posting I assumed that the "vinegar process" would mainly start
and take place on the surface of the base. I was wrong (it happens!). The
process seems to take place mainly inside and then the AA which was set
free wanders to the surface (diffusion process) where it is outgassed. On
its way through the acetate layer it will catalyse more of the process
and just taking it away when it comes out will not help a great deal
because most harm has already been done (although removing stuff from
the outside is better than nothing, that's shure!). So using molecular
sieves, vacuum would only remove the outgassed stuff. And a gas or a
liquid that does not penetrate the base will not do much more. I can
imagine that a gas like ammonia would penetrate the film and also some
liquids if left to soak a while. This has still to be found out. I am
searching for scientific publications where such experiments have been
done, but havn't found anything yet.
And there is ONE LAST PROBLEM even with a gas or liquid that would<
penetrate the base: If it reacts with the AA inside the layer it will
most probably be stuck there. The product of the reaction might not be
transparent and the treated film will turn out foggy or get a "colour"!
Maybe I'm making this all too complicated in my mind but I'm just trying
to think of everything. That's just the kind of problem we're dealing with here!
One LAST remark:
The three stages of the VS:
1. It hasn't started yet
2. It started but the film still runs fine (only small damage)
3. The damage is so great that the film can't be run anymore
Stage 1: Good
If you can halt the deorientation in stage 2 with whatever treatment: Good
If you would manage to stop the VS only at stage 3 it won't help too much
because stopping it does not mean that the damage is being repaired!
It is virtually impossible to "repair" a damaged polymere structure.
Some of the available products to treat damaged film probably contain softeners
for polymers which will make the film smoother so it can be run again.
This is only a solution for a limited period of time.
So, if you ask me: A really damaged print is lost.
OK I lied: this is the last remark:
* It will always be hard to save a film which caught the VS
* If there was a good treatment, doing it would probably cost as much as
purchasing a new print.
* So the goal must be: prevent it!
The main problem with preventing is not that we would not know how to
prevent the VS, but that most of us don't have the cash and/or the
facilities to store our films after these guidelines.
