3M Photoguard
3M's Photoguard is a coating developed to protect release prints
and negatives from getting scratched and dirty. A film is treated
with the material, which I understand is a polymar coating and
then cured with ultraviolet light. The protection layer of it
adheres to the print. I had quite a number of snipes and trailers
from FILMAC that were Photogard treated and I can personally
attest that the treated film certainly does stay cleaner and
seems to resist scratches much better than untreated film. I also
find that film so treated seems to remain much more resiliant
than untreated film. It feels more supple and softer to the
touch. It doesn't get that "dry", brittle feel that
regular film gets after a number of years.
One side-effect, which some fellow projectionists complained
about, is that Photoguarded film has a tendency to resist splice
tape adhesive. You may have to take a bit of extra care rubbing
the splicing tape on the film. Even without that extra bit of
rubbing, I have never had a splice fail with coated film. Plus,
pealing splice tape OFF a frame of film is much easier with less
adhesive left clinging to the film.
At first glance, the coating seems like a miracle treatmnet --
great advantage to film protection and preservation. However I
have become concerned about the long term effect it may have in
increasing acidosis ("vinegar syndrome") as the coated
print ages. The fact that this treatment is actually a coating
that encases the film raises serious questions as to how much of
the acid gases that the triacetate base material naturally
releases is trapped within the molecular structure of the base.
It has been demonstrated that acetate naturally exudes acid gas
and if that gas is not allowed to escape, its presence excites
the very same chemical reaction that produced the acid byproducts
in the first place. Once the chemical reaction begins, the cycle
is accelerated exponentially if the gasious biproduct is not
allowed to dissipate. The gas itself then becomes a strong
catalyst in the zymurgy.
Keeping triacetate film in tight cans is bad enough, but worst
case scenario is a coating on the film that traps in any acid
gaseous byproducts trying to escape. I hear from other collectors
that coated prints that have typically been
"rejuvinated" by a number of lab processes to get extra
life out of them, turn vinegar and progress very fast. No amount
of "airing out," or neutralizing with washes of base or
alkali baths, seem to stop the process. So much chemical
deterioration takes place that the film will not run through the
projector. The reason given for this happening so swiftly and so
irreversibly on the rejuvinated prints is that the coating that
has been applied entraps the acid byproducts of the chemical
reaction, causing it to cascade within the film base itself
rather than gas-out into the environment (unlike untreated film
where the gases can escape to the air).
(Editor.... the following is a quote of Ashwani K. Mehta,
Business Manager of ScotchGuard Photo and Film Protectors as
reported in the Big Reel 11-15-98)
"...the Image Permanence Institute of the Rochester
Institute of Technology recently showed that the protectors do
allow a film to breathe. They stated that the Photoguard film
protector "does not seal the treated film. The acid
generated in the film base as a result of chemical decay is able
to diffuse from the degrading film even through the
coating.".....If the treated film did not breathe,
delamination would occur. However, no such delamination has
occurred with the Photogard coating..... Our research shows that
the original films coated 20 years ago, stored at room
temperature, look as good as the day they were coated."