3.
KNOW YOUR ENEMY: DAMAGE AND DECOMPOSITION
3.1 DETERMINING AGE
3.2 MECHANICAL DAMAGE
3.21 Tears
3.22 Perforation Damage
3.23 Scratches
3.3 BIOLOGICAL DAMAGE: MOLD, MILDEW, FUNGI
3.4 CHEMICAL DAMAGE
3.41 Nitrate
3.42 Acetate: Vinegar Syndrome
3.43 Color Fade
Film is subject to three main categories of deterioration: mechanical, biological, and chemical decay. Causes of damage and decay will be discussed in this section, and the main techniques to control film deterioration will be identified.
3.1 DETERMINING
AGE
Although the condition of a reel of film is not necessarily dependent
on its age, it is often helpful to know how old a piece of film is. One
method for identifying the age of a film is to look for its manufacturer's
date code. Kodak prints a series of small shapes along the edges of its
film. These codes identify
the date the film was manufactured, but remember that sometimes it may
have been several years later that the film actually went through a camera.
Also be aware of the fact that Kodak's codes run in twenty-year cycles,
so the code for 1955 is the same as 1975. You will also have to look at
the image and use other clues to determine its age. Finally, if you are
looking at a copy and not the original, determine which series of codes
you are reading, as you may be able to see more than one generation. Older
codes may have been printed through in the laboratory printing process.
Note all codes, and use the most recent one to determine the age of the
piece of film you're looking at.
3.2
MECHANICAL DAMAGE
3.21 Tears
Tears and breaks are usually the result of mishandling of film
during winding or projection, or of old splices coming undone. All breaks,
tears and weak splices need to be repaired with cement or tape splices.
3.22
Perforation Damage
Another common type of damage is torn perforations (perfs). This is usually
caused by improper threading of the film in the projector, and is usually
found at the beginnings and ends of reels or after a bad splice. The best
way to avoid further perforation damage is to always be sure to use sufficient
leader (at both the heads and tails of reels). Repair all faulty splices,
thread the film carefully in a clean, properly lubricated projector, and
do not attempt to project shrunken or brittle film.
3.23 Scratches
Either side of the film may be scratched by contact with dirt or worn
rollers in the film path during projection. Scratching and abrasions can
also occur outside of the projector if film is wound too tightly or loosely.
Scratching may have occurred at the lab, in the camera, or during the
editing process. Never pull the end of a reel of film to tighten it up
on the reel or core. This is an easy way to scratch your film. While there
are film treatments to "rejuvenate" films by applying protective
coatings or lacquers, we do not recommend this because possibly harmful
chemicals are involved. Base-side scratches can be minimized during the
duplication process (either film-to-film or film-to-video telecine) by
the use of the wet gate method, in which the film passes through a liquid
solution that temporarily fills in the scratches so they do not show in
the resulting copy.
3.3 BIOLOGICAL
DAMAGE
Mold, Mildew, Fungi
There are types of damage that can occur even while the film remains in
storage. Improperly stored films, especially those in hot and humid climates
or damp locations such as cellars or garages, are prone to attack by mold,
mildew and fungus. These organisms can cause severe damage to the emulsion,
and while they generally attack the film from the edge, they can easily
make their way into the roll, sometimes resulting in dull spots or feathery
tendrils on the image. Providing proper storage minimizes the risk of
biological decay. This might be achieved by just avoiding sustained high
humidities, typically during the summers, and by improving ventilation.
3.4 CHEMICAL
DAMAGE
Film components such as film supports (e.g., nitrate and acetate)
and color dyes are inherently subject to chemical deterioration.
3.41 Nitrate
Decomposition
Cellulose nitrate film base is prone to chemical decay over time. The
condition nitrate films are in today is a direct result of the conditions
under which they were stored, as well as how they were manufactured.
Nitrate decay is
described in terms of 5 specific stages. These descriptive stages are
a widely recognized standard.
Stage 1: Film has an amber discoloration with fading of the image. Faint noxious odor. Rust ring may form on inside of metal film cans.
Stage 2: Emulsion becomes adhesive and the film tends to stick together during unrolling. Faint noxious odor.
Stage 3: Portions of the film are soft, contain gas bubbles, and emit a noxious odor.
Stage 4: Entire film is soft and welded into a single mass, the surface may be covered with viscous froth, and a strong noxious odor is given off.
Stage 5: Film mass degenerates partially or entirely into a shock sensitive brownish acrid powder.
3.42 Acetate
Decomposition: Vinegar Syndrome
Acetate base film is subject to the so-called vinegar syndrome.
The term 'vinegar syndrome' is taken from the distinct odor that is given
off by deteriorating acetate film. Vinegar syndrome results from a chemical
reaction that takes place at the molecular level that can cause serious
and irreparable damage to film. When combined with moisture, heat, and
acids, the plastic support in the film begins to release acetic acid.
The process is an autocatalytic one, meaning that once the degradation
begins it starts to 'feed upon itself' and the deterioration process begins
to snowball. When film reaches its autocatalytic point the acetic acid
released by the film grows exponentially, and with it the potential problems
for the film. Climate is an important determining factor in the deterioration
because humidity affects the amount of water absorbed by the film and
heat supplies energy for the chemical reactions. Even more important is
the "micro-environment," a term used to describe the conditions
inside the film can. Vinegar syndrome appears to be contagious, so any
film suffering from it should be stored apart from "healthy"
reels.
The vinegar smell
is the most obvious indicator of decaying acetate film, but it is by no
means the only one. The condition of the film can be evaluated by using
acid detector strips (e.g., IPI’s A-D Strips); this approach provides
an objective way to determine the state of preservation of the materials
and their needs to be further stabilized. White powder on the edges of
the film may indicate plasticizers loss. Because of the molecular breakdown
of the plastic base, in advanced stages of deterioration the film becomes
brittle and shrunken. Films with shrinkage of more than 1% could be damaged
by projector mechanisms, so should not be projected. [See
section 5]
There are techniques for re-dimensioning film (restoring it to a less-shrunken
state), but these are temporary measures that can permanently damage the
film and should only be done in a lab situation as a last-ditch method
to enable a new negative or print to be made.
Acetate Decomposition—Advanced
Stages of Decay
The typical pattern for acetate decay is:
1. Vinegar odor
2. Shrinkage
3. Cupping: the film retains a curve. It will not lie flat, but instead appears wavy.
4. Crazing: the emulsion cracks and the image appears as a crazy mosaic.
5. Appearance of white powder on edges (from binder deterioration, this is the plasticizer separating from the film).
6. Film becomes square on reel [Illustration].
7. Film is no longer flexible and the emulsion flakes off from the base.
3.43 Color
Fading and Decomposition
Color fading and other forms of chemical decomposition are usually the
results of inherent problems in the manufacturing of the film, bad processing
or poor storage conditions over the years. Generally there is nothing
that can be done to reverse the process of color fade. However, you can
stop further damage to the film by moving it into good storage conditions
(see section 8).