Film Cleaning
An Introduction
Film can be cleaned by a number of different methods, by water, by organic
solvents or by adhesives. Cleaning of all film between the various stages of
restoration is essential, but it is necessary to recognise the differences
between cleaning as carried out by conventional film laboratories and cleaning
of archive film.
Fresh negative film in modern laboratories is always cleaned between each
handling or printing stage using a solvent in an ultrasonically vibrated bath
to remove dust, fingerprints and minor dirt particles. The procedure is one of
ensuring that nothing is present that could impair the printing process and be
seen on the print as "sparkle", tiny spots of clear film where a
speck of dust was stuck to the film, or be a source of abrasion.
Cleaning archive film for the first time can be as simple as this, but
archive film is frequently unbelievably dirty; so dirty that it would seem that
it had never been cleaned in it's life, which is often the case. Projection
prints that have been on a cinema circuit could have had almost anything done
to them from being covered in split coffee to being run onto the projection
room floor because the take up system broke [very common].
Early silent films that have not been touched for many years may have so
much applied grime that a cleaning process may remove measurable amounts of
material. In one such case, a well-used 5 min [500 ft] Pathe Pictorial print of
1952 weighed 12 gm less after ultrasonic solvent cleaning! The subject of
cleaning is complex and the following issues are special to archive film.
Cleaning before repair?
It is usual to inspect film and sometimes to carry out repairs to film
before cleaning prior to printing and in the case of negatives this may always
be the best policy. However old prints and some old well-used newsreel
negatives are so dirty that cleaning may be needed before any work commences to
avoid spreading the dirt or the dirt and grime creating additional scratches
and abrasions. The simply process of handling a dirty roll with white gloves
will soon demonstrate this problem. In any event, all film should be cleaned
after repair and immediately before printing.
There are many ways to clean film and some are more appropriate than others
are for archive film. Processes that use rotating buffers are rarely used as
they risk damage to insecure splices and torn perforations.
Essential procedures before cleaning
- Testing
The first procedure before any cleaning is carried out is to take a white
cloth with a little 1:1:1 Trichloroethane on it and wipe about 30 cm of
the film gently about three times and look at the dirt removed on the
cloth. If the dirt is dark and obvious, cleaning must be done in a
cleaning system allocated to dirty film. It can then be cleaned a second time in a "clean"
machine [unless a clean band solvent cleaner is used, see below]. This is
particularly essential on solvent cleaners in laboratories handling new
negative film, which will be contaminated by the dirt taken of really
dirty archive film. All cleaning machines have filtration but this is not
able to remove grease and oils and a "reclamation" process will
be needed to clean up the solvent before it can be used for fresh film.
The best practice is to keep a cleaning machine especially for the first
clean of archive film.
- Inspection
After the first wipe of solvent the film should be inspected by a hand
lens on both surfaces to see if the cleaning is effective. If it is not
and a lot of dirt remains, solvent cleaning may not be the answer.
- Lacquers and coatings
Some print films were [and some still are] coated with a protective
layer of varnish-like lacquer to protect them from scratching. If a film
is coated it can usually be detected on either side under a hand lens
either from the edges where the coating appears to chip away or from fine
drying marks or patterns that make the surface appear irregular or with a
"painted" appearance. Some films were coated on the emulsion
side only and others on both sides. There are two types of coating.
Solvent soluble coatings. These can be dissolved in isopropyl alcohol or
by normal 1:1:1 Trichloroethane cleaning fluid. These lacquers were
applied from the mid 1930's on and were very common on early 1950's colour
film. They could be scratched but if a scratch occurred it often did not
extend down to the emulsion. The lacquer could be removed with a solvent
[thus removing the scratch!] and the lacquer reapplied. Some of these
coatings come off easily and others may need several solvent cleans. If
this type of coating is found it is always better to remove it. It is
usually pale yellow with age, and removing it will remove a proportion of
the scratches.
- Water cleaning
Water would be an alternative to solvents if the marks are water
soluble [and Photoguard prints wash well], but this is difficult to test
on the bench unless a piece of the film roll can be found with no image
value. A cloth moistened with a mild surfactant or wetting agent such as
Photoflo and water can be wiped across and the result inspected as before.
This piece of film rarely dries uniformly and should not be used. The
re-washing procedure used for emulsion scratch treatment is also a very
effective cleaner.
- If the dust and dirt is loose
and will wipe off at a touch, an adhesive roller cleaner may be adequate,
but this is extremely unlikely in the case of archive film.
- Magnetic tracks should
be tested for cleaning, as some solvents will remove the magnetic coating.
A cloth with cleaning fluid should be used on an unimportant part of the
film, if a brown colouring appears on the cloth, no further attempt should
be made to clean the magnetic track with that solvent.
- The cleaning operation might
be the most hazardous part of the duplication process in some
laboratories, so it is important that the film is properly repaired prior
to cleaning if this is practical. Splices must be secure and any broken
perforations must be repaired or smoothed so as not to catch on any part
of the cleaning equipment.
- An even, firm rewind is
needed for test cleaning as for any other use of a film. The edges of the
film should be level.
- Sufficient length of
protective leader should be added to the front and end of each reel and
the leader should contain sufficient information for the reel to be
identified while out of its can. This would normally be the title, the
reel number, a description of the material and any identifying number such
as the location number or other ID number.
Once these procedures have been carried out, a decision on the method of
cleaning can be made.