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Re: CF3000

--- Forwarded mail from Zwaneveld Eddy <E.HA.ZWANEVELD at NFB-ONF.CA>


Our CF3000 MkVI has been online and in daily use for 6 months. Other than 
that it has to run at the lowest speed, about 50% of the speed we used to 
run at with CF-2 (tricholoethane) and which is very costly and hardly 
available anymore, we are satisfied with it. We are also recovering our Perc 
and that works well.

It is therefore quite academical as to whether one prefers trichloroethane. 
 However, it is preferable from the health and safety perspective. 
Trichloroethane, also known as Methyl Chloroform has a Permissible Exposure 
Level (PEL) for an 8-hour Time Weighted Average (TWA) of 350 parts per 
million (ppm). Overexposure by inhalation could irritate the eyes, skin 
contact can also be irritating and drying. It can have an effect on the 
central nervous system (CNS) and cardiovascular system (CVS) and respiratory 
tract, but it is considered one of the least toxic of the liquid chlorinated 
hydrocarbons. It is not listed as a carcinogen. It contributes to the 
depletion of the ozone layer, hence manufacturers and users are committed to 
replace it with another cleaning agent, hence increased taxes and limited 
availability. It has a boiling point of 165 degrees F ( 75 degrees C).

Perchloroethylene, also referred to as Perc, or tetrachloroethylene, which 
is used by dry cleaners and textile processors, has been used for years in 
wetgate immersion printing, because its refractive index of 1.50534 at 68 
degrees F (20 degrees C) for light,  matches that of the film, it 
temporarily eliminates the reproducibility of filmbase scratches (while the 
film remains wet and the scratch filled with the liquid). It has a boiling 
point of 250 degrees F (121.2 degrees C), which explains it much slower 
drying time.

Its Permissible exposure Level (PEL) for an 8-hour Time Weighted Average 
(TWA) of only 25 ppm, is much lower than of Trichloroethane.  The US 
National Institute for Occupational Health and Safety considers it a 
Carcinogen, which is based on animal tests, human data is not yet available 
in sufficient quantity, however the animal evidence make it justifyable to 
assume it to be carcinogenic to humans as well. Percholoethylene is stored 
in the fatty tissue and slowly metabolized with the loss of chlorine. It has 
its greatest impact on the central nervous system (CNS), and its symptoms 
range from lightheadedness and slight inebriation to unconsciousness. Liver 
damage is possible after severe acute or minor long-term exposure.

This means that doors to the cleaning equipment must be kept closed until 
air saturated with perchloethylene (or trichloroethane) has been evacuated. 
This depends on the efficiency of the local exhaust. It can be measured with 
a Draeger Air Sampling pump, using a glass indicator test tube for perc or 
tricholoethane. Exhaust systems have been known to fail, overexposing 
employees, so ongoing vigilance is required.

For these reasons, perchloroethylene as a film or (dry)cleaning agent is 
transitional and temporary, until a suitable agent is found which meets all 
the film cleaning and human interface criteria, without causing the users to 
lose their shirts.

Best regards,

Ed H. Zwaneveld
Technical R&D
National Film Board of Canada
e-mail: e.ha.zwaneveld at nfb-onf.ca
tel: 1-514-283-9143

--- End of forwarded message from Zwaneveld Eddy <E.HA.ZWANEVELD at NFB-ONF.CA>

Rob Lingelbach          |  2660 Hollyridge Dr., Los Angeles, CA 90068
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