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Topic: John Pytlak: Kodak discovery on VS?
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Leo Enticknap
Film God
Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000
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posted 08-30-2001 06:23 AM
The original 'Broadway Melody of 1936' negative would almost certainly have been nitrate, which is not affected by vinegar syndrome (because the cellulose is dissolved in nitric, rather than acetic acid). Unless the surviving element is a diacetate intermediate, I can't see how any treatment designed to address vinegar syndrome would help it.Fine-grain interpositives, which were contact printed onto acetate butyrate or acetate propionate stock direct from the camera negative, were sometimes made as so-called 'insurance prints' due to the reduced risk from fire. Some insurance companies insisted that these be struck and stored in a security vault as a condition of underwriting a production. Acetate (safety) film was not used on any significant scale by the movie industry until the launch of 'high-acetyl' cellulose triacetate in 1948 because it was far more brittle, fragile and prone to short-term shrinkage than nitrate was. However, it was OK for just printing once or twice, hence its use for insurance safety copies. In fact, the term 'insurance PRINT' is quite misleading, because they are in fact many generations closer to the original negative than any release print would be. Quite a few films have been saved that way. For example, when a nitrate vault burnt down at a small lab in South London specialising in archival work in 1992, the camera negatives of several well-known Ealing comedies, which were being printed up for a national re-release, were lost. New preservation masters were made from the insurance prints, which the National Film and Television Archive had kept in a separate location.
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 09-04-2001 02:26 PM
Leo said: "The original 'Broadway Melody of 1936' negative would almost certainly have been nitrate, which is not affected by vinegar syndrome (because the cellulose is dissolved in nitric, rather than acetic acid). Unless the surviving element is a diacetate intermediate, I can't see how any treatment designed to address vinegar syndrome would help it."Although cellulose nitrate and cellulose triacetate are different polymers, the hydrolysis reaction that causes degradation of the base is similar, releasing acid vapors and moisture. In a sealed container, Molecular Sieves adsorb the moisture and acids released, and so will slow the degradation of either type of film:
http://www.kodak.com/country/US/en/motion/support/technical/molecular.shtml
http://www.kodak.com/country/US/en/motion/support/technical/vinegar.shtml
http://www.kodak.com/country/US/en/motion/hse/safeHandle.shtml
http://www.kodak.com/country/US/en/motion/hse/mole.shtml ------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion
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