Degradation of Historic Cellulose Triacetate Cinematographic Film: Influence of Various Film Parameters and Prediction of Archival Life

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Abstract
The natural and artificial degradation of cellulose triacetate based cinematographic film has been studied by moisture regain and viscometry. The influence of the emulsion, plasticizer and nature of the storage container are investigated as well as the effect of plasticizer loss. A cross-sectional analysis on reels of films indicates that older films are more severely degraded due to a higher moisture content. Under both natural and artificial ageing degradation is greater where the film is in contact with the environment with the emulsion layer and plasticizer offering some degree of protection to the acetate base. Plasticizer loss is accelerated under humid-acid conditions with increasing temperature but impaired by the emulsion layer acting as a diffusion barrier. The degradation. of reels of film are also examined in glass, high density polyethylene, aluminium and standard tin-plated iron containers at 50% relative humidity (RH) at different temperatures. The extent of degradation is measured by the time for the film to lose 10% of its viscosity and the data plotted against the reciprocal temperature using the Arrhenius expression. Extrapolation of the data to room temperature (21°C) gave archival lives for the film of 110, 60, 50 and 35 years respectively at 50% RH conditions. The importance of these results in relation to the practical archival storage conditions of cinematographic film and earlier experimental predictions are discussed.

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