High humidity combined with high temperature are conditions, which will
promote the growth of fungus and bacteria on the emulsion of film. However many
films are found to have been attacked by organisms that feed on the gelatine
substrate that are not stored in poor conditions. It is possible that they have
been in poor conditions in the past or that something about the film makes it
slightly different from other film and more attractive as a substrate. It is
not uncommon in newsreel
collections that have been housed together all their existence to find a short
period of material that is seriously effected by bacteria or fungi. Both
nitrate and acetate films are affected but some colour films [probably because
their last process stage included formaldehyde, a very good fungicide] are
never affected.
The distinctions between fungi and bacteria are imprecise. It is usually possible to distinguish between the two under a microscope. The fungal hyphae can be seen as strands running over the surface or through the gelatine of the emulsion, whereas bacterial colonies appear circular or patchy under a hand lens but at higher magnification are more or less amorphous as the individual cells are not obviously arranged in chains.
There have been some interesting studies on gelatine feeding organisms but the concern of this publication is to discuss how the effects can be minimised visually and prevented from continuing to grow.
It has been noticed that tinted films are frequently affected by fungal growth. Interestingly, it also known that acid solutions of some of the dyes used for tinting in a modern laboratory [Soho Images] has been affected by a prolific surface growth of fungi, and presumably dyes are a good substrate.
In many cases, it seems likely that the growth of the organism stops without any influence from man, as many examples do not increase in size and effect if they are kept and observed. Presumably, the conditions needed have ceased to exist and the organism is either dormant or dead.
How to Detect fungi & bacteria