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A. 2. Markings Produced Previous to Development caused by Condensation of Water Vapor from Humid Atmospheres.
Film is often subjected to humid conditions with resulting absorption of water vapor. If the film is suddenly transferred from a warm atmosphere to a cold atmosphere, condensation occurs on the surface of the film and tiny droplets of moisture are formed which may produce markings on the developed film.
Experimental Procedure. The tests were divided into three groups: (1) Humidification at room temperature, (2) Humidification at tropical temperatures (100° — 110°F.), and (3) Sudden changes from low temperatures to tropical temperatures and vice versa. For the experiments, special humidors were constructed, consisting of two motion picture film cans (200 foot capacity) soldered bottom to bottom. Holes were then punched in the separating wall and just before starting the test, a moist felt pad (l'Xl') was placed in the lower half of the humidor. The film in two or four foot lengths, loosely coiled was placed in the upper chamber for the test and the cover was then doubly sealed with adhesive.
The film was exposed so as to produce a density of approximately 0.8 after development.
Factors Influencing Nature of Humidity Markings
1. Effect of Nature of Emulsion. Several new markings were observed under varying conditions of humidification and refrigeration with all the emulsions examined. The markings were found to be due, however, to physical conditions to which the film was subjected rather than any inherent chemical nature of the emulsion.
2. Effect of Order of Exposing. In general the spots were more predominant on film which was exposed before humidification than on film exposed after humidification.
3. Effect of Time and Temperature of Humidification. Very few spots were observed on film humidified for one week at room temperature, but at tropical temperatures the number of markings was considerably increased, although only two distinctly different types were observed.
In general the intensity of the markings increased with time of humidification, reaching a limit after a certain time depending on the temperature.
4. Effect of Sudden Change of Temperature. When the film was subjected to sudden changes of temperature, from hot to cold or cold to hot, several types of spots were produced, but these with two exceptions were all similar in character to the spots caused by drops of water described above. The exceptions noted will be discussed later.
To summarize: No fundamental rule can be given relative to the chance of one or more kinds of spots appearing as the result of the order of exposure under the conditions outlined in Sections A.l. or A. 2. but in general all types of moisture markings are slightly more
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