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of the following causes : (a) excess water remaining on the emulsion side of the film, (as illustrated in Figs. 11, 12, 13, and 14) or (b) excess water left on the base side of the film, (as shown in Fig. 15). In the latter case the local areas on the emulsion side directly opposite the moisture spots on the base side are cooler than the surrounding film resulting in a selective drying action, as noted in a. recent article by one of the authors.1 The severity of the markings produced by either of the above causes is directly dependent on the temperature and the humidity conditions and on the time of drying.
11. Spots with Dark Narrow Outlines. This marking is distinguished by a dark narrow band which constitutes the edge of the spot. All the area within this band, is of the same density as the rest of the film. It is caused by large droplets of water remaining on the emulsion side.
12. Dark Gray Spots with Small White Centers. When large drops of water are accidentally left on film which is subjected to rapid drying at high temperatures (90°-120°F.) spots are produced whose general density is considerably darker than the surrounding film. The point in the spot where the last water evaporates appears as a tiny white spot. In some cases, a narrow white halo may be found just inside the outer edge of the spot.
13. Hazy White Spots. Occasionally on film which has been developed in solutions at temperatures around 80° F. or over, when the gelatine is in a swollen condition, small vaguely defined white or gray spots are found, especially if the film is dried rapidly at high temperatures (120°F.) even when all superfluous moisture is removed. The markings resemble No. 1, except that the outlines are usually less clearly defined.
14 Streaks. Sometimes streaks remain on the film during drying which cause long string-like gray marks of slightty heavier density than the rest of the film. Variations are found where the edges are dark and the side of the streak is light gray. This marking occurs on film dried either at room or tropical temperatures.
15. Spots with Gray Halos. The most common marking found as a result of the presence of water on the base side of film is a spot with a hazily defined edge or halo of much lighter density than the center, where the density is nearly the same as the remainder of the film. On film dried at room temperature, this marking is just discernible but at higher drying temperatures the spots are greatly accentuated. Other varieties are (a) gray streaks along the edge of the film just inside the perforations as shown also in Fig. 15 and (b) small round light gray spots of even density. All spots caused by water on the base side are less distinct than those caused by water on the emulsion side.
Theoretical Discussion
From an examination of the various markings produced by moisture, it is seen that there are three essentially different types; namely, (1) black spots or local areas of greater density than the
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