Home Movies (1944)

• A wetting agent is a comparatively new chemical development which, when combined with developing and processing solutions, reduces surface tension of liquids on film, shortening developing and drying time. "wettim" mm AID TO PROCESSING By BOB AlTHOUGH photographic wetting agents, like vitamins, have been ballyhooed to the point where the confused amateur does not know what to believe, they nevertheless offer several clearcut advantages when properly used in the darkroom. Discounting the extravagant claims appearing on some of the labels and in some of the advertising, we may safely say that a good wetting agent — one properly designed for use with photographic processing solutions— has at least three legitimate uses in the processing and after-processing procedures. Before going into the uses of these compounds, perhaps we had better explain more or less what they are. A wetting agent is essentially a chemical which has the power of reducing the surface tension of a liquid so that it will not collect in droplets when poured over film, paper or any other non-absorbent material. To illustrate: if a spoonful of water is poured onto a dry tray, the liquid will not spread evenly over the surface of the metal but will, instead, collect in several small drops or one large patch with sharply defined edges. Now, if a few drops of wetting agent is added to the spoonful of water and it HURST is then spilled onto the tray, it will at once run out in all directions to make a thin even film of liquid. Because the wetting agent has lowered the surface tension of the water, it permits this spreading effect. The advantages of this action in connection with processing of movie films are readily discernable. Wetting agent in a developer makes for rapid, even wetting of the film so that the solution can commence working at once and uniformly on all portions of the film. Assuming the film is constantly agitated during processing, streaking as well as other faults of uneven development are thus automatically avoided. In addition, because the wetting agent causes quicker contact between all parts of the film and the solution, a more rapid job results. In the case of extremely fast working developers this effect is most valuable. With solutions of this type it is imperative that development commence simultaneously on every square millimeter of the film so that some portions need not be overdeveloped to allow other areas to reach full scale. Still another advantage of using a wetting agent in the developer has been noted: it seems to keep the solution clear HOME MOVIES FOR SEPTEMBER and free from suspended silver, thus producing cleaner negatives free from speckle. Moreover, this effect results in a longer useful life for the developer. In the stop bath and in the fixer, wetting agent again has a tendency to increase the speed of these operations, although not to such a degree as in the developer, for the film is already softened and somewhat absorbent. Nevertheless, certain obvious benefits accrue from this increase in speed when it is necessary to get the processing job done in a hurry. It is when wetting agent is used in the final rinse, however, that its chief advantage becomes most apparent. Because of this reduction of the surface tension of the water, films dry in onehalf the normal time without the necessity of resorting to infra-red bulbs or any other form of heat. Instead of collecting in droplets which are slow to dry and apt to leave spots, the water drains off readily leaving only a very thin layer of liquid which more readily evaporates into the air. Naturally, drying can thus take place at a much quicker rate. When used as a final rinse, a small amount (manufacturer's directions as noted on the labels should be followed) of wetting agent is diluted in a water bath and the film, after washing has been completed, is immersed in this tray for 2 or 3 minutes so that the material can penetrate thoroughly. Then it is hung up to dry in the usual manner, but omitting the usual swabbing operation to remove surface water. The avoidance of this wiping is, of course, advantageous as it prevents dangerous scratching or tearing of the softened film. As an additive to a tinting bath for cine films, wetting agent produces a much more even distribution of the coloring material. The decreased surface tension of the tinting solution permits it to cover all the desired parts of the film smoothly and rapidly. This is quite important when attempting to produce uniform pastel shades. In connection with toning, however, wetting agent should not be used as it is antagonistic to some of the materials in the toner itself. When toning, though, it is not so difficult to get an even distribution of color and thus wetting agent is really not necessary. Photo dealers have available a number of efficient wetting agents including Aerosol, Wondrop, Edwal Kwik-Wet, etc. All are low in cost and all have been proven efficacious for photographic use. Here, indeed, is a chemical aid that rightly belongs in even home processor's darkroom. Applied according to manufacturer's directions, it will improve and speed up home movie film processing and tinting, and the developing of positive titles, it it it 366