THE DEVELOPING OPERATION.
The operator takes a couple of plates from the box and, giving them a tap on the bench to dislodge any dust that may have settled on them, places them, film side up, in the 10 in. by 8 in. dish. The film is easily recognised by its dull, creamy ap pearance, the glass side being bright and shiny. Four ounces of developer are then measured out from the glass jug, a 10-oz.
measure being used for the purpose, and poured with one sweep over the plates. The dish must be rocked at the same moment, so that the solution immediately covers both the plates. If this is done quickly and carefully, there will be no chance of the formation of air-bubbles on the film, or of part of the plate being left dry after the rest has commenced develop ing. The dish must now be gently rocked so that the solution flows regularly and evenly over the surface of the emulsion. An automatic rocker is a great conveni ence, enabling several dishes to be rocked at the same time, or left unattended. A typical pattern is shown by Fig. 185. Some workers prefer to allow the dish to stand, but this is almost certain to result in flat, lifeless negatives, lacking in brilli ancy. After a few seconds, the high lights will begin to appear as dark patches on the film, if the exposure has been correct ; these are soon followed by the minor lights, the half-tones, and last of all by the detail in the shadows. The plate, how
ever, must not be taken out directly it apears to be dark enough, since it will lose a good deal of strength in fixing. Develop ment must be continued until the negative is nearly opaque, and the shadow portion is just beginning to veil, This is judged by holding the negative up in front of the lamp (see Fig. 186). The light must be kept at a regular height, and the negative examined at a uniform distance from the lamp, or the results will be deceptive. The negative is then removed from the dish, rinsed lightly under the tap, and placed in a washing tank while the remaining nega tives are developed. It is hardly likely that any two negatives will be finished at exactly the same moment ; they are examined separately, and every time a plate is removed from the developer a fresh one is inserted from the box. When two plates have been developed, the solu tion is poured off and replaced by another 4 oz. of newly mixed developer from the jug.