The picture is faintly visible. If the negative was too thin, or if it be over-printed, the image develops badly or not at all. With under-printing the film washes right away.
Immediately after printing the stone or plate is coated with solution B, which is distributed as evenly as possible by rocking backwards and forwards. It is not necessary, however, to obtain even distribution with a whirler. The whole of the coated surface becomes deep violet.
(C.) THE DEVELOPMENT.
When solution B has become completely dry, the stone is placed in a suitable vessel with pure water. After about five minutes the places not affected by light dissolve if the stone is rocked, and it is only necessary to go over the drawing with a pad of cotton wool to clean the same completely. The drawing now appears a deep violet on a bright ground. The development is continued without rubbing strongly with the pad—which might rub up the drawing—till all the details of the drawing appear clear and distinct. This especially applies to the details in the deep shadows.
(D.) FURTHER MANIPULATIONS.
When the stone or plate is correctly developed, which can be easily told, it should be well rinsed and again exposed to make the film adhere firmly. It should then be gummed and treated as previously described in the asphalt process. The “rubbing up” of the stone or plate is not necessary; it is better to roll up the drawing with an ink roller. Zinc plates for deep etching can be lightly etched, then dusted with fine asphalt of resin powder, heated and then further etched. {66}
R. J. Sachers, of Toronto, Canada, published a sensitive solution which has the following composition:—
| Distilled water | 150 | parts |
| Fish glue | 50 | parts |
| Ammonium bichromate | 2 | parts |
| Ammonia | 2 | parts |
| Chromic acid | 1 | part |
This solution is brown, not very transparent, with an olive green tinge, and must stand and settle at least twelve hours before it can be decanted, filtered, and used. The time of exposure is about—
| Direct sunlight | 2–5 | minutes |
| Diffused light | 12–15 | minutes |
| Electric arc light (3000 c.p., 50 cm.) | 30 | minutes |