minutes, depending upon the thickness of the film. As soon as it is dry the print is ready for use.
As already mentioned, the negative from which the metal print is made requires that the lines be perfectly sharp and opaque, and the spaces between perfectly transparent. Ordinary dry plates are too rapid, a rather slow plate being required. Wratten Process Plates give excellent results, and the following is a good developer to use with them:
| Glycin | 15 grammes | 1 oz. |
| Sulphite of Soda | 40 ,, | 2½ ,, |
| Carbonate of Potash | 80 ,, | 5 ,, |
| Water | 1000 c.c. | 60 ,, |
This developer should be used for 6 minutes at a temperature of 50° F., 31/2 minutes at 65°, and 13/4 minutes at 80°. It is best only used once. If an intensifier is required, the following formula will be found to give satisfactory results:
| Bichloride of Mercury | 1 oz. | 60 grammes. |
| Hot Water | 16 ,, | 1000 c.c. |
Allow to cool, completely pour off from any crystals, and add:
| Hydrochloric Acid | 30 minims | 4 c.c. |
Allow negative to bleach thoroughly, wash well in water, and blacken in 10 per cent ammonia .880, or 5 per cent sodium sulphide.
In preparing the negatives and metal prints the following points should be observed:
A good negative should have the lines perfectly sharp and opaque; there should be no "fluff" between the lines even when they are close together.