In fact, this instrument might very easily be converted into a solar camera by fixing it in a window and adjusting a mirror outside that would reflect the sun's rays into the condenser within the box.
TO ENLARGE NEGATIVES BY THE REVERSING ACTION OF LIGHT.
Having coated a plate with the common negative collodion and excited it in the usual nitrate of silver negative bath, expose it to the light for about a second at the door of the dark room, wash it and then apply to the surface as a wash a solution of
| Iodide of potassium | 16 grains. |
| Bromide of potassium | 8 grains. |
| Water | 1 ounce. |
The plate is now ready for exposure in the enlarging camera; the lime or the magnesium light being sufficiently powerful for the purpose. On its removal from the camera the plate is washed, immersed for a brief period in the nitrate of silver bath, or otherwise treated with a solution of this salt, after which the image is developed by the ordinary developing solution p207 for wet plates. In this way is obtained an enlarged negative from a small one without the necessity of an intermediary transparency.
PRINTING WITHOUT SALTS OF SILVER, FROM THE "SILVER SUNBEAM."
The discovery that certain of the per salts of iron when exposed to light undergo decomposition and are reduced to proto salts, is attributed to Sir John Herschell. But we are indebted to Poitevin for numerous interesting developments in this department.
For instance, the per-chloride so exposed becomes reduced to the proto-chloride; or, as Von Monckhoven more appropriately remarks, to the state of oxy-chloride. For this purpose the sesqui-chloride must be quite neutral. The ammonia tartrate, potassa tartrate and the ammonia citrate of iron are much more sensitive to light than the sesqui-chloride, and the latter salt (ammonia citrate) most of all.
The image formed by means of these salts is much fainter than that with the chloride of silver; but it can be intensified by the application of other metallic salts.
The mode of operation consists in floating the paper on the solutions in question in the dark room, in allowing them to dry, and then exposing them afterward beneath a negative, as usual with paper prepared with chloride of silver.