OREENLAW'S PROCESS.—A modification of the old calotype paper negative process. It is thus described : Thin negative paper is first selected, quite free from holes and of equal thickness. Then make up a solution of Potassium iodide ',boo grains Potassium bromide 300 grains Distilled water 40 ounces Then add enough pure iodine to give the solution a dark claret color. Filter. In a room lighted with yellow light, place as many sheets as required into this solution, care being taken against the formation of air bubbles. Allow the paper to remain in it for about an hour. Then turn the lot upside down and hang the sheets up to dry. The paper thus prepared will keep any length of time. To sensitize prepare : Silver nitrate 21 ounces Glacial acetic acid 21 ounces Distilled water 40 ounces Float a sheet of the iodized paper, smooth side downward, upon this until the purple color of the paper is turned to yellow (silver iodide).
After it has been allowed to rest for about a minute, remove it and immerse in distilled water. Next place it between two sheets of clear blotting paper and remove all superfluous solution, and hang up to dry. When perfectly dry, the paper may be exposed in the camera in the ordinary manner. Prepare : Gallic acid zoo grains Spirit of camphor t drachm Distilled water 40 ounces and, previous to development, add to every 5 ounces of the solution : Silver nitrate 3o grains. Glacial acetic acid 4 drachm Distilled water t ounce Pour quickly into a shallow dish, and float the picture side of the paper upon it. The image will be slightly visible, so no difficulty will be experienced in detecting the exposed side. Watch
carefully until the image is visible on the back, and continue the development until, in holding up a corner, where the sky of the picture is, before the light, you cannot see the finger if moved about between the light and the paper. If the image be insufficiently developed before the silver gallate decomposes, it is under-exposed. As soon as the silver gallate is decomposed it ceases to develop.
A more convenient method of developing is by brushing the solution over the paper previously wetted with water.
After development the negative is well washed, and fixed by placing it in a solution of sodium hyposulphite, i% ounces to z pint of water, until all yellow silver iodide disappears. After this it is well washed in many changes of water, and a clear, fine, and dense negative is the result.
GREEN PAPER.—An albumenized paper can be obtained of a slight greenish tint. It is often preferred for printing landscape negatives.
GREEN PICTURES.—Obtained by floating paper on a 6o-grain solution of uranium nitrate, and exposing for about ten minutes under a negative. Hardly any effect is visible until the paper is washed and brushed over with a weak solution of potassium ferrid-cyanide, which will develop a red image. Whilst still moist it is immersed in a solution of sesquichloride of iron ( io grains to the ounce), and the tone will soon change to a bright green.
GREEN SPOTS.—These sometimes make their appearance in prints, and are due to the presence of small particles of inorganic matter in the paper.
GREEN VITRIOL.—(See Ferrous Sulphate.)