When abroad making views it is sometimes necessary to change the plates in the holders; for this purpose carry with you a ruby glass gas burner chimney, which is a plain cylinder of ruby glass, about one and a half inches in diameter and six to eight inches long. Light a short piece of candle and set the chimney over it; this in any small dark closet will give plenty of p174 light for the purpose, and indeed might do to develop by at a pinch.
LANTERN ARRANGED FOR DEVELOPING, AND AFTER FIXING, EXAMINING NEGATIVES BY OPAL LIGHT.
FERROUS OXALATE DEVELOPMENT OF DRY PLATES. (ROCHE.)
First make two stock solutions as follows:
No. 1. A saturated solution of oxalate of potash (a pint or quart) and test with blue litmus paper. If it does not show an acid reaction dissolve a little oxalic acid in water and add enough to the solution to cause the blue test paper to turn red.
This solution should be filtered for use.
No. 2. Make a saturated solution of pure sulphate of iron, and to one quart add three or five drops of sulphuric acid, to prevent oxidation, and filter.
Now, to develop a 5x8 plate, take three ounces of No. 1 and to this add one quarter of a dram of bromide of potassium solution (which is water one ounce, bromide of potassium twelve grains), then add half an ounce of No. 2; this forms the developer. p175
Then transfer the plate to a developing disk, and pour over it the developer. If the picture comes out gradually and develops sufficiently, it is good so far, but if from under-exposure the details hang back and refuse to develop further, then add two drams, or half an ounce, more of No. 2, which will bring out the picture with full details, unless greatly under-exposed.