The sciopticon manual, explaining lantern projection in general, and the sciopticon apparatus in paricular (1877)

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64 CCIOPTICON MANUAL. the solution by allowing a plate coated with excited col- lodion to remain in it over night. Filter. Developing Solution. —Make a saturated solution of ammonia, sulphate of iron (in water); filter. To every ounce of this solution add glacial acetic acid, 1 drachm. This can be used as a stock solution, and will keep an indefinite length of time in good condition. Crystals will form in the stock-bottle, after standing some hours, but that is of no consequence, as the strength of the solution is correct. In developing a plate, use 5 drachms of water to 2 drachms of ammonio-sulphate of iron from the stock- bottle. During hot weather use ice-water to retard the action of the developer. Fixing Solution. —Cyanide of potassium or hyposul- phite of soda; either will answer, but the action of cyanide appears to make a somewhat brighter picture. These solutions being carefully prepared, the picture accurately focused, the negative (collodion side towards the lens) covered with a dark cloth, prepare the plate in the dark-room in the usual manner, place it in the dark-holder, in the position of the ground-glass, draw the slide (the lens is always uncovered), remove the cloth from the negative for a few seconds. The expo- sure will then be made. Cover the negative, shut the slide, and remove to the dark-room for development. The picture should appear slowly; not flash out upon the first application of the iron solution. Over-expos- ure, as well as over-development, are both fatal to trans- parencies. No trace of fog should be visible. From five to fifteen seconds will be found sufficient, on a bright day, with a negative of ordinary strength, and the chomicals in good order. The Negative —Must be sharp, of good printing densi-