192. I have kept silver stains from my hands for the past six or seven years by the use of pumice - stone. Take a piece the size of an egg, and file it smooth on all sides. When through the day's work, rub the hands with the stone under the tap, and away go the stains. I got poisoned with cyanide some years ago, which induced me to try the above, and, until I find something better, I shall stick to the pumice-stone rather than have the silver stick to me. - Well G.Singhi.
Sulphate of soda and chloride of lime, equal parts each. Add just enough water to make a rather thick solution. When about to clean the hands, smear them well with the above. It will not act instantly, but in about five minutes every trace of silver will have disappeared. Wash well in clean water, and after drying the hands rub them over with a little glycerin, diluted one - half with rose - water. This will soften the skin, which the lime is apt to render harsh, and prevent chapping in cold weather. - F. C. Phillips.
198. Many persons are now using the alkaline development, and it is well to point out that if the ammoniacal vapors are allowed to mingle with the air of the laboratory they produce a fog on plates treated by the wet process and developed with the iron salt. To avoid this serious trouble, it is necessary to ventilate the laboratory after having used the alkaline development, otherwise there is a risk of losing the plates which are successively treated there. It is not only necessary to renew the air as much as possible, but to sprinkle a little acetic acid on the floor to absorb the ammoniacal vapors. - Unknown.
The ventilation that is necessary is certainly mora than that which would be accomplished by having two or three small openings for the admission and exit of air. Some system should be devised whereby a rapid and constant change of air in these little apartments can be certainly produced, and it never is a difficult thing to accomplish. A tallow candle, lighted and placed in a little flue, or a small kerosene-lamp, in such a position that it will cause a current to pass up through the flue, and out of the laboratory, and a few holes at the bottom, for the admission of air, make a constant and tolorably rapid current to pass through the room, and insure a rapid change of atmosphere; and, certainly, tallow candles and kerosene are sufficiently cheap. The ways of securing ventilation are simply numberless, and no photographer, with a little care of this sort in ventilating his rooms, need ever com-plain of the harmful effect of fumes and gases. By diluting them with atmospheric air in 10 living at a ripe old age, and life insurance companies consider photographers quite as good "risks" as any other class, but too much care cannot be given to the avoidance of unnecessary inhalation of the fumes arising from poisonous chemicals. Ventilation and a frequent airing of the dark-room will secure you from evil results in this direction. (See page 92.) 194. There are other defects, many of them, which annoy, but they can be largely avoided by regarding the following rules: Have your glass very clean; keep your bath well filtered and slightly acid; let your collodion be a good orange-yellow color; have your developer fresh and clean; see that there are no splits or cracks in your dark-room, by which white light is admitted; see that your cameras and plate-holders are in good condition and perfectly light - tight; never allow reflected light to enter your camera, but so screen your light that the direct rays will fall on the sitter, and leave your camera in the shade; never take out or develop your plate by too strong a light; if you use yellow glass to light your dark-room, coat a plate, and expose it for three or four minutes near the glass, and then develop it; if it fogs, put a yellow cambric curtain over your glass; keep your hands and everything about you perfectly clean.
194. "Closet speculations," as I will term them, are, perhaps, the most dangerous things which can be thrust forth on far-off and credulous readers. Of these we have ever and anon a surfeit. They are, of all things, most difficult to detect. No doubt many are given in good faith, but there is a good deal of "hap-hazard " to be gone through before we arrive at the realization of our hopes. One will tell you to a centigramme how much silver he dissolved in an equally certain quantity of alcohol; that it was heated, etc.; but he cannot for the life of him tell you, short of an almost unheard-of experiment (for an ordinary photographer), whether every atom of that silver nitrate was "got in." By the addition of certain bromides, chlorides, and iodides (one or more combined), he has obtained about that which was necessary to the successful working of his process. Luckily for photographers, the "chemistry of photography " is good-natured, and seems to admit of a "rule of thumb," but in order to appreciate this, we must always be on the lookout. - A. M. De Silva.
Little Things worth Looking after. - Keep the inside of your camera-box free from dust: I have heard bath solutions condemned when the fault was dust from the camera-box. Every time you shut your ground-glass, or put in the shield, draw the slide, or remove the shield, you start a current of air that will put any quantity of dust in motion if it is in the box. Keep your shield or dark-slide well greased. Be sure you wipe off all, only what goes well into the pores of the wood. It will not injure the working of any of your chemicals, will keep the shield in the best of order, and will make one shield last longer than two would without it. Lard or mutton tallow will do. - Frank Rowell..