[FACTS WORTH MENTIONING.]
FACTS WORTH KNOWING.
The Poisonous Effects of cyanide of potassium upon sores, may be obviated by immediately applying some of the positive developing solution, described at [page 62]. By this means much annoyance may be avoided to persons afflicted with chapped or sore hands.
Bending Glass Rods or tubes can be easily done by subjecting them to the blaze of a spirit lamp—the same as that used for gilding the daguerreotype. First hold the rod just above the blaze, then gradually allow it to descend into it, imparting to the rod a rotatory motion with the finger and thumb: this will soon cause a softening of the glass, when it may be bent to any desired shape. If the ends are to be bent to form hooks, another small piece of glass, or any warm metal, may be placed upon the end, in the blaze of the lamp, and as soon as thoroughly softened, it can be pressed or bent to form the hook. By filing around a glass tube or rod, it may be easily and safely broken at the desired point, by giving it a sudden jerk between both hands, holding it close to the encircled part.
Cementing Glass may be readily accomplished by placing the two ends together in the blaze of the lamp, and holding them there until they attain a sufficient degree of heat to slightly fuse: when cool, the ends will be found perfectly united.
The Background best adapted to positives is unbleached muslin, such, as is sold for sheeting, and can be found in almost any dry goods' store: it should be from two to three yards wide. A clouded appearance is given to the background by merely marking it with charcoal, forming streaks or "waves" resembling clouds. These come out black, or dark, in the positive, and give a variegated appearance. The roughness of the marking does not matter, since the background is generally a little out of the focus of the lenses. Trees and other designs may be represented in this matter.
Positive Collodion Pictures may be whitened by the use of bichloride of mercury, thirty grains to one ounce of water. After the picture has been developed, fixed and washed, by the process given in the preceding pages, the solution of bichloride of mercury may be poured over the surface of the image: it almost immediately presents a series of interesting changes in color. The surface at first blackens but for a few minutes, when it begins to get lighter, and gradually brightens to a pure white, inclining to a blue. It should then be thoroughly washed and dried, as usual.