Page:Popular Science Monthly Volume 89.djvu/786

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��Popular Science Mo)ithly

���as an example; even oil, gas or a match, held a foot from the frame, may be used instead. The exposure would then have to be determined by experi-

. , y . ,,- ment, of course.

'I "* I " 1^ r When the ex- posure has been made, the plate is taken from the frame and placed Detail of in a tra\- contain- support i,^g ^\^^ developer.

The writer favors the popular M.Q., sold in tubes and merely dissolved in water. In about thirty seconds the de- tails of the image will come up under the action of the developer, and in possibly a minute and a half, the development will be complete. This is determined when the entire image is plainly visible, though hazy, on the reverse side of the plate. Another test is to look for the details in the highlights; when they are visible, the plate is developed. The tray should be rocked continually- throughout de- velopment.

The next step is to rinse the plate in clear water and immerse it quickly in a bath of hypo, which may be purchased in

���Safe base sV-' dross feefi'/i/gh-'

3 Coils each containing 5 ft. of No. 22 re- sistance wire. Wind 48 turns on Jin. rod

���Fig. If). Details of a small rheostat. In the slate base nine brass pillars are mounted

small packages readx- lo be dissolved in water. When nt) more of the milky white- ness can be <kle(ted on th<' ])late when

��//ofo/fcircu// ^'6- 17- viewed from the back.

Diagram j^ g,^,,^,,^, |,^. [^.fj -^^

of thewir- , ,

from ^he hypo ten mmutes

nearby longer, and then taken

lamp-soc- out and washed under


��ket to the rheostat



��running water for a half hour. All of these operations must, of course, be performed under the orange light. The trick which is perhaps the most im- portant of all in the making of a slide has been left until the last, where it will be noted and remem- bered. When the slide plate is placed in the printing frame ready for the exposure, a piece of black paper should be placed over the back of it before the cover of the frame is clamped in place. This is to prevent a disagreeable foggy flatness from spread- ing all over the slide-plate, which will happen if the reflected light from the white backing of the printing frame strikes through the glass. The author has made hundreds of slides without the slightest difficulty since he discovered this little stunt. Prior to that time he had foimd it impossible to secure a brilliant slide from any but the snappiest of negatives.

A concluding word of caution is to avoid touching the emulsion side of the slide plate at any stage of the operations. The emulsion, when wet, is soft and easily injured and, when dry, the oil from the fingers will leave a mark. While the slide is drying, it should be |)rolcrled from dust and dirt, preferably by [)lacing it in a clean, dry i)lace. \ mat or mask and a cover-glass boimd on the slide with passe partout binding complete the work.


��A Substitute Blow Torch for Soldering Joints N easily impro\iscil blow torch lor soldering joints in wires is ni.ule as follows: Take a \'i-\n. tube, and till it with cotton waste or with old cloth satu- rated with gasoline. Cut a notch in a piece of ]/\-\n. loom, insert it into one end of the tube, and light the waste. Blowing through the loom makes a hot flame.

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