To make lantern slides by direct contact printing is not a hard thing to do at all, and all the equipment you need to make them besides the chemicals is a printing frame. Put a sheet of clean glass in it and lay your negative on it with the film side up.
Now lay the lantern slide plate[62] with the film side down on the negative just as though you were going to make a print, but you must make it in your dark room, using a white light to expose it of course, for it is just as sensitive as a dry plate or a film. When you expose it hold the printing frame about 12 inches away from the light.
[62] Lantern slide plates can be bought at any photographic supply house.
A lantern slide plate is developed, fixed and washed exactly like a dry plate but to get the best results you should use the kind of developer called for in the directions that come with the plates.
When you have the lantern slide made, place a sheet of clear glass of the same size—called the cover-glass—on the film side of it and bind the edges with passepartout binding, that is a strip of paper gummed on one side. It is then ready for use.
How to Make Radium Photographs.
—You can make radium photographs, or skiagraphs as they are called, with any one of a number of radioactive substances and at a very small outlay.
The four most important radioactive substances, if we except radium itself, are black uranium oxide, pitchblende, thorium nitrate and uranium nitrate. You can buy any one of these substances in a glass stoppered bottle for $1.00 or the set of four for $3.50.[63]
[63] The L. E. Knott Apparatus Co., Boston, carries these radioactive substances in stock.
While the radioactivity of these substances is low it is sufficient to make a shadow-picture—and this is all that an X-ray picture is—of a coin or other small object if it is laid on top of a dry plate sealed in a black paper envelope, which is opaque to the light.