[Illustration: FIG. 14.--CIGARETTE TUBE FOR MAGIC PHOTOGRAPHS.]
Take an ordinary silver print and fix it without toning. Thoroughly
well wash it to remove all traces of the fixing solution and then
immerse it in a saturated solution of bichloride of mercury, when the
image will disappear. The bichloride of mercury changes the photograph
into white chloride of silver and chloride of mercury which is also
white. The image when on white paper is thus rendered invisible.
Next soak some strong bibulous paper in a saturated solution of sodium
hyposulphite, and, when dry, paste a piece of the paper to the back of
the invisible print with a little starch paste, attaching it by the
edges only. Of course the image can also be made to appear by soaking
the invisible print, without the bibulous paper attached, in a
solution of sodium sulphite, hypo, or water with a little ammonia
added.
[Illustration: FIG. 15.--DEVELOPING THE IMAGE.]
Magic photographs made in the manner above described can also be
developed by smoke. A novelty, introduced in Paris some time ago,
consisted of a cigarette or cigar holder, shown in Fig. 14, containing
in its stem a little chamber for the insertion of a small piece of
apparently plain paper, but in reality an invisible photograph
produced in the manner already described. The ammonia vapor in the
smoke passing through the chamber attacked the print and developed the
image. By blowing the smoke on the latent image it may be made to
appear, but the operation is rather tedious, and anyone with a little
ingenuity can easily construct a cigarette holder with an arrangement
to hold small pictures and allow the smoke to pass through.
The chamber of the cigarette or cigar holder must of course be
sufficiently large to allow of the print being inserted in such a
manner that the smoke can readily attack its surface, otherwise uneven
development of the image will take place.