Three-Dimensional Photography - Principles of Stereoscopy

308 THREE-DIMENSIONAL PHOTOGRAPHY

been properly hardened you can wash two or three hours without

danger, but one-half to one hour in some device which thoroughly

agitates the films or prints, or in a rack which keeps them posi-

tively separated, is sufficient. We have stereo negatives on hand

which were made in 1918 and were fixed and washed this way.

They are as printable as the day they were made.

Swab the negatives off after washing, squeegee to remove sur-

plus water and dry in a place where drying occupies from one to

three hours, neither too rapidly nor too slowly.

As soon as they are dry, cut the negatives apart, transpose them

and place in individual protective envelopes. Negatives left lying

around collect dust and dust makes scratches even upon a proc-

essed negative. If a negative is worth making it is worth protecting

-and a scratched stereo negative might as well be destroyed.

THE STEREO POSITIVE
For almost a century, stereo negatives have been made princi-
pally upon glass, and printed upon either paper or Glass. The
recent revival of stereo is only a few years old, and is based upon
the use of 35mm reversible color film. The physical differences
have resulted in confusion and in the inevitable attempt to modify
old processes by modern techniques.
Thus today we have adherents of glass for both phases, of film
negatives and glass positives, of film negatives and positives, of
glass negatives with paper positives and film negatives with paper
positives. Only in the modern phase do we find a definitely stand-
ard procedure, that of 35mm color film.
It is difficult to obtain glass sensitive material, and only a few
dealers carry it. The general trend is toward the use of film in
the camera, paper for prints and film for transparencies. It has
been our experience, however, that glass diapositive plates make
possible a quality which we have not been able to duplicate with
sheet film. However, that is a minor matter as the difference is
slight.
One thing is important. There is nothing available in the
35mm field to compare with the automatic cabinet viewer or
“classifier.” The result is that many users have adapted the old
cabinets to modern mounts. A viewer which makes use of side