Evening star., 1950-06-04
Third of a SerieS.)
Y Alexander J. Wedderburn
Cvrotor Of Photography
The Smithsonian institution

Slides, whether you use film OF
glass plates, are processed just as
you would develop, fix and wash a
negative. The makers of slide
materials furnish processing
tables with the stock, recommend
ing certain developers and offer
ing other constructive suggestions
1t is advisable to follow them to
the letter in the processing Of your
slides.
For example, one manufacturer
provides two types of positive
films for slide making. One is for
use with fiat negatives and the
other is designed to handle both
normal and contrasty negatives.
If you have a preference for
plates. you will have the same
choice. And please use the de-
veloper suggested by the slide
material maker if you expect best
results. OF course, it is possible to
use other developers, but there is
little point in pitting your ideas
against the research laboratories
that have tried them all and ar
rived at the best answer.
Processing procedures will vary
according to your choice of ma
terial. A white bottom tray will
make it easy for you to observe
the progress Of development of
glass plates. Slide films are bet
ter handled in the same roll film
tank that you use to develop
negatives.
Divide According to Contrast.
No matter how great the pains
you take in exposing and develop
ing your negatives, you will find
that they are not all of an identi-
cal contrast. Therefore separate
into groups the negatives of fiat
or normal and contrasty appear
ance and print each group sep
arately on lengths of positive film
or in separate plate patches. Then
each length of film or batch of
plates can be developed to the de-
sired contrast. This is important
because you will want your slides
in a series to match as we'll as
possible.
The slide materials may be in
spected under a safe light rec
commended by the manufacturer
just as you inspect prints. AS in
the case of negatives, the image,
as it appears in the developing
solution, will not be identical in
resemblance to the image as it
looks after clearing. The relative
difference will become apparent
to you after a few tries, and if you
have had experience in develop
ing negatives this factor will pose
no problem at all. While the
slide is in the developer, keep your
eyes peeled for one of the two
signs that will indicate a faulty
exposure. If the image pops up
almost as soon as the slide hits
the solution you may conclude
that your exposure was too great.
If prolonged development fails to
give a satisfactory image, you
should make another slide at a
greater exposure.
Intensiflcation or reduction
might help out in these cases but
considering the wasted time, addi-
tional chemicals used, the low cost
Of the slide material, and the
natural desire for a perfect slide
you will be happier ins the long
run If you toss your failures in
the waste basket and try again.
Use Care in Handling.
After the developer, the slides
should be given the same care
that you give a priced print. Ten
to fifteen minutes in a hardener-
fixing bath should be followed by
thorough wash in running water
for at least 30 minutes. Then the
slides should be carefully wiped
free of scum or grit with a