The manufacture of dry plates has now reached such a state of
perfection that the purchaser may procure them of every grade of
sensitiveness, each of the several grades of a perfect uniformity
and all of them very free from imperfections and blemishes. And also
the prices have been so reduced of late that the incentive to
manufacture on the part of individuals for their own use is almost
entirely lacking. However, there may be found [p145] a certain
interest and fascination in preparing plates for one's own use,
which would prompt some to incur the outlay and trouble incidental
to such a course, and for those full instructions and formulæ may be
found in the first part of this book.
It will, however, be found, after due trial, that for work of
importance, and where certainty of results is desired, it will be
better to procure the plates of some maker of established
reputation, and of such a grade of sensitiveness as will be most
suitable for the work in hand.
Certain makers of dry plates use the Sensitometer to ascertain the
degree of rapidity of each and every emulsion produced in their
works. The ascertained degree of rapidity is indicated on each box
of plates by the Sensitometer number--the higher the number, the
more sensitive the plate. The highest numbers attained up to this
time are from 20 to 25, and these numbers would indicate a very high
degree of sensitiveness, such as render plates of 23 to 25 quite
suitable for work requiring the shortest possible, in fact,
instantaneous, exposures, such as bodies in motion across the plane
of focus. Views of still life are better made with plates of a
lesser degree of rapidity.
The handling of dry plates of such extreme rapidity requires great
care. The boxes should never be opened, even the outer wrappings
should not be removed, except in the darkened room and by such a
light as that produced by Carbutt's dry plate lantern or some
similar device. When plates are taken from the boxes for the purpose
of fitting the holders, they will be found to have one clear, smooth
and shining surface. This is the back of the plate and is clear [p146]
glass; the other surface is of the same color, but of a mat or
dead color, not reflecting so much light. This is the sensitive
surface, and before being placed in the holder or shield it should
be brushed with a soft, flat camel's hair blender, to remove any
dust that may be attached to the surface. This brush should be used
for no other purpose; and should be used without pressure, merely
touching the surface of the plate. The plate may then be put in the
plate carrier of the shield, with the sensitive surface outward, and
when the carrier is run into its place in the holder, the sensitive
surface is next the slide or door. It is of some importance that
attention should be given to this manipulation, as it not
unfrequently occurs that the wrong side of the plate is turned
outward and the image, when the plate is exposed, is made through
the glass and against the back of the film, and is reversed and thus
rendered worthless, even should a good impression have been secured.
The holders or shields for dry plates for out-door work are
always--except in the largest sizes--made double, each holder
containing two plates.
[Illustration: ANTHONY'S PATENT PERFECT DOUBLE DRY PLATE HOLDERS OR
SHIELDS.] [p147]
The diagram exhibits the plate holder, 3, with the plate carrier, 1,
partly drawn out; the slide or door corresponding to 2 is withdrawn
to show the interior of the holder, 3, and the spring that presses
the plate into focus, when pushed into the carrier, 1. This carrier
presents the same appearance on the other side and will hold two
plates. When filled with plates, it is pushed into its place in the
holder, 3, and the brass loops or fasteners, 4, are pressed down
flat, thus securely holding it in place. When the holder is put in
place at the back of the Camera the slide, 2, next the box, is
pulled out quickly and in a perfectly level position, so that the
spring shut-off may close instantly and permit no light to enter the
opening. The lens must be covered before the slide is pulled out.
The exposure is then made and the slide is returned to its place in
the same manner, carefully observing that one corner is not entered
first, but the end must be inserted into the groove squarely and
pushed quickly home. If another exposure is to be made immediately,
the holder is removed and the opposite side placed next the box, and
the same process is repeated, covering the lens, removing the slide,
make the exposure by removing the cover of the lens and replacing
it, then return the slide to its place. When a second exposure is
not made at once, with a pencil or in some other manner mark the
side that has been exposed, to prevent any mistake. When both plates
are exposed, return the holder to the carrying case and take the
next, if you carry more than one. Usually a half dozen holders are
carried, which gives command of one dozen plates, which should be
quite enough for one outing. [p148]
Having exposed the plates, the holders are returned to the carrying
case, and should not be removed therefrom until they are taken into
the dark room for development, when, by the aid of some safe light,
they may be removed from the holders, one at a time, and developed,
or all taken out and put into a negative box, to be ready for
development when convenient.