/ . t
SCIOPTICON MANUAL. 69
The preservative must be fresh. Three ounces of this
mixture will prepare half a dozen 6$ x 8$ plates.
If the preservative is poured over the plate, apply
twice, working it well into the film ; throw the first dose
away, and use the second flowing for the first applica¬
tion to the next plate.
The plates must be carefully dried, either by natural
or by artificial heat; a hot-water bottle will be found
useful for that purpose should artificial heat be thought
best.
THE EXPOSURE
Will depend upon the strength of the negative, and
the nature of the light ; a few seconds will generally be
enough. Close contact is absolutely required to produce
sharp positives. An ordinary printing-frame can be
used.
TO DEVELOP
In a dark-room, remove the dry plate from the frame,
place it in a dish, and flow over it
•Alcohol,..........-j
Water,...........) e9ual Parts-
Then wash in running water.
DEVELOPING SOLUTIONS.
Pyrogallic Acid,.........2 grains.
Water,............1 ounce.
Made from a stock-bottle of
Alcohol,............1 ounce.
Pyrogallic Acid,.........90 grains.
Five minims of this solutions contains one grain of
pyro.