A Manual of Photographic Chemistry, Including the Practice of the Collodion ProcessHardwich, T. Frederick
Science
A Manual of Photographic Chemistry, Including the Practice of the Collodion Process
Hardwich, T. Frederick
Photographic chemistry; Photography
_Mode of applying the Albumen._--Cover the moist film with the Albumen
in the same way as advised for Collodion (p. 216), pouring on at once a
sufficient quantity to cause it to spread in an even and undivided sheet;
otherwise a veined appearance may be produced, which will show in the
development. Return the excess of Albumen into the bottle, and pour it
once again upon the plate: the film will remain clear and transparent, if
the whole of the Nitrate of Silver has been properly washed away from the
Collodion. Lastly, stand the plate nearly vertically on blotting-paper to
dry. This will occupy five or six hours; but the process may be hastened
by artificial heat.
After the Albumen solution has been used to coat a number of plates
successively, it becomes diluted with water; the result of which is, that
unequal intensity of image is produced at the upper and lower edge of the
film.
The iodized Albumen plates are at this stage of the process nearly or
quite insensitive to light, and may be preserved unchanged for many weeks.
_Sensitizing the Albumen film._--When the plate has become thoroughly
dry, it is again introduced into the Bath of Aceto-Nitrate of Silver,
and allowed to remain for one minute: then washed with water in the same
manner as before, but with even greater care, in order to obviate clouding
in the development. If blisters should form on drying, it will be found
useful to hasten the process by holding the plates to the fire--or a hot
iron may be placed in the centre of a covered box and the glasses reared
up round the sides. They will thus dry quickly, and there will not be time
for the Albumen to swell much by imbibition.
_Exposure in the Camera._--This may be performed at any period within a
few weeks from the date of preparation of the plates. For a landscape view
with a small Stereoscopic single lens, allow about three minutes in the
winter, or one minute and a half in the summer.
_Development of the image._--This can be deferred as long as fourteen days
after the exposure, with successful results. Pour water over the plate
until the film is thoroughly wetted; then cover it with a solution of
Pyrogallic Acid containing one grain of the acid to the ounce of water,
and twenty minims of Glacial Acetic Acid. Two drops of a neutral solution
of Nitrate of Silver made with forty grains of Nitrate to the ounce of
water must be previously added to each fluid drachm of the Pyrogallic.
The development, in the case of a landscape view taken with sunlight,
commences almost immediately, and may be completed in about ten minutes,
but the time occupied in developing will vary greatly with the length of
exposure, the quantity of Nitrate of Silver, and the nature of the subject
copied--a badly lighted interior, for instance, often taking an hour or
longer to appear in all its details. If the developer should discolour
before the proper intensity has been obtained, pour it off and mix a fresh
quantity.
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