IMPROVE- MENTS IN PHOTOGRAPHIC PRINTING FRAMES
Year: 1866

page_text: PROVISIONAL SPECIFICATION left by Lorenzo Field at the Office of
the Commissioners of Patents, with his Petition, on the 6th July
1866.
I, LORENZO FIELD, of Birmingham, in the County of Warwick, Cabinet
Maker, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN PHOTOGRAPHIC PRINTING FRAMES," to be as follows:-
My Invention consists in the arrangement herein-after described of the parts
of photographic printing frames used for printing positive photographs from
negative photographs. Photographic printing frames made according to my
Invention are especially applicable to the printing of positive photographs upon
opal glass, but may also be used for printing photographs upon paper, and
generally for all such purposes as ordinary photographic printing frames are or
may be applied to. I arrange the parts of photographic printing frames as
follows:-I employ two flaps carrying respectively the negative and the paper
or material on which the positive is to be printed. I will call these parts
the negative and positive flaps respectively. The two flaps are hinged
together so as to. close upon one another, and studs on the edge of one take
into holes in the edge of the other, to ensure the flaps closing truly upon one
another. The negative flap consists of a frame carrying an inner frame in
which a sheet of glass is fixed to support the negative. The inner frame is
connected with the principal or outer frame by means of springs at its corners,
so that the negative can take an exact bearing on the positive surface pressed
against it during printing. When this bearing is obtained the inner frame

page_text: can be fixed by means of clamping screws. The positive flap consists of a
frame carrying a panel having a number of parallel slots in it; an ordinary
pneumatic plate holder is fixed in any required position on the panel by means
of the slots, and the plate of opal glass or a board carrying the positive paper
is held by the pneumatic plate holder. By the facility which the slots afford
for changing the position of the pneumatic plate holder the surface to be
printed can be brought to any required part of the flap so as to take a print
from any part of a negative. When a positive is to be taken on opal glass,
the said glass is held directly by the pneumatic plate holder. When a positive
is to be taken on paper, the paper (prepared in the usual way) is placed on a
board or panel, and held by spring strips at the edges of the said board or
panel, and the said board or panel is held by the pneumatic plate holder.
The negative being placed in the negative flap, and the opal glass or paper in
the positive flap, the latter is closed or turned down upon the former and
secured by hook fastenings. The bearing of the positive surface upon the
negative is obtained in the manner herein-before described. The frame is
exposed to light in the usual way, and the progress of the printing may be
examined from time to time by raising the positive flap from the negative
flap. In order to fix the negative steadily in the negative flap, the said flap
is provided with a metal bearing at one end and a bow spring at the other,
between which the negative is held. A series of frames similarly furnished
with metal bearings and bow springs is provided to fit in one another to be
used with negatives of different sizes.