Atlanta semi-weekly journal. (Atlanta, Ga.) 1898-1920, 1912-09-10

With the Improvement in quality also great
reduction in price, full page half in a magazine
costing from tenth fifth of the price OF fairly
good wood engraving The process of photo-engrav-
ing includes branches-the half and the Inns
engraving. which is known also the zinc etching.
The half-tone process resulted experiments BY
Frederic J. Ives. Of Philadelphia, who made the dis
coveries leading up to it when he in charge OF
the Photographic laboratory Cornell University
in 1891 The Of this branch OF photo-engraving
is in descriptive Of the process, inasmuch
brings out by chemical and mechanical methods the
various gradations light and shade, Tone
photograph or painting which is the subject Of
ducton Ives conveived the idea of breaking up the
surface Of the picture into Ipinute dots and lines.
which in that portion print should be heavier
than in the portions to be in the lighter tones This
he accomplished by the invention of the half-tons
screen This screen is of glass. there being two
pieces of plate glass folded and cemented
gether, each piece of glass. however having been
ruled with diamond point diagonally its
face to slight depth at intervals equal to the thick
Of the ruled lines. After the surface of the
plate has ruled indicated the lines filled in
with an opaque substance. that when folded TO-
Eether stated. looking through it IS
a series Of lines with minute Transparent
openings between them. This is inserted in
the plate holder Of the used IN process work.
Immediately in front of the sensitized plate upon
which the negative is to be made The result is that
reproduction of the appears upon the Mega
tive, well the picture which is to be repro'
duced
If. instance. landscape is the subject for
production. the high light effect would predominate in
sky Of picture, and where the sky appears in
the photograph because Of the density Of the hgat
reflected from 1t through the lens Of the
the senstzed plate, haation around the light
admitted through the openings the that
line effect OF 1t is destroyed and a series OF
small dots will in the resulting halftone. Cor
respondingly, the dark portion OF the picture
necting but small amount Of light the line effect OF
the is reproduced else entirely lost in the
resulting half-ton thus leaving substantial and
solid nearly solid, surface in the resulting printing
plate. This screen is, as will readily be observed.
key to process for without 1t merely picture
could be taken. that would have qualities from
which satisfactory etching could be done In order to
adapt the process TO various grades of paper, tbs
ruled with lines of varying coarseness.
running for ordinary newspaper work, from SIS 10
100 lines TO inch for ordinary super-calendered
paper about 120 lines to the inch; and for coated
paper, from 1ss to IT'S lines to the inch
In the Photographic part Of the process in both
the haf-tone and line branches the negative that 10
made the copy is Of the wet plate variety now
almost obsolete for any purpose 1t is because
the fact that the black parts Of the copy are rs
produced negative in absolutely Transparent
line whereas in dry plate photography thin hazs
appears the line and to extent would inter
fere perfect etching After the negative has been
made from copy under consideration 1t is coated
with a solution liquid rubber and collodion, AID
after drying a minutes it is placed in bath
of acetc acid which enables the workman to remove
the fInn now transposed into thin rubber menu
which is then transferred to sheet OF piato
glass usually 10 by IS inches in size, enough
different negatives being placed this glass 10
allow the workman to handle them in wholesale
manner. After negatives have been properly
squared up size Of the required cut they
are ready printing the sheet of metal upon
which thew are to the halftone process
this metal consists copper the surface Of which mas
been coated with sensitized solution. The mega
tive is placed in printing frame and the copper laid
face down upon it, and by action of sunlight or arc
electric light print made the metal in practic-
ally the same that the gallery photographer
prints his negative upon the sensitized paper.
The line engraving is naturally done in the same
manner the half-tone, except to detail Instead
of etching in sequchloride of iron zinc plate,
upon which the line engraving has been printed, is
etched in nitric acid, that chemical being better
adapted to etching of zinc plates line
craving IT is necessary to cut the spaces between
lines to a greater depth than has appeared through
the etching process. and this is accomplished by.
routing between the lines machine that carries
what merely a movable drill
The best grade OF half-tone always Is etched
upon copper. whereas line work is almost Invariably
etched in zinc the that zinc sufhces for
the line process and has the advantage of being a
cheaper metal