Omaha daily bee. (Omaha [Neb.]) 187?-1922, 1912-02-24
MAKING OF A "HALF-T TONE"
Methods Of Modern Illustration En-
ployed on Newspapers.
DETAILS OF THE PROCESS
Perfection of Apparatus Makes Pos
sible Reproduction of Picture
Ready for Printing In
One Hour.

Modern illustrations have been revoiu-
donired by the so-ealled "half-tone"
method Of making from photographs
blocks that may be printed in an ordI-
Eary press and that show not only blacks
and whites. but all the graduations be-
tween these-the half and other frac-
tionsl 'tones"-once thought TO be be-
yond the power of ordinary printing
These half-tones. as in hand engraving.
are produced by minute subdivision Of
the blacks and whites. varying all the
way from sparse white dots on the black
ground. for the darker tones. to black
dots on white ground for the lighter
ones. with all possible graduations and
admixtures for those between The great
discovery that made the process possible
was not this mixing OF blacks and whites,
reduced TO tiny specks, for that was
known long ago TO every engraver. but
the method OF producing these mixtures
all ct once by the use OF photography
with the aid OF screens Of ruled glass.
The making Of the so-cslled process
block In all its detail is described by
II. +. Rea in knowledge Uondon. De-
cemberl In an article from which we
quote as follows:
"a block must be made capable Of
printing side by side with type, and it
must be able TO give all the range OF
tones OF the original from black to white.
II is made TO do this by having its sur
face cut up into very large number of
dots or squares-so small as TO be, as
a general rule, unnoticed by the naked
eye-which can catch the ink when the
roller goes over them and which imme-
diately afterwara print the picture.
First Thing to Consider.
THE blockmaker has first to consider
when he gets the photograph or drawing
which is to be reproduced-what sort of
paper the block is to be used upon.
whether rough or art paper. The better
tho paper is the greater number of dots
which can be made and the closer they
will be together. The original is then
pinned up on the copying board. which
is illuminated by two powerful arc lamps.
and photograph Is taken OF II. which
may reduce or enlarge Il, according to
the size OF the block wanted. and which,
at the same time, brings the dots into
existence.
The dots are obtained by interposing
in the camera, between the Photographic
plate and the lens, a ruled screen which
Is made by having two diagonally ruled
glass plates sealed together. the result
being cross-iined mesh. The image
passing through this gets cut up into a
series OF dots and sQuaros-ranging
gradually from fine black dots in the
transparent parts of the negative to
squares IN the half-tones and transparent
dots In the high lights. The mesh of the
screens varies much--renging from fifty
lines TO the inch for very heavy or rough
printing to 400 lInss TO the inch for the
most careful and finest art printing. The
most useful screens have 80. is3 and $50
lines to the inch and these are. as gen
sral rule. the sizes used In connection
with Illustrations for magazines. In the
case OF the daily papers-which are very
rapidly printed on fast running machines
the illustrations require screens with a
much more open mesh-usuaIly OF from
ssventy-fivs TO 100 lines to the inch.
"heu ~ ope'a euo
screen " 'ho ieeuisu u,s non .he
sirsd-he makes his first exposure. which
:" s"o "o wv A'n !" 'He
aArAer parts " eie sN@ he 'Ae"
places 'ns sap oh 'ne iohS' pu's III
persef s'op anu eAposes n' he' ~
.nis way. ssos uoe 'orm~uoh % my
aetsii' ihs 'n.1u eAposuie."n sun
larger STOPS Tor ,hs oot iormAiioh IN
tne n'kh nsn's' 'ome opeIs'ois niahs
oniy 'No eAposu esop'
used vary srea, asa. ine exposures
VIZ - - 80
aie usea - 800 iv"s
noh 'ae ooe =. s.e 1"s' -. aae
enc Oh 'ns .h''u-'s'es rom minute
ana mar 70 ureo MINUTES u an arc
amp Oh 'ne ehe'oseu ope ~ useu' -
TINS gives tne greater pefeen'ase OF fio-
let or acuNe rays Oh nsnt' 70 winch tne
plates are most SenAuFe- Inc exposure
with the open type OF arc lamp Is about
three times as long.
The exposed plate Is now developed IN
the ordinary way and arterWard reduced
IN density BY letting cutung-out
solution flow over II until the dots are
Of the size necessary to give the requisite
brightness The finished negative is now
dried and printed on copper, which has
been sensitised> with white OF egg, nsh
glue and bichromate OF ammonium The
print on the copper plate is developed
in water, which dissolyes away the soin,
ton not acted upon by the light, and Il