The Bossier banner. [volume] (Bellevue, Bossier Parish, La.) 1859-1952, 1886-10-07
PHOTO.PRlNTIN0.

PHOTO.PRlNTING.
Photograyure for Book Illustrations and
Zinco-Types for Newspaper Work.
The use of a Photographic negative
in connection with photographic sur
, face has become of such Importance
for almost every sort of illustrated
work, from the business circular to the
finest books of art, that the name oi
Poitevin, the French inventor and real
father of the process, deserves to be
better known than it is Louis Al
phonse Poitevin was born at Contains,
in the Department of the Santhe,
| France, in 1919. His bent towards APP.
piled chemistry led him early to the
Ecole Centrale, in Paris, where he de-
voted himself almost entirely to chem.
ical and mechanical studies, leaving
the school in 1843 with the diploma of
| civil engineer. His first appointment
was that of chemist in the national
salt works in the east of France, in
which capacity he introduced many
improvements in the processes and
machinery used, and also in the manu-
facture of potash, sulphuric acid, etc.
When photography came upon the
world as scientific curiosity, Poitevin's s
taste for chemistry led him to expert
ment with the new toy, and in 1S4S he
published the fact that it was possible
to produce an electro deposit of cop
| per upon the whites of the daguerreo-
| type image. His work in this direction
led to the discovery of a method of pho
to-chemical engraving upon metallic
plates coated with gold or silver, for
which he received the medal of the
Societe Encouragement des Arts.
Soon afterwards he began work upon
the study of the action of light upon
bichromated gelatine, He first applied
| himself to the production of molds in
relief, and patented in 1855 his hello
plastic process. which consisted in pre-
pairing film of gelatine, which, after
sensitizing by means of bichromate of
potassium, was exposed to light under
anegative. When cold water was ap-
piled, the parts unacted upon by
light swelled up and so formed an
image in relief from which a mold in
plaster or other suitable material could
be taken. 7, 80
His next achievement was the ink
process. He, discovered that the sur
face of the bichromated gelatine film
after exposure to light became. re-
pellent of water, while it permitted a
greasy ink to adhere. In 1856 he
established workshop for the pro-
duction of pictures by this process.
Some of his early plates are in the
possession of Mr.. Edward Bierstadt, of
this city, and compare favorably with
| much work of to-day. Poitevin was,
however, too much engrossed in in
vention to prosper in business, and he
sold out the shop to Lemercier, who
still carries it on, and turned his at
tention again to experiments. In 1862
he perfected system of carbon print
ing, from which the present processes
are derived. He also published re-
searches in connection with the action
of light upon various salts of iron. The
Due de Luynes awarded him the prize
offered for advances in applied science,
and at the exhibition of 1878 he was
adjudged a gold medal and an honor
arium of seven thousand francs in
recognition of his services. He died at
Conflans, March A. 1882.
Some of the best work done in this
country with processes growing out of
Poitevin's invention is that known
under the general head of photo
gravure, which is printed directly from
an etched plate. The plate is covered
with sensitive film and afterwards
etched, the acid acting where the light
coming through a negative has fallen.
From such a plate, using a copper-plate
press, the New York company which
makes a speciality of this work pro-
, duces very beautiful results. For fine
books, where cheapness is not sought.
: the photogravure answers the purpose
admirably, for any number of impress
sions can be taken The same company
also uses the gelatine plate process, as
modified bv Mr.. G. L. Roche. Some oil
the large plates and reproductions OF
sepia sketches, done in this way, are
admirable specimens of the art at its
best.
For purposes of newspaper illustra-
J ton, especially in colors, zincography
, is much used in Europe and, to a small
extent, in this country. Zine plates are
| coated with an asphaltum film and ex-
posed under negative or drawing from
: ten to sixty minutes. Asphaltum in
, certain conditions is sensitive to light.
: Where light acts acid can penetrate te
: the plate, and it is etched in the usual
. manner. When tits desired to print
3 in colors, negative is prepared fol
| each color, one allowing no light te
: pass except for yellows, another reds
J etc. Many German and French news
l papers are illustrated by this process
q The colored plates in the last Christina;
. number of the Paris Figaro, SO largel,
8 sold in this country, were photo-zinco
t types.-N Y. Post. ti# t1tfsAt
4 The Presbyterians of this country
0 both Northern and Southern, are T.
I meet in General Assembly in Philadel
I phia in 1888. 1t win be the one hun
. dredth anniversary of the Presbyteriai
q General Assembly in the United States