The Colfax chronicle. [volume] (Colfax, Grant Parish, La.) 1877-1981, 1886-11-13
pHoTo-nRlNTlMo.
Photogravure for Book illustrations and
Zinco-Types for Newspaper work.

Photogravurs for Book illustrations cd
zinco-rypes for Newspaper work.
The use of Photographic negativ.
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 Of
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 ap
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
taste for chemistry led him to expert
ment with the new toy, and in 1848 he
published the fact that 1t 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 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 a film of gelatine. which. after
sensitizing by means of bichromate OF
potassium, was exposed to light under
negative. When cold water was ap-
piled, the parts Enacted upon by
light swel1ed up and SO formed an
image in relief from which mold in
| plaster or other suitable material could
be taken. ife
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 70 adhere. In 1856 ne
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. 1Poiteyin was,
however, too much engrossed In in
vention to prosper in business, and he
sold out the shop to Len1ercier, who
still carries II on. and turned his at
| tention again to experiments In 1867
| 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 Lnynes awarded him the prize
offered for advances in applied science,
and at the exhibition Of 1873 he was
adiudged a. gold medal and an honor
arium of seven thousand francs IN
recognition of bis services. He died at
Confans, March 4. 1882.
Some of tho best work done In THU
country with processes growing out %
Poitevin's invention is that known
under the general head of photo
erayure, which is printed directly froI
an etched plate. The plate is covered
| with a sensitive film and afterwards
etched, the acid acting where the !igh
coming through negative has fallen
From such a plate, using . copper-Plat.
press, the New York company which
makes speciality of this work pro
duces very beautiful results. For fin
books, where cheapness is not sought
the photogravure answers the purpos'
admirably, for any number of impress
! sions can be taken. The same compan.
also uses the gelatine plate process, a
modified by Mr.. C. T. Roche. Some Q
the large plates and reproductions o
sepia sketches, done in this way, ar
admirable specimens of the art at it
best.
For purposes OF newspaper illustrs
ton, especially in colOrs, zincograpn
is much used in Europe and, to small
extent, in this country. Zinc plates ar
coated with an asphaltum film and eS
posed under negative or drawing froI
ten TO sixty minutes. Asphaltum i
certain conditions is sensitive TO light
Where light acts acid can penetrate t
| the plate, and il is etched in the usus
manner. When it is desired to prlr
in colors, negative is prepared e
each color, one allowing no light
J pass except for yellows, another redi
etc. Many German and French new
papers are illustrated by this process
The colored plates in the last Christms
} number Of the Paris Figaro, so largel
sold in this country, were photo-zlnc'
, types.-N y. Post.
OVER NIAGARA.