The republic. [volume] (Washington [D.C.]) 1849-1853, 1850-06-28
From the Philadelphia North American.
Improve ments I'm Ph hot0urnuhv

Photography proper--as distinguished from the
Daguerreotype arts making great advances in
England. where. since the discovery Of M. Niepce
of the mode of taking negative pictures on albu
menized glass plates, (hyalotyPes) the art has be-
come popular among considerable class of anna
tours, to some of whom it ia indebted for valuable
improvements. Mr.. T. A. Malone describes. in
the London ALhenGum of June J. process which he
has adopted, involving one two points of novelty,
by one Of which he is enabled to convert negative
picture Immediately into positive one.
ton of caustic alkali washing it with water, and
drying it with a CLOTH and, Just before applying
the abumen, he breathes upon it, and rubs ii with
new blotting paper followed by cotton wool. to
move fibres and dust; the last being indispensable
to prevent the absorption of iodine by such parti
cles, whereby the picture would be spotted and
spoiled The albumnous liquor consists of equal
measures of water and white of egg, beaten toge
ther to foam, and then strained through paper
cone or filter, having small aperture at its apex
He pours the albuminous liquor on the glass, pre-
pared as previously described, inclining the plate
from side TO sde until it is covered allows the ex
cess to run off at one of the corners, holding the
plate in nearly vertical position; and, whenever
the liquid ceases to drop rapidly, he breathes on,
warns the lower half of the plate-the moisture of
the breath in the case, the warmth In the
other, causing il to flow more freely; wiping the
edges continually promotes the operation. The
great object is TO procure uniform coating. When
the glass is sufficiently dripped, it is dried for
which purpose Mr.. M. a double-rin gas bur
swers as well, except from the danger of dust. The
film, he adds, when dry, is quite free from cracks,
and s thin and transparent that the briliancy Of
the glass is unimpaired that it is almost neces-
sary to mark it to know which side has been coated
The next process is TO iodze the albuminous film;
the plan OF effectng which, with the subsequent
steps for procuring and fixing the negative picture,
we describe in his own words
"Dilute pure iodine, :" he says, "with dry white
sand in mortar, using about equal parts Of each
Put this mixture into square glass trough, and
over il place the albumined plate soon the
latter has become yellow in color, resembling beau
tiful stained glass, remove il into a room lighted
by only candle through a translucent sub
stance-yellow calico, for instance. Here plunge
it vertically and rapidly into Deep narrow vessel
containing a solution of aceto nitrate Of silver,
made by adding three ounces OF nitrate OF silver to
two of glacial acetic acid diluted with sixty
ounces of distilled water Allow il TO remain until
the transparent yellow tint disappears, to be sue
ceeded by milky looking film OF iodide OF silver
Washing with distilled water completes this opera
ton. The plate is now ready for the camera. After
il has been submitted 10 the action of the light,
pour its surface saturated solution Of gallic
acid. negative Talbotype image on albumen IL
the result. Washing with water, before and after
immersion in solution Of one part Of hyposulphite
of soda in sixteen parts of water until the yellow
tint is removed from the shadows, completes the
process"
II is by the following slight variation of the pro-
cess at the period when the picture s being treated
with gallo acid, that II Ia converted into positivs
one.
HWhie the gallic acid 10 developing its reddish
brown image" says Mr.. Malone, % pour upon the
surface strong solution Of nitrate of silver the
brown image deepens in intensity until il becomes
black. Another change commences: the image
begins TO grow lighter, and, by perfectly natural
magic, finishes by converting the black into white,
presenting the curious phenomenon Of the conver-
sion Of a Talbotype negative into, apparently, a
Dagucrreotype positive. but by very opposite
agency, no mercury being present; metallic silver
fnuha hlVl here DrOducing the llphts while tho
Daguerreotype, it produces the shades Of the pic
ture."
Professor Whcatstone suggests the application OF
Malone's process TO blackened wood or backened
ivory; and the Alen~un intimates that M. Ballard
has Just communicated a similar discovery TO the
Academy Of Sciences.