The sun. [volume] (New York [N.Y.]) 1833-1916, 1897-04-04
PHOTOGRAPHY IN COLORS.
A Process which, Prof. Grady OF Paris Says.
Furnishes the solution OF the Problem.

Prot. Grady read a paper on photoGrap ply in
colors before the Academic des Sciences in
Paris recently. and not only explained every
detail OF the process and gave the exact formula
to be followed. but also showed some remark
able photographs In co'ors taken By himself.
In almost all the attempts made previously
10 reproduce color IN photography the processes
h,ave depended upon tAc phystcn! effects OF tho
interfer. nee OF light. Prof. Grady has depend
ed entirely uTon chemical action. His eXpla-
nation OF the process. A. described in his paper,
when a plitc of metallic silver Is exnosed in
the dark TO the acton Of chlorine a series OF
yellow through rel to blue. II the same plato
be attcrwaid, exposed 10 light the action Is re-
n EfrT nSrc w liz n siiyr srS "hIor rr!ns di ne rn% : IN J b %h,' e;
silver nitrate. hs subjected 10 feeble blue light
blue sub-chlorIde will be produced w%hichwill re-
tain a large PROPORTION or Tho ORIGINAL chlorine.
containing still less chlorine. The yellow is Sc
gray ish yellow sub Chlorine OF silver can he pro-
duced. il Is not sufficiently pure in color or
mic acid or IL chromate Il introduced. giving n
Eo!don yellow. complementary to the blue vin-
let OF the silver. which is DEGRADED by tho
"UEder the influence of blus light the blue
suh.ch!or!de is not, sensitive. and remains tho
same. but the rcd. II lnercnric, chloride be
into the blue. II chronic acid te present also
the yellow becomes oxidized to L!ue. 80 that
."Cnhcr yellow light the chronic acid is not
ff orinerr.,r cut bl e = I.II I DOSING t1sprS. chISr Iis
and nmalgamRting with mercury.
"Unaer red light the red sub. chloride re-
mains unchanged. but the blue Is changed by
tho rcd nrarEe rays into red sub.chloride.
White Light nr9dnces b,ae or sreenish vel;
in tho dry or moist condition.
secure, permancncy. the yellow Is fixed
renders the chromnte insoinblc. The blue and
red are obtained by Introducing blchloride OF
mcr'ury and salt into the coating Of the paper.
These two substances keep up n state OF eGui-
lihrtum ms regards tho action OF light on tho
chlorine. SO that the blue and red sub-chlo-
rides ietain their composition indefinitely. Th!l
fixing. can only take place after the waite has
been hxed. except on saltcd and aihumentzed
method OF fixing tho white cannot ic applied,
Therefore completes ilNation can only be Sc
cured with sriat'no rn.ers. and this Is the
most important FO:nt OF The discovery.
THE trouble found for a long time was that
the vioiet-bluo silver compound Produced BY
without 'erinusly affecting tho blue OF the
print; Tho first method tried was ono in
%eoIuhlc. rs In the Derchlorido OF iron process.
1t WAS found that the g%clat!ne bccnmr Iess SOL
light rendered the g.lar,no completely soluble.
yellow liSht a little less so, led still n little less
soluble. and blue nlmost entirely insolublr. The
g~el9tlnc IN, melting removed the chloride.
which would have become blue. subsequently 10
h%Sntion. on exposure 10 light. Thus. In the
first method. the yellow was fixed with acetnte
o. lead. the white by washing with warm water,
and tho red aid blue by salt and blcilloriio OF
mercury.
The first method could only lie carried ont
With rmrer prem red rs follows: Gclatinu.ChlO-
ride paper Is allowed To become blue. almost TO
the violc; stage, by tmme-sing II In n bath OF
Mater 80, .,.t. '''''' 100
iydrochloric ncid !
and exposing il to dilfusei liGht. then dipping
II. whoa dry, into
Bichromatc Of ipooiia,,6h.. ...:,.:.,..:: "
1T is dried afrcsli and exposed anew until
nll the gelatino Is lust rendered !nsnluhlu. The
paper is hen ready to be sensaii2cd for colors
in the following bath:
M,eI.r ''''''''''''' ''''''''''''''' q ounces
Nlhrif h'li ..-'''''''.'' '.'.'.,. .'.,s'' " drops
herrNllr nitrate OBSERVATION-DISCLOSURES urtchm.
lShrochlof' i"lu '''... ............., h draHhina.
sulpnnTN h,il '''.'..'..''.''...' ',,,. = Hra'hhl'
Chronic acid As grains.
Suld mum ''''''''''' ''''''''' '''"u grams
This paper must lie employed wet. Tho
results so obtained arc most Interesting. Bat
for practical work tho lapcr prepared In tho
second manner should be used.
I'm this method the Hight renders the CELIA
tine Inspluble. as In tho carbon process. Celia
blued rs above, then dipped In a birhromuto
bath. and then in nitrate OF mercury. When
dry. IL In printed 80 as to reproduce the colOrs.
After this 1t is treated with acetate Of lead;
then the image 10 transferred on to another
paper and washed. as In tho carbon process.
Finally IL 10 passed thronRh q bath OF bichlo-