68 
THE SCIENTIST. 
ings of mccliaiiiCcil or natural objects, in 
order to secure f>;reater accuracy of de- 
tail, make use of photographs on plain 
paper, that is, paj)er not albumenized, 
the picture appearing as if drawn in red- 
dish brown washes on a matt surface. 
They are called salted prints from 
the fact that the paper, before silvering, 
is dipped in a bath containing an infini- 
tesimal proportion of gelatine and a 
small percentage of ammonium chloride. 
In practice it is better to buy Clemon's 
plain salted paper from any photo sui>- 
ply house and silver it as required, than 
to mess around salting it for one,'^-self. 
The silver solution for plain paper is 
made up of pure distilled water or fil- 
tered rain-water, 9 ounces: nitrate of 
silver 1 ounce. Dissolve the silver in the 
water and separate three ounces of the 
solution from the rest, say in a graduate. 
To this three ounces add liquor ammo- 
nia, drop by drop, until the oxide of sil- 
ver precipitation first produced is re-dis- 
solved and the solution becomes clear; 
then add to it the remaining six ounces 
of solution. Oxide of silver will again 
be formed, but can be allowed to settle 
to the bottom and remain there until the 
solution is all used. The solution is ap- 
plied to the paper with a small swab of 
clean cotton, or wool, or a pad of canton 
flannel. It is well to filter a little of the 
solution tor use each time, thus avoiding 
soiling the paper with the scum which 
collects upon the surface of the liquid. 
Care should be taken to apply the solution 
evenly and lightly, otherwise the surface 
of the paper may be roughened. After 
silvering, the paper is hung up in a per- 
fectly dark room till dry, which drying 
may be assisted by artificial heat. When 
handling the paper, great care is neces- 
sary not to finger-mark or soil it, each 
careless touch coming up on the work 
when printed and fixed. Print under an 
ordinary negative until all details are up 
satisfactorily and only slightly deeper 
than re(iuired in the finished prii>t, for it 
w^ll not lose much in fixation. It does 
not require toning. When printed, 
1 usually immerse in a bath of salt water 
for five minutes, then rinse and fix in 
fresh hypo-sulphate of soda solution, 
strength one ounce to seven, for ten to 
fifteen minutes, then put in a tray and 
wash under l unning water i^m i<,v liilteen 
minutes, or byjcompletely changing the 
w^ater six or seven times, letting it stand 
five minutes each time,,|',l'.o eliminate last 
traces of hypo, fiow with a bath contain- 
ing one or two drams of a solution of ace- 
tate of lead, strength 1:8, in each pint. 
Let rest in this for ten minutes, rinse two 
or three times, and hang up to dry, or dry 
between clean blotters. When dry, brush 
the backs over with f j-esh starch paste, 
and paste do\yai on smooth heavy white 
card. Lay between clean dry blotters un- 
derweights to dry. The drawing can 
then be outline dcaref ully and solid blacks 
pajnted in, even a considerable amount 
of shading done. When the artist feels 
that he has carried the work as far as 
needful on the print, he lets it get quite 
dry, often by stove heat, and flows it 
with a solution of water 8 oz., alcohol 
8 oz., corrosive sublimate I oz. This so- 
lution will keep indefinitely and can be 
returned to the bottle and used over and 
over 
The print will bleach ou^t, ,to 
nearly white paper, and when dry the 
drawing can be finished up a,s desii ed. 
It is necessary to keep the drawing thus 
made, in the dark, if nnich time is to 
elapse before it is engraved, as a slight 
browning may occur in a strong light. 
A modenite amount of exposure to half- 
light indoors v/ill not aff'ect it. The ink 
used should be of the best quality and 
freshly rubbe<.J i^ip, s^n^l must be bone dry 
when the bleaching ^olution is poured on. 
The alcohol diminishes the action of the 
water on the ink, the paste and mounts. 
The drawing will cockle some when 
flowed but will dry out smooth and 
straight. 
