_Mr. Pumphrey's Process for securing black Tints in Positives._--The
importance that appears to be attached by some of thy correspondents to the
stereoscopic appearance of photographs, induces me to call the attention of
those who may not have noticed it to the fact that, as all camera pictures
are monocular, they are best seen by closing one eye, and then they truly
represent nature; and the effect of distance (which so often appears
wanting in photographs) is given with marvellous effect, so well indeed as
to render the use of a stereoscope unnecessary. Like other photographers, I
have been long seeking for a method, easy, cheap, and certain, for
obtaining the black tints that are so highly prized by many in the French
positives; and having at last attained the object of my search, I lose no
time in laying it before my fellow-operators.
I obtain these results with a twenty-grain solution of nitrate of silver, a
fact that will, I think, commend the plan to most operators. Thou wilt be
able to judge of the result from the inclosed specimen.[7] I use Canson's
paper, either albumenized or plain (but the former is far preferable). If
albumen is used, I dilute it with an equal measure of water, and add half a
grain of common salt (chloride of sodium) to each ounce of the mixture.
This is applied to the paper with a soft flat brush, and all bubbles
removed, by allowing a slender stream of the mixture to flow over its
surface: it is then hung up to dry, and afterwards the albumen is
coagulated with a hot iron. If the paper is used plain, a solution of
common salt (half a grain to one ounce of water) is placed in a shallow
tray, and the paper floated on its surface for a minute, and then hung up
to dry. Excite, in either case, with an ammonio-nitrate of silver solution
(twenty grains to one ounce of water), by floating the paper, prepared side
downwards, for one minute, and hang up to dry.
Print tolerably strongly, and the proof will be of a reddish-brown. Fix in
tolerably strong solution of hypo. sodae (I never weigh my hypo., so cannot
give the proportion), that either has been in use some time, or else, if
new, has been nearly saturated with darkened chloride of silver. When
fixed, remove the proofs into another vessel of the same solution of hypo.,
to which has been added chloride of gold and acetic acid. The way I do this
is to dissolve one drachm of chloride of gold in two and a half ounces
(1200 minims) of water. Of this I take twenty minims (which will contain
one grain Au Cl_3) and forty minims of acetic acid (Beaufoy's) for every
dozen proofs (of the size of 7 x 9 in.), that I mean to operate on, and
having mixed the gold and acetic acid with the solution of hypo., place the
proofs in it till they attain the desired colour: they are then to be
washed and dried in the usual way.
Knowing that so cheap and easy a process for obtaining these tints would
have been a great boon to me a short time since, I lose no time in
communicating this to the readers of "N. & Q." I shall feel a pleasure in
explaining the plan more in detail to any photographer who may feel
disposed to drop me a line.