Distilled water 10 oz.
Sulphuric acid 3 drops.
Protosulphate of iron ½ oz.
Formic acid 1 oz.
The formic acid is also a most capital addition to the protonitrate
of iron, and either this or the former liquid produce most brilliant
positives leaving a fine coating of white dead silver. I may also make
mention of the improvement I have made in the albumen paper, which
consists in the introduction of the chloride of barium into the albumen,
in place of chloride of ammonium or chloride of sodium. Take
Water 6 oz.
Albumen 6 oz.
Chloride of barium 7¼ dr.
Whip these up, till they are converted entirely into a white froth; when
this has settled into liquid, pour it into a tall jar, and allow the
precipitate, which will then separate, to settle completely, and strain
the supernatant liquid through fine muslin. The paper, being laid on the
surface of this fluid for a space of from five to ten minutes, may be
taken off and hung up by a crooked pin to dry, and then ironed. It is to
be sensitized with nitrate of silver, 120 grains to the ounce of water.
The setting liquid I use is prepared according to the formula given by me
in Vol. vii., p. 534. of your journal, except that I prefer to use half
to one grain of pyrogallic acid, and 120 grains of chloride of silver.
This paper must be soaked for a few minutes or so in rain water, after
being printed, before being placed in the hypo.; the presence in the
water of any salt seems to destroy the tone of this paper.
Florian, Torquay.
_Muller's Processes--Sisson's Developing Solution._--I am glad to find
that I have called the attention of your photographic correspondents to
Mr. Muller's process, as detailed in _The Athenæum_ of Nov. 22, 1851,
which seems to have been strangely overlooked and neglected. As your
correspondents have induced you to reprint the article, perhaps you will
also yield to my request, and reprint an article from the same journal of
later date (Jan. 10, 1852) containing another process, more economical
and more sensitive than the other, invented also by Mr. Muller, and the
value of which I have proved. In that, as in the other, there is no
developing agent required. To save time I have copied from my note-book
the article itself, and append it to this communication.
A photographer of several years' standing informs me that my developing
solution produces excellent negatives upon glass, and that he has been
trying it as a bath with success. He writes me:--"I use your developing
solution for negatives only; and by using a very small opening, say about
3/10ths of an inch diameter, single achromatic lens, I have produced
negatives in one minute, which print most beautiful bright positives.
The views I have taken and developed with your solution were without
sunshine, the sky very cloudy, three o'clock p.m. The collodion was
prepared by Messrs. Knight & Son."
Since I received his letter I have tried a negative so developed, with
the best success; and I attribute the success to the fact that you may
go on developing with that solution any length of time almost, without
any fear of spoiling the negative, thus getting thickness of deposit; and
that the deposit on pictures taking so long a time to develop has a very
perceptible yellow tinge, which, like the gold in Professor Maconochie's
method (detailed in _Photographic Journal_ for this month), stops the
chemical rays.