_Replies to Photographic Questions._--SIR WILLIAM NEWTON is right
respecting the active properties of sulphuric acid; it should therefore not
be stronger than merely tasting of the acid; but it has appeared to me to
possess a superior effect in setting the alkalies free. I believe muriatic
acid would have precisely the same effect, or Beaufoy's acetic acid, though
it would be rather expensive. Starch would be invaluable both for positives
or negatives, if it could be laid on perfectly even; but if pinned up to
dry it all runs to one corner, and if laid flat it runs into ridges.
Perhaps some artist may be able to favour us with the best mode of treating
starch; its non-solubility in cold water makes it an invaluable agent in
photography.
The above includes a reply to MR. J. JAMES' first Query: to his second, the
solution may be either brushed or floated, but all solutions require even
greater care than doing a water-colour drawing, to lay them perfectly flat.
The remaining questions depend for answer simply on the experience of the
operator: the formula given was simply for iodizing paper; the bringing
out, exposure in the camera, &c., have been so clearly described lately by
DR. DIAMOND, it would be useless to give further directions at present.
G. H. should dispense with the aceto-nitrate and gallic acid, and bring up
with gallic acid and glacial acetic acid only. This makes no dirt whatever,
and is quite as effective. The marbling {266} he alludes to proceeds from
the sensitive solution not being sufficiently dry when put into the camera.
Even if prepared paper is blotted off, which I think a very bad plan, it
should have some time allowed it to dry; also the faintness of the image
depends either upon not giving time enough, or the aperture he uses for his
lens is much too large; or again, he has not found the true chemical
focus,--it varies in single meniscus lenses sometimes as much as
three-eighths of an inch nearer the eye than the visual:--all these are
causes of indistinct images, and require patience to rectify them.
I beg leave to subscribe entirely to MR. W. BROWN'S remarks on the subject
of Mr. Archer and collodion. I have one of Mr. Horne's handbills,
circulated with the first samples of collodion, headed "Archer's prepared
collodion" in 1851, and had some of the earliest in the market. That Mr.
Archer should fail in trying his own preparation goes for nothing at all,
because, at the best of times, and with the most skilful, failures are
often numerous and mortifying, in photography above all other arts;
therefore, unless some more correct data are given, the merit rests
entirely on Mr. Archer.