Ewell.
_Developing Paper Pictures with Pyrogallic Acid, &c._--Have any of your
photographic correspondents tried developing their paper negatives with
pyrogallic acid? If so, perhaps he would favour the readers of "N. & Q."
with the result of his experiments.
In DR. DIAMOND'S process for paper negatives, he says the paper, after the
iodizing solution has been applied, must be dried before soaking in water.
I wish to ask whether it may be dried quickly by the fire, or must it be
dried spontaneously by suspension, &c.? Again, how long must the paper
remain on the sensitive mixture: must it be placed on the sensitive
solution, and _immediately_ taken off and blotted, or placed on the
sensitive solution, and _after some time_ (what time?) taken off and
_immediately_ blotted?
Have any of your readers substituted iodide of ammonium for iodide of
potassium, in preparing paper, collodion, &c., and with what success? And
have they substituted nitrate of zinc for glacial acetic acid, as
recommended in a French work, with any success?