_Gravelly Wax Negatives._--The only remedy I am acquainted with is to use
the paper within twenty-four hours after excitement. I have tried the
methods of Messrs. Crookes, Fenton, and How; in every case I was equally
annoyed with gravel, if excited beyond that time; in fact, I believe all
the good wax negatives have been taken within twelve hours. The Rev. Wm.
Collings, who has produced such excellent wax negatives, 24 in. x 18
(several were sent to the late Exhibition of the Photographic Society),
informs me the above is quite his experience, and that he excites his
papers for the day early in the morning. The cause lies, I believe, in the
fault of homogeneity of the waxed paper, arising from unevenness in the
structure of the paper exaggerated by the transparency of the wax, partly,
perhaps, from a semi-crystallizing of the wax in cooling, and also from its
being adulterated with tallow, resin, &c. As a consequence of this, the
paper is filled with innumerable hard points; the iodizing and exciting
solutions are unequally absorbed, and the actinic influence acting more on
the weak points, produces under gallic acid a speckled appearance, if
decomposition has gone to any length in the exciting nitrate by keeping.
The ceroleine process, by its power of penetrating, will, I hope, produce
an homogeneous paper, and go far to remove this annoyance.
In answer to a former Query by MR. HELE, Whatman's paper of 1849 is lightly
sized, and not hard rolled, so that twenty minutes' washing in repeated
water sufficed to remove the iodide of potassium, and if long soaked the
paper became porous, often letting the gallic acid through in the
development. I have lately been trying Turner's and Sandford's papers; they
require three or four hours' repeated washing to get rid of the salts,
being very hard rolled. Many negatives on Turner's paper, especially if
weak, exhibit a structural appearance like linen, the unequal density gives
almost exactly the same gravelly character as wax, as the positive I
inclose, taken from such a negative, shows. Not only ought collodion to be
"structureless," as MR. SHADBOLT well expresses it, but likewise all the
other substrata of iodide of silver.