_Photographic Notes._--G. H. P. has communicated (Vol. vii., p. 186.) a
very excellent paper in reference to our numerous failures in the
collodion process; but the remedies he proposes are not, as he is aware,
infallible. He gives the recommendation you find in every work on the
subject, viz. to lift the plate up and down in the bath to allow
evaporation of ether. I have made experiments day after day to ascertain
the value of this advice, and I am convinced, as far as my practice
goes, that you gain nothing by it; indeed, I am sure that I much oftener
get a more even film when the plate is left in the bath for about two
minutes without lifting it out. I should be glad of other photographers'
opinion on the point.
I have never found any benefit, but much the contrary, from re-dipping
the plate in the bath; and I may observe the same of mixing a drop or
two of silver solution with the developing fluid.
I think with G. H. P. that the developing solution should be weak for
positives.
I omitted, in my description of a new head-rest, to say that it is
better to have all the parts in metal; and that the hole, through which
the arm runs, should be a square mortice instead of a round one, as is
usual. A screw at the side sets it fast; the lower portion of the
upright piece being round, and sliding up and down in a tube of metal,
as it does in the best rests, allowing the sitter to be placed in
different positions. All this is very difficult to describe, but a
slight diagram would explain it easily, which I would willingly, as I
have before said, send to any one thinking it worth writing to me for.