The ferrotype and how to make it - The Grian Press

58
THE fekrutvjm:.
remains unchanged ; the freedom from all trace
of acid is insured by adding a little ammonia
before the last washing. Cotton thus prepared
should dissolve perfectly and instantaneously in
ether containing a little alcohol, without leaving
a fiber behind, and the film it produces be of the
greatest strength and transparency.
Having obtained good pyroxyline by purchase,
or by the above process, the next point of inquiry
is with regard to the solvent; many experiments
have been made to ascertain the proper propor-
tions of ether and alcohol to produce the best
Collodion, having regard to all the qualities con-
sidered necessary to a good article. As ac-
cordino^ to the definition at the head of this ar-
tide, gun-cotton will dissolve in ether, it might
be asked why add alcohol, and be answered by
giving a variety of reasons: first, the solution in
ether alone could not be sensitized, and would
evaporate to dryness, or ''set" so quickly as to
unfit the film for immersion in the bath ; as, for
instance, a mixture containing one-eighth of
alcohol would prove quite unfit for photographic
purposes, it being almost impossible, even with
the most rapid coating and immersion of the
plate, to obtain a film of uniform sensitiveness
and opacity throughout.
It has been found that the proportion of three
parts of alcohol to five of ether produces the best
results, giving without the least difficulty a film
beautifully uniform and highly sensitive, and at