FIXING, INTENSIFICATION, ETC., OF NEGATIVE. 81 
XI. FIXING, INTENSIFICATION, AND PRESER- 
VATION OF NEGATIVE. 
Wuew the development is completed, the plate 
is to be washed and placed in the “ fixing bath,” 
which consists of a strong solution of hyposulphite 
of soda. The effect of this is to render the film 
transparent in those parts not acted upon by the 
light, which, previous to this operation, were 
opaque and of a grayish-white color. The plate 
should remain in the “hypo” just long enough 
to clear it up, and should then be thoroughly 
washed. 
In warm climates, and during the summer 
months in northern latitudes, the dry plates of 
some manufacturers require to be washed with 
iced water, to prevent the film from peeling off — 
“ frilling.” At San Francisco, where the summer 
temperature rarely exceeds 70° Fahr., I have not 
found it necessary to resort to the use of iced 
water, and the manufacturer (Hastman) of the 
plates which I have been using advertises plates 
especially prepared for use in tropical climates, 
which he claims will not frill when washed with 
water at the ordinary temperature of that found in 
the tropics. 
A strong solution of common alum is sometimes 
used before or after fixing, to harden the film and 
cause it to dry more quickly. The writer has not 
found it necessary to use it in connection with the 
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