This done, and
the gelatine set, the plate is immersed in alcohol for a few minutes
in order to remove the greater part of the water from the gelatinous
stratum. The next step is to allow the plate to remain for five or six
minutes in a cold mixture of one part of sulphuric acid with twelve
parts of water, and in the mean time two parts of sodium fluoride are
dissolved in one hundred parts of water, an ebonite tray being used. A
volume of the dilute sulphuric acid equal to about one-fourth of the
fluoride solution is next added from the first dish, and the plate
is then transferred to the second dish, when the film soon becomes
liberated. When this is the case, it is placed once more in the dilute
sulphuric acid. After a few seconds it is rinsed in water, and laid on a
sheet of waxed glass, complete contact being established by means of a
squeegee, and the edges are clamped down by means of strips of wood held
in position by American clips or string. All excess of sulphuric acid
may now be removed by soaking the plate in methylated alcohol, after
which it is dried.
Pages:
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110