With regard to Mr.
Watson Smith's observation as to fractional dyeing, he (Mr. Siebold)
did not regard this method as a suitable trial for ascertaining the
strength of an extract, but he admitted it was occasionally very
valuable for detecting an admixture of extracts of other dyewoods,
such as quercitron bark extract in logwood extract. It was also a good
method of ascertaining the speed of dyeing and hence the relative
proportion of fully developed coloring matter of an extract.--_Jour.
Soc. Chem. Industry._
* * * * *
ORTHOCHROMATIC PHOTOGRAPHY.[1]
[Footnote 1: Read before the Photographic Association of
Brooklyn.]
By OSCAR O. LITZKOW.
What I want to show is the manner in which the process has been
tested. My employer, Mr. Bierstadt, has given me permission to show
you some samples, and also his chart containing the spectrum colors:
violet, indigo blue, green, yellow, orange, red, and black. This chart
has been photographed in the orthochromatic and also in the ordinary
way.
There are many ways of producing an orthochromatic effect; one is the
use of a glass tank placed behind or in front of the lens, in which a
coloring matter from either a vegetable or mineral product is placed;
this tank or cell is, however, only for use in the studio, as for
outdoor photography we have a colored glass screen, so as not to be
bothered with carrying colored solution.
Pages:
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93