Scientific American Supplement, No. 365, December 30, 1882Various
Science
Scientific American Supplement, No. 365, December 30, 1882
Various
Science -- Periodicals
It is expected that further analysis will be made, this time of the
flour made from the different grades of wheat. If these investigations
be properly conducted, we have no doubt that they will simply confirm
the evidence of the wheat tests. A chemical analysis alone, however,
will not be sufficient. The quantity of flour obtained from a given
amount of wheat must also be ascertained and its quality further tested
by means best known to millers, as regards "doughing-up," keeping
qualities, color, etc. And then the result can be no less than to show
what millers already knew--that the best quality of flour, commanding
the top prices in the market, cannot be obtained from an inferior
quality of wheat.--_Milling World._
* * * * *
APPARATUS FOR PRINTING BY THE BLUE PROCESS.[1]
[Footnote 1: Read June 21, 1882, before the Boston Society of
Civil Engineers.]
By CHANNING WHITAKER.
The blue process is well known to the members of the society, and I need
not take time to describe it; but with the ordinary blue process
printing frame the results are sometimes unsatisfactory, and now that
the process has come to be so commonly used I have thought that an
account of an inexpensive but efficient printing frame would be of
interest. The essential parts of the apparatus are its frame, its glass,
its pad or cushion, its clamps, and the mechanism by which the surface
of the glass can easily be made to take a position that is square with
the direction of the sun's rays.
_The Blue Process Printing Frame in Common Use.--Its Defects._--The pad
of the apparatus in common use consists of several thicknesses of
blanketing stretched upon a back board. The sensitized paper and the
negative are placed between the pad and the plate glass, and the whole
is squeezed together by pressure applied at the periphery of the glass
and of the back-board. Both the glass and the back-board spring under
the pressure, and it results that the sensitized paper is not so
severely pressed against the negative near the center of the glass as it
is near the edges. If at any point the sensitized paper is not pressed
hard up against the negative, a bluish tinge will appear where a white
line or surface was expected. With an efficient printing frame and
suitable negatives, these blue lines will never appear, and it was to
prevent the production of defective work that I undertook to improve the
pad of the printing frame.
Public-domain text, read in full here on John Shaqi.
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