Scientific American Supplement, No. 384, May 12, 1883Various
Science
Scientific American Supplement, No. 384, May 12, 1883
Various
Science -- Periodicals
The precipitated emulsion is now taken into the dark room and washed
until the wash water shows no trace of color; if there be a large
quantity, this is best done on a fine muslin filter; if a small
quantity, by decantation.
Having been thoroughly washed, I dissolve the pellicle in water by
immersing the beaker containing it in the water bath. I then add the
remaining gelatine, and make up the whole with 3 ounces of alcohol and
water to 30 ounces for the quantities given. I pass the emulsion through
a funnel containing a pellet of cotton wool in order to filter it, and
it is ready for coating the plates.
To coat a plate, I place it on this small block of leveled wood, and
pour on down a glass rod a small quantity of the emulsion, and by means
of the rod held horizontally, spread it over the plate. I then transfer
the plate to this leveled slab of plate glass, in order that the
emulsion on it may set. As soon as set, it is placed in the drying box.
This process, as here described, does not give plates of the highest
degree of sensitiveness, to attain which a further operation is
necessary; they are, however, of exceedingly good quality, and very
suitable for landscape work.--_Photo. News_.
* * * * *
PICTURES ON GLASS.
The invention of M. E. Godard, of Paris, has for its object the
reproduction of images and drawings, by means of vitrifiable colors on
glass, wood, stone, on canvas or paper prepared for oil-painting and on
other substances having polished surfaces, e. g., earthenware, copper,
etc. The original drawings or images should be well executed, and drawn
on white, or preferably bluish paper, similar to paper used for ordinary
drawings. In the patterns for glass painting, by this process, the place
to be occupied is marked by the lead, before cutting the glass to suit
the various shades which compose the color of a panel, as is usually
done in this kind of work; the operation changes only when the glass
cutter hands these sheets over to the man who undertakes the painting.
The sheets of glass are cut according to the lines of the drawing, and
after being well cleaned, they are placed on the paper on the places for
which they have been cut out. If the window to be stained is of large
size and consists of several panels, only one panel is proceeded with
at a time. The glass is laid on the reverse side of the paper (the side
opposite to the drawing), the latter having been made transparent by
saturating it with petroleum. This operation also serves to fix the
outlines of the drawing more distinctly, and to give more vigor to the
dark tone of the paper. When the paper is thus prepared, and the sheets
of glass each in its place, they are coated by means of a brush with
a sensitizing solution on the side which comes into contact with the
paper. This coating should be as thin and as uniform as possible on
the surface of the glass. For more perfectly equalizing the coating, a
second brush is used.
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