Scientific American, Vol. XXXIX.No. 6. [New Series.], August 10, 1878 — John Shaqi
Scientific American, Vol. XXXIX.No. 6. [New Series.], August 10, 1878Various
Science
Scientific American, Vol. XXXIX.No. 6. [New Series.], August 10, 1878
Various
Science -- Periodicals; Technology -- Periodicals
The iron from a charge of 75 kilos. of pig may be divided with advantage
into a couple of balls; a third may be made of the iron separated from
the walls of the pot. To get out the balls the pot is lowered, and the
workmen use tongs, pointed rabble, and hooked bar. If things have gone
well the balls ought to come out soft at a welding heat, filled with
cinder like puddled balls, but a little more resisting and solid under
the hammer. They are forged into bars, and these are at once passed to
the rolls. If nothing hinders the balling and shingling, these
operations will not consume more than fifteen minutes.
* * * * *
=Photographic Engraving.=
Scamoni's process is as follows: The original drawings are carefully
touched up, so that the whites are as pure and the blacks as intense as
possible, and then the negative is taken in the ordinary way, the plate
being backed in the camera with damp red blotting paper, to prevent
reflection from the camera or back of the plate. The negative is
developed in the ordinary manner, intensified by mercuric chloride, and
varnished. A positive picture is taken in the camera, the negative being
carefully screened from any light coming between it and the lens. This
is intensified by pyrogallic acid, and afterward washed with a pure
water to which a little ammonia has been added. It is then immersed in
mercuric chloride for half an hour, and again intensified with
pyrogallic acid. This is repeated several times. When the intensity of
the lines is considerable, the plate is well washed, treated with
potassium iodide, and finally with ammonia, the image successively
appearing yellow, green, brown, and then violet brown. The plate is then
thoroughly drained, and the image is treated successively with a
solution of platinic chloride, auric chloride, ferrous sulphate, and
finally by pyrogallic acid, which has the property of solidifying the
metallic deposits. The metallic relief thus obtained is dried over a
spirit lamp, and covered with an excessively thin varnish. This varnish,
which is evidently a special preparation, retains sufficient tackiness
to hold powdered graphite on its surface (the bronze powder now used may
be employed instead), which is dusted on in the usual manner. After
giving the plate a border of wax, it is placed in an electrotyping bath,
and a perfect facsimile in intaglio is obtained, from which prints may
be taken in a printing press.
* * * * *
=A NEW DEEP SEA THERMOMETER.=
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account