Five Mile Beach weekly journal., 1916-01-07
MAKING A RECORD
Methods by Which a Photograph
Disk Is Produced.
CATCHING THE SOUND WAVES.

They Are First Imprisoned In Wax and
Then Transferred to a Negative In
Copper, and From This Master Mold
the Records Are Obtained.
The Edison ~phonograph, the graphic
phone type perfected by Bell and Tain
ter and the gramophone type by Ber-
liner are all based on substantially the
same principle. Sound waves set up in
the air by any sound are allowed to
strike a delicately held diaphragm,
which vibrates under the impact of the
sound waves. The vibrations are made
to leave a record on a suitable me-
dunn, and this sound record is used to
perform the inverse operation when 1t
is required to reproduce recorded
sounds-that is, the record is made to
vibrate a sensitive diaphragm and set
up In the air particular waves, which
convey to the ear the impression of
sound.
The differences in the systems are In
the way in which the vibrations are re-
corded. The disk record, which made
the machine popular, was first manu-
featured in the United States in 1897.
Improvements in the machine and In
the needles followed.
To make a gramophone record a per-
son sings before the mouth of a horn,
the object of which is to concentrate
the energy of the sound waves upon
the recording diaphragm. At the mar
row end of the horn are the recording
sound box and the machine with it's
attendant expert There is a screen
between singer and operator to guard
the secrets of the sound box. On the
farther side of the screen is a hori-
zontal table carrying a wax tablet,
rotated beneath the recording sound
box at a uniform speed. usually about
seventy-six revolutions per minute. As
the table rotates it travels literally at
a uniform speed, and the wax tablet
is thus caused to travel slowly under
the stationary recording box. The
sapphire cutting point is lowered so
as to enter the wax three and one-half
to -four one-thousandths of an inch, and
as the machine runs it cuts a fine spiral
groove. running from the edge to the
center. The construction of the sound
box is secret. as is the composition of
the wax tablet.
The next step in the process is b
reproduction of the record as a mega
tive in copper. The wax is busted with
graphite and worked into the grooves
with a badger brush to make it cleo
tro-conductive; her it is lowered into
an electrolytic bath of copper salt solu-
ton. The wax is kept in continuous
motion in the bath until the copper
shell is nine-tenths of a millimeter In
thickness.
This negative is a master, and from
this a few commercial samples can be
pressed to test the quality of the rec
ord. The manufacturers, however,
wish to make thousands of copies
without hurting their master; there
fore they make duplicates of their
master by taking impressions in wax
composition. from which working mat
rices are made. Then copper shells
are obtained from these in the same
way. The copper shell is then backed
by a brass plate one-half inch In thick
ness by soldering under pressure.
Then the matrix is nickel plated on
the recorded side in order to wear bet
ter and after polishing is ready for
the pressing machine. The commercial
record is pressed into some substance
hard at normal temperature and plastic
under heat and very hard and smooth.
Various compounds are employed by
different makers, but shellac is the
principal ingredient Shellac, wood
charcoal, heavy spar and earthly color
ing matter in certain proportions are
used.
This compound after careful mixing
is rolled into thin sheets and divided
into sections, one for each record. The
section IS then pressed by a hydraulic
press. The matrix is heated and placed
face up in a mold, the label is placed
face down on the matrix, and on this is
placed in a warm, plastic state enough
material for one record. Both halves
of the press are furnished with cooling
plates, through which streams of water
can be passed, and the surfaces are
cooled quickly. The record is then. re-
moved, the edges trimmed with emery
wheels, and it is then ready for SALE
New York Times.