The Bennington evening banner. (Bennington, Vt.) 19??-1961, 1916-01-13
MAKING A RECORD
Methods by Which a Photographs
Disk Is Produced.
CATCHING THE SOUND WAVES.
They Are First Imprisoned In Wax and
Then Transferred to Negative In
Copper, AID From This Master Mold
the Records Are Obtained.


Then Transferred to Negative In
Copper, AID From This Master Mold
the Records Are Obtained.
The Edison phonosraph, the graphic
phone type perfected by Bell and Tain
Ter aud The sramophone type by Ber-
liner are all based ON substantially the
same principle. Sound waves set up in
the air ly any sound are allowed TO
strike "A dclieatCly held diaphragm,
which yibratcs uuler the impact of the
sound waves. The vibrations are made
to laa}e record on suitable me
dunn, aud this sound record is used to
perform the inverse operation when il
is required TO reproduce recorded
sounds-thai is, the record is made to
vibrate Il sensitive diaphragm and set
mp 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 sramophone record per.
son sings before the mouth of 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 ana the machine with lis
attendant expert There is screen
between singer and operator 10 guard
The secrets OF the sound box. On the
farther side OF the screen is a horl-
| Zouia table carrying wax tablet.
| rotated beneath the recording sound
| box ~ = uniform speed. usually about
| seventy six revolutions per minute. AS
the table r0mtes it travels laterally ut
n 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 he wax three and one-half
! TO four one-thOusandthS of an inch, and
as the machine runs it cuts fine spiral
! groove. running from the edge 10 the
| ceRter THE construction of the sound
| box is secret as is the composition Of
The WAX tablet
The next step in the process is the
| reproduction OF the record as a mega
Tive IN copper. The wax is busted with
graphite and worked into the grooves
with q badger brush 10 make it clec-
| tro conductive, thcn it is lowered into
gn e.eeraIytic BATH Of copper salt solu-
ton The wax is kept IN continuous
morion ia the bath until the copper
shell is rine-tenths of millimcter in
thickness
This negative is i master. aud from
this o few commercial samples can he
pressed to test the quality of tue rec.
ord The manufacturers, however,
| wish 10 make thousands or 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 Il hydraulic
press The matriX is heated and placed
face up in 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 lee passed. ana 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.