Improvements in the Manufacture of Sound-recording Materials for Graphophones.
Year: 1898

page_text: Date of Application, 23rd Apr., 1898-Accepted, 4th June, 1898
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Sound-recording Materials for
Graphophones.
I, GEORGE WILLIAM JOHNSON, of 47, Lincoln's Inn Fields, in the County of London,
Patent Agent, do hereby declare the nature of this invention (which has been
communicated to me from abroad by the American Graphophone Company, a
Corporation organized under the laws of West Virginia, and with its principal office
at Washington, District of Columbia, in the United States of America), and in what
manner the same is to be performed, to be particularly described and ascertained in
and by the following statement :—
This invention relates to the manufacture of tablets or blanks adapted to receive
engraved records of sounds, and more particularly to the composition of matter of
which the tablet or blank is composed.
The recording material, in order to answer well the requirements of the engraving
method of recording sounds, should be perfectly amorphous, slightly cohesive, and
capable of being removed cleanly and smoothly in chips, or shavings, under the
action of the recording stylus when actuated by the feeble force of sound waves.
The material moreover should be sufficiently hard to withstand ordinary handling, to
retain perfectly its form, and to resist the effect of ordinary changes of temperature.
It should also be a stable compound; or material, in order that records made in it
may be preserved for indefinite lengths of time.
The properties above indicated reside in greater, or less, degree in wax, and wax-
like substances, such as beeswax, paraffin, stearine, and the like, though, by special
preparation of these and similar substances, their fitness for the purpose in view has
been increased.
It has been heretofore proposed to use as a sound recording material an insoluble
soap made by saponification of any fatty acid by means of an earthy alkali, such as
lime. It has also been proposed to employ a metal such as lead, combined with
stearic, or oleic, acid, and particularly a mixture of oleate and stearate of lead. But
tablets made of insoluble lime soap, or of stearates, or oleates, of lead have never
yielded commercially successful results. Several practical difficulties have been
encountered in endeavouring to make tablets or blanks composed wholly, or in part,
of soap. The chief difficulty has been that the surfaces of such tablets or blanks
become coated, after a greater, or less, length of time, with a bluish film having the
appearance of mould, and which has been termned "efflorescence." This is due to the
presence in the material of hygroscopic compounds, which, on being attacked by
moisture work out to, and spread upon, the surface of the tablet or blank.
My foreign correspondents have found that lead in any form, as well as most of the
salts of other metals which might be otherwise suitable for the purpose in view, give
rise to the hygroscopic compounds. This is particularly true of stearates and acetates
of lead.

page_text: Another difficulty that arises is the formation of crystalline, or crystallizable,
compounds in the operation of making soap. The object of introducing a metal
(or metallic salt) is to prevent all tendency to crystallization, it being of the first
importance to secure a composition which shall be, and under all conditions remains
perfectly amorphous, and which presents equal resistance to cutting in every
direction. All ordinary commercial soaps have this tendency to crystallization in
some degree, it not being possible to introduce sufficient sodium, or soda salt, to
prevent all crystallization.
In carrying out the present invention, whereby all the conditions herein pointed
out as essential are secured, stearic acid is taken as nearly pure as can be obtained,
and is converted into soda soap in the manner hereafter explained. The composition,
however, differs from ordinary soap in, that it contains no oleates, it having been
found that the presence of even a small quantity of oleate, or oleic acid, is
detrimental. It is also important that the tallow, or other source from which the
stearic acid is obtained, be completely deglycerinized. Except under these conditions
the result will be unsatisfactory..
In converting the stearic acid into soap only a partial saponification is produced,
that is to say, instead of using the chemical equivalent in caustic alkali of the fat
acid, about forty per cent. of that quantity of alkali is used, thus producing what
may be called a soap of about two-fifths saponification. This is the proportion which
gives the best results, but is of course variable within limits. The controlling
consideration is that the greater the quantity of alkali, the higher will be the melting
point of the resulting soap, and a complete saponification will produce a soap which
requires to melt it a temperature which will char it. As the material is to be inoulded
into cylindrical or other forms, it must be capable of melting at a moderate
temperature (say between 250° and 330° Fahrenheit). On the other hand, if the
saponification be not carried far enough, the material will be too soft and will run at
a lower temperature than is desired. In this soap aluminium is incorporated, which
iny foreign correspondents have found to be the metal best suited in all respects for
the purpose.
This may be used in the form of aluminic hydrate or in the metallic
state, powdered, or in small ingots. The method of introducing the metal is
moreover important, owing to the tendency of sodium and aluminium when combined
to form crystallizable compounds. Preferably the metal is first incorporated in the
soda lye, forming with a portion thereof aluminate of soda (sodium-ortho-aluminate
NaAlO) which readily unites with the stearic acid subsequently added.
quantity of aluminium employed is relatively very small.
The
In order that the invention may be fully understood I will give two formulas which
have yielded the best results obtained.
Stearic acid (free from oleic acid and glycerine)
Aluminic hydrate
Caustic soda lye
408 lbs.
7 lbs.
85 lbs.
To this is added, for the purpose of "tempering," paraffin, ozokerite, or similar
material 72 lbs.
The caustic soda is incorporated in water until a lye of 37.50 B. is obtained, and
this is heated to its boiling point, about 242° Fahrenheit. The aluminic hydrate is
added and is quickly incorporated in the lye. The stearic acid is melted and raised
to about the same temperature and the lye added slowly thereto. It will unite readily
therewith. It is preferred to employ about the temperature indicated, as thereby the
formation of the composition proceeds gradually and without violent ebullition. The
temperature may subsequently be raised to about 300° Fahrenheit and continued at
that heat until the water is all expelled. The composition is now completed except
for the addition of a material such as paraffin, ozokerite, or ceresin, to bring it to the
desired degree of hardness.

page_text: Ceresin
OU TOS.
The sal soda lye and caustic soda lye may be united before the aluminium is added,
or the latter may be added to the caustic soda, and the two liquids then united.
Instead of powdered aluminium ordinary ingot aluminium may be used with results
nearly, if not equally, as good.
After the material is moulded to the desired form it should be quickly cooled to
ordinary temperatures.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The process of making a sound-recording material by dissolving aluminium in
soda lye, and adding the solution to stearic acid substantially as herein before
described.
2. The process of making a sound-recording material by melting stearic acid; free
from glycerine and oleates, adding thereto soda lye and aluminium, and heating the
mass, substantially as hereinbefore described.
3. In the process of making a sound-recording material, the improvement
consisting in adding to stearic acid soda lye in which a metal such as aluminium has
been incorporated in such quantity as to produce partial saponification, and heating
the mixture, substantially as hereinbefore described.
4. The process of making a graplophone tablet or blank by forming a soda lye,
heating it to about its boiling point, dissolving a small quantity of aluminium
therein, heating pure stearic acid to about the same temperature, adding the solution,
continuing the heating until the moisture is expelled, moulding into the desired
shape and then quickly cooling substantially as herein before described.
5. The process of making a sound-recording material, by dissolving aluminium in
a soda lye, adding it to stearic acid, heating the mixture, and adding a softening
material such as paraffin substantially as hereinbefore described.
Dated thin 02nd day of dil 1000
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.