IMPROVEMENTS RELATING TO THE PRODUCTION OF MOULDS IN WAX, PLASTER OF PARIS, AND OTHER SIMILAR MATERIALS AND PATTERNS, AND OTHER ARTICLES OF INDIA-RUBBER OR OTHER GUM CAPABLE OF VULCANIZATION
Year: 1876

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine, Lake,
& Co., Patent Agents, Southampton Buildings, London, for the Invention of
'IMPROVEMENTS RELATING TO THE PRODUCTION OF MOULDS IN WAX, PLASTER
OF PARIS, AND OTHER SIMILAR MATERIALS AND PATTERNS, AND OTHER
ARTICLES OF INDIA-RUBBER OR OTHER GUM CAPABLE OF VULCANIZATION."
A communication from abroad by Charles Grasser, of Somerville, Massachusetts,
United States of America.
Sealed the 15th December 1876, and dated the 16th June 1876.
PROVISIONAL SPECIFICATION left by the said William Robert Lake at the
Office of the Commissioners of Patents on the 16th June 1876.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS RELATING TO THE PRODUCTION
OF MOULDS IN WAX, PLASTER OF PARIS, AND OTHER SIMILAR MATERIALS AND
PATTERNS, AND OTHER ARTICLES OF INDIA-RUBBER OR OTHER GUM CAPABLE OF
VULCANIZATION." A communication.
This Invention consists partly in producing moulds in wax, plaster, or other
inelastic material, for the formation of articles of utility, statuettes, or other works
of art, having undercut or prominent parts, by the use of soft elastic patterns, and
partly in the production or formation of such patterns.
The said patterns are made by preference of soft rubber, formed within a mould
produced froin an original model by the electrotype process by imbedding the said
mould in wax to a selected dividing line, and after preparing the surface with
plumbago, applying the copper deposit to one side of the model and the surface
of the wax bed forming a flange projecting outward from the model, after which
the model is reversed in its bed and a similar deposit is applied to its other side
and to the flange, the mould thus forined being divisible into halves through the
flange. The copper of which this pattern mould is formed is plated on its inner
face with brass and then with tin to protect it from the sulphur in the rubber.
The elastic pattern produced in the above-described mould has a dividing flange
extending outward from the line of division originally selected.
The opposite sides of this flange produce the meeting faces of the two half moulds
which are formed over and by means of the elastic pattern.
Price 10d1

page_text: For some purposes, and where but few moulds have to be made from one pattern,
glue, or gelatine, or printers' roll composition may be used instead of rubber for
the elastic pattern, the surface of the said glue or gelatine pattern being coated
with a solution of rubber in chloroform in order to prevent the water with which
the plaster is mixed from acting on the material of the pattern so as to distort it
or impair the sharpness of its delicate parts. By mixing the plaster with a strong
solution of alum in water instead of with pure water the plaster will be caused to
set so quickly that the coating of the glue or similar elastic pattern may be dispensed
with; but in this case very rapid manipulation is necessary.
A mould of plaster is taken from the elastic pattern by resting the latter in a
supporting half mould approximating to its shape closely without interfering with
its ready insertion and removal. The soft plaster is applied first with a brush,
and then by pouring within a suitable flask. The pattern and the half mould are
then inverted, and the plaster applied in like manner to the other side.
For forming and vulcanizing a pattern or other article of soft rubber within a
metal mould the raw material is applied to the interior of the mould, first in small
fragments so as to fill all the interstices, and then in larger pieces or sheets, an
opening being left to admit to the interior water in which the whole is immersed,
and which receives a heavy pressure to 'force the rubber against the inner surface
of the mould. Heat is then applied by steam in a surrounding chamber and
through the medium of the water and the metal mould to the rubber.
When the pressure is thus applied through the medium of water the mould
containing rubber to be formed and vulcanized is enveloped in a covering of rubber
or other impervious material connected with the hollow body within the mould
so that when the whole is immersed in water the water will pass within the hollow
body to be formed but cannot pass between it and the mould.
For producing articles in hard vulcanite by the agency of steam, heat, and
pressure, the mould is formed of a thin body of plaster within a perforated flask
or outer mould of metal, approximating to the shape of the pattern, so that the
entire mould may have sufficient strength to resist the pressure, and the plaster
of which its inner surface is formed may not be of sufficient thickness to prevent
the conduction of the necessary heat for vulcanizing.
The raw rubber is applied in sheets over an envelope of soft vulcanized rubber
on a hollow core either porous or perforated, which approximates to the shape of
the article to be formed, the envelope preventing the rupture of the raw rubber
by the internal steam pressure. The vulcanizing heat is produced through the
medium of steam applied by means of separate chambers to the exterior of the
mould and to the interior of the material within it, the pressure on the interior
of the material being in excess of that on the exterior of the mould, so as to cause
the material to be forced in close contact with the inner surface of the mould.
The vulcanizing vessel is of peculiar construction, being formed with an inner
chamber in which the mould is placed (or any number of them) and an outer
chamber with which the hollow interior of the mould communicates through a
hollow screw-plug by which the mould is attached to the vulcanizer and by
suitable ducts.
In using soft elastic rubber patterns for forming moulds of wax, paraffine, or
like substance, the said patterns are coated with glycerine and a solution of sal-
ammoniac or other suitable salt to prevent adhesion of the wax to the rubber.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by the
said William Robert Lake in the Great Seal Patent Office on the 15th
December 1876.
WILLIAM ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,
Southampton Buildings, London. "IMPROVEMENTS RELATING TO THE PRODUCTION

page_text: OF MOULDS IN WAX, PLASTER OF PARIS, AND OTHER SIMILAR MATERIALS AND
PATTERNS, AND OTHER ARTICLES OF INDIA-RUBBER OR OTHER GUM CAPABLE OF
VULCANIZATION." A communication from abroad by Charles Grasser, of Somerville,
Massachusetts, United States of America,
This Invention consists in part in producing moulds in plaster or other inelastic
material for the formation of articles of utility, or statuettes, or other works of art
having undercut or prominent parts by the use of soft elastic patterns.
The said pattern is made by preference of soft rubber, formed within a mould
produced from an original model by the electrotype process by imbedding the said
mould in wax to a selected dividing line, and after preparing the surface with
plumbago, applying the copper deposit to one side of the model and the surface
of the wax bed forming a flange projecting outward from the model, after which
the model is reversed in its bed and a similar deposit is applied to its other side
and to the flange, the mould thus formed being divisible into halves through the
flange. The copper of which this pattern mould is formed is plated on its inner
face with brass and then with tin to protect it from the sulphur in the rubber.
The elastic pattern produced in the above-described mould has a dividing flange
extending outward from the line of division originally selected.
The opposite sides of this flange produce the meeting faces of the two half
moulds which are formed over and by means of the elastic pattern.
For some purposes, and where but few moulds have to be made from one pattern,
glue, or gelatine, or printers' roll composition may be used instead of rubber for
the elastic pattern, the surface of the said glue or gelatine pattern being coated
with a solution of rubber in chloroform in order to prevent the water with which
the plaster is mixed from acting on the material of the pattern so as to distort it or
impair the sharpness of its delicate parts. By mixing the plaster with a strong
solution of alum in water instead of with pure water the plaster will be caused
to set so quickly that the coating of the glue or similar elastic pattern may be
dispensed with; but in this case very rapid manipulation is necessary.
A mould of plaster is taken from the elastic pattern by resting the latter in a
supporting half mould approximating to its shape as closely as practicable without
interfering with its ready insertion and removal. The soft plaster is applied first
with a brush, and then by pouring within a suitable flask. The pattern and the
half mould are then inverted, and the plaster applied in like manner to the other
side.
For forming and vulcanizing a pattern or other article of soft rubber within a
metal mould the raw material is applied to the interior of the mould, first in small
fragments so as to fill all the interstices, and then in larger pieces or sheets, an
opening being left to admit to the interior water in which the whole is immersed,
and which receives a heavy pressure to force the rubber against the inner surface
of the mould. Heat is then applied by steam in a surrounding chamber and
through the medium of the water and the metal mould to the rubber.
When the pressure is thus applied through the medium of water, the mould
containing rubber to be formed and vulcanized is enveloped in a covering of rubber
or other impervious material connected with the hollow body within the mould so
that when the whole is immersed in water the water will pass within the hollow
body to be formed but cannot pass between it and the mould.
For producing articles in hard vulcanite by the agency of steam, heat, and
pressure, the mould is formed of a thin body of plaster within a perforated flask
or outer mould of metal, approximating to the shape of the pattern, so that the
entire mould may have sufficient strength to resist the pressure, and the plaster of
which its inner surface is formed may not be of sufficient thickness to prevent the
conduction of the necessary heat for vulcanizing.
The raw rubber is applied in sheets over an envelope of soft vulcanized rubber
on a hollow core either porous or perforated, which approximates to the shape of
the article to be formed, the cnvelope preventing the rupture of the raw rubber

page_text: by the internal steam pressure. The vulcanizing heat is produced through the
medium of steam applied by means of separate chambers to the exterior of the
mould and to the interior of the material within it, the pressure on the interior
of the material being in excess of that on the exterior of the mould, so as to cause
the material to be forced in close contact with the inner surface of the mould.
The vulcanizing vessel is of peculiar construction, being formed with an inner
chamber in which the mould is placed (or any number of them) and an outer
chamber with which the hollow interior of the mould communicates through a
hollow screw-plug by which the mould is attached to the vulcanizer and by suitable
ducts.
In using soft elastic rubber patterns for forming moulds of wax, paraffine, or like
substance, the said patterns are coated with glycerine and a solution of sal ammoniac
or other suitable salt to prevent adhesion of the wax to the rubber.
hollow screw-plug by which the mould is attached to the vulcanizer and by suitable
ducts.
In using soft elastic rubber patterns for forming moulds of wax, paraffine, or like
substance, the said patterns are coated with glycerine and a solution of sal ammoniac
or other suitable salt to prevent adhesion of the wax to the rubber.
DESCRIPTION OF THE DRAWINGS.
Figure 1 represents a front view of a bust to be made, and of which a metal
mould is to be produced, in which the elastic pattern is to be formed. Figure 2
represents a side elevation of said bust imbedded half in wax to a certain line of
division, as herein-after described. Figure 3 is a front view of said Figure and
wax bed.
Figure 4 represents a section of a metal mould formed from the original pattern,
enveloped in an impervious sack and containing a hollow body of rubber to be
formed into an elastic pattern or other article within said mould, as herein-after
described.
Figure 5 represents a front view of the elastic pattern with the parting flange
formed by the manipulation of forming the pattern in the metal mould, as herein-
after described. Figure 6 is a side view of the elastic pattern and flange.
Figure 7 is a plan view of the support mould in which the elastic pattern is laid
during the process of making moulds. Figure 8 is an end view of the support
inould.
Figure 9 is a front elevation of the elastic pattern resting in the support mould.
Figure 10 is an internal elevation, partly in section, of one half of the flask used
to hold the plaster mould. Figure 11 is a side view of such half of a metal flask.
Figure 12 represents a half flask with the plaster mould formed in it, ready to
receive the core surrounded by the clastic envelope and rubber which forms the
ultimate figure or bust.
Figure 13 represents a vertical section of a core, thimble, pipe, and elastic
envelope, as herein-after described.
Figure 14 is a vertical section of the vulcanizing vessel when used for vulcanizing
the elastic rubber pattern under water.
Figure 15 is a longitudinal section of a vulcanizing vessel used to produce hard
rubber articles.
Figure 16 represents in elevation a half metal flask and plaster mould contained
therein with attaching screw-plug, steam duct, and thimble, and in section the
hollow core and the rubber envelope, and body of raw rubber, which are to form
the finished product.
Figure 17 represents a vertical section of a complete closed flask and mould of
the description used to form a bas-relief.
The original pattern or model is made in boxwood, ivory, or such like material,
or it may be made of metal melting at a low temperature for reasons clearly seen
hereafter. It is hardly necessary to state that the original pattern ought to be
made as perfect as possible, as upon its perfection depends the perfection of the
copy in elastic rubber. The first thing to be done with the original pattern is to
produce a mould from it in metal. This may be done best and most cheaply by
means of the electrotype process. It is necessary to make a mould of a figure in
two parts; to do this the original model is imbedded in wax to a selected line of

page_text: division. The wax bed is made even and smooth horizontally from the line of
division, and may extend two inches, more or less, horizontally from the figure, as it
is represented in Figure 2. When this is done, the model and upper surface of the
wax bed are prepared in the well known manner for taking a copper deposit by
means of the electrotype process. As soon as the copper deposit is about as thick
as a card, the wax bed is removed and the other side of the figure is prepared for
and receives a like deposit, including the flange formed by the deposit on the surface
of the wax bed; after which the deposit of copper is continued all over until a
thickness of about th of an inch is obtained. This produces a mould which is of
sufficient strength to part without injury, the centre of the flange formed by the
alternate deposit being the point of parting. On account of the many undercut
and projecting parts and places of the model there is but one way of its removal
from the mould, which is by destroying the model with fire. If of wood it is burnt
out, if of metal it must be melted. The copper mould formed over the model will
resist such heat without injury. After the mould is parted in the manner indicated,
and all remaining particles of the model are carefully cleaned out, the copper mould
receives a coating
or plating of brass by means of the electrotype process, which is
followed by another coat or plating of tin by the same process. The coat or plating
of tin inust be made as heavy as the mould will bear without injury to the sharpness
or perfection of the same. Said plating of the mould with tin is of great importance
and must be applied with great care. The coating or plating with brass and tin are
for the purpose of protecting the copper mould against the injurious action of the
sulphur in the rubber, as it is well known by rubber manufacturers that copper and
brass moulds cannot be used to vulcanize or cure rubber in them, but if a copper
mould is properly plated with brass and then with a heavy plating of tin it is found
to answer very well and produce the best results. Excepting the plating of the
copper mould in the manner and for the purpose stated there is nothing new in
the production of a copper mould from a figure in the manner described, and it may
be done by any one skilled in the art of electrotyping, and it is described only to
give a correct understanding of the entire manipulation by which the elastic pattern
is produced.
When the copper mould is made and prepared as stated it is ready to receive the
rubber for the elastic pattern, as shown in Figure 4, I being the mould and P the
rubber therein. The rubber to be used must be of pure caoutchouc mixed with a
required quantity of sulphur to make soft elastic rubber. In order to produce a
perfect pattern the process is as follows:-First a thin coat of soap water or a cont
of flexible collodion is applied to the surface of the mould. This coating is for the
purpose of preventing the rubber's adhesion to the mould after the process of curing..
When such coating is dry a thin coating of a solution of raw rubber in benzine is
applied so as to obtain a sticky or adhesive surface on the mould. When such
coating of rubber solution is dry the rubber is introduced in each half mould in this
inanner. Small and suitable pieces of rubber cut from a thin sheet are carefully
laid into all the small cavities of the mould, each being firmly pressed to the mould
to which it will adhere. Care must be taken to prevent the confinement of air in
any of the cavities, which if it takes place will prevent a perfect impression. When
all the cavities are filled, larger pieces of rubber may be used until the whole interior
surface of the mould including the inner surface of the flange is covered with a
uniform thick layer. The first layer is followed by a second and third one, cach
being laid and pressed on carefully. For a pattern of small size the several layers
of rubber need not be thicker than th of an inch. For large patterns greater
thickness is required for imparting the necessary stability to the pattern.
When both half moulds are laid out with rubber in the manner stated they are
carefully jointed and pressed together by the flanges i so much as to squeeze the
rubber P partly out between the flanges, after which both halves are fastened
together with some small screws through the flanges.
At some convenient place, as at E', a small hole of about 1/2 inch is left in the
mould for the purpose of introducing water to the inside of the rubber body, the

page_text: object of which will be seen hereafter. After joining the two halves of the mould
as stated a layer of rubber K is applied to the outside of the mould. Such outside
layer must make a perfect and good connection with the rubber P at the edge of
the flanges and over the edges of the small hole E¹ in the mould with the rubber
at the inside of the mould in close contact. The rubber forming the elastic pattern
or article will only take and retain a perfect impression of the mould, by pressure
applied during the whole process of curing it. The application of such necessary
and uniform pressure to an irregular shape can only be effected by immersing the
whole under water confined in the interior vessel of the vulcanizing apparatus
under a pressure of about 80 lbs. to the square inch. Therefore it is self-evident
that great care should be taken to leave no spot in the layers and joints of the
several pieces of rubber through which the water could reach the inner metal
surface of the mould, which if it took place would prevent a sharp and perfect
impression of the rubber in the mould. To guard against such an emergency the
outside layer of rubber K is applied and a secure union is made between this outside
layer and the rubber between the flanges and over the edge of the hole or opening E¹
used for the admission of water to the interior of the rubber pattern. A connection
is thus made with the rubber forming the pattern. In this manner the metal
mould is fully and completely, surrounded or enveloped in rubber, leaving no chance
for the water to come between the metal surface of the mould and the rubber
except by a carelessly made joint in the rubber.
When the mould has received the rubber in the manner described the whole is
placed in the inside of a vulcanizing vessel, made on the plan represented in
Figure 14, where two such prepared moulds are shown at Y, Y². The cover D is
firmly closed and water is admitted (entering the interior of the bodies within the
moulds through apertures E¹) and is forced into the vessel through the pipe C until
a pressure of about 80 lbs. to the square inch is reached. By means of this pressure
the rubber is firmly pressed into every line and cavity of the mould, and is so kept
during the whole time of curing. The heat required to cure the rubber is produced
by admitting steam to the space A through tho pipe B. The degree of heat as
well as length of time are regulated according to the mixture and quality of the
rubber used and are well known. To avoid blistering of the rubber or changing
shape after curing and while still hot the pressure of the water has to be kept on
until the whole is cooled. When perfectly cooled the mould is removed and the
elastic pattern may be taken from the mould, which is done by cutting the outside
layer of rubber K from the edge of the flange i and mouth of the hole E¹ and by
a gradual and careful parting of the copper mould.
The clastic rubber pattern
may thus be drawn out and is ready for use. This elastic pattern is a perfect
impression of the mould and a true copy of the original model. By means of the
layers of rubber placed between the flanges of the mould a rubber flange P is formed
all around the pattern dividing the pattern into halves on a suitable line at the
place of the joint, as seen by the Drawing, Figures 5 and 6. This rubber flange on
the pattern is of great importance and has to serve the useful purpose of forming
the base and parting partition of the wax or plaster moulds to be taken from the
pattern. Furthermore it serves to keep the pattern in equal shape of contour or
outline on the place of parting and jointing the half moulds, a matter of great
importance as it is highly essential that the moulds taken from the pattern shall
join well at the meeting edges or outline of the mould.
A pattern or model made of soft and elastic rubber is very easily pressed out of
shape and distorted even by a light weight. To avoid this support moulds are
provided. These are made and used in the following manner :-First, the elastic
pattern is laid on moist moulding sand, bringing it in the proper shape and position
to imbed it in the sand in the same manner as was done with the original model in
the wax, care being taken to have the flange P of the elastic pattern in its normal
position resting on the margin on the lower half of the flask or frame containing
the sand. This done, a metal frame or flask F of sufficient size and depth is placed
over the figure or pattern, the lower edge of the frame resting on the flange P.

page_text: Plaster of Paris is then applied carefully in every cavity of the pattern by means of
a small brush, after which the frame is filled with plaster to the edge of the frame,
and even therewith. When the plaster has hardened the whole is turned over, and
another frame like the one used first is placed over the other side of the pattern in
the same manner as foundry men use their flasks in moulding from a pattern, and
the plaster is applied and finished off in the way first described.
When the plaster is hardened the mould so formed is carefully parted. The
rubber pattern will admit of doing this, as it is a very yielding and elastic body
compared with hardened plaster. These first made moulds are used for permanent
supports of the elastic pattern. In order to make further operations more easily
understood they will be called the first half support mould, and second half support
mould. The elastic pattern, although it is one body, will be called the half pattern
P¹, and the half pattern P. The support moulds are then made to admit of an easy
replacing of the rubber pattern P¹, P, which is done by cutting out the projections
in the support moulds, care being taken to preserve the edge or contour of the
mould at the joint line. This being done moulds can be made for regular use either
in wax or plaster of Paris.
If wax or such like substance is melted and cast on india-rubber it will stick to
the same more or less. To remove it by force would injure the wax mould as well
as the pattern, therefore a naked rubber pattern would be of no use for making
wax moulds. To overcome this great obstacle a coating is applied to the rubber
pattern of such a nature as to prevent any sticking or adhesion of the wax to the
rubber, at the same time it will permit a perfect and sharp cast, and does not impair
the sharpest line of the pattern. After a long series of experiments it was found
that a solution of salts, especially sal ammoniac mixed with glycerine would answer,
as such a coating to entire satisfaction. Such mixture is made in about the follow-
ing proportions:-In a gill of water is dissolved one ounce of sal ammoniac, to which
is added half a gill of glycerine. This mixture is applied with a brush to the
surface of the pattern, carefully covering every part. In a short time the water in
the mixture will evaporate, leaving a moist and very uniform coating of glycerine
on the pattern. It is well known how antagonistic glycerine is to a greasy or
resinous substance, and also that it will not evaporate even under the influence of
a higher temperature than the melting point of wax. Of these properties good use
is made in the present Invention. Glycerine alone or mixed with pure water or
even with alcohol will not spread uniformly on a surface where the least greasy
matter exists.
As soon as the water or alcohol has evaporated the glycerine will gather in
minute drops, in consequence of which numerous spots on the pattern would
remain unprotected, to which the wax' will stick. To produce a uniform and
perfect coating of the pattern, as is required, it was found necessary to use a
mixture of salts, water, and glycerine.
After preparing the rubber pattern in the manner stated, the half pattern P¹ is
placed in the first half support mould F, then a metal flask or frame F, similar to
those used for the support moulds, is placed over the pattern, resting it on the
rubber flange and making a good joint to prevent the escape of the fluid wax, after
which the wax is slowly poured over the pattern until the frame or flask is full.
The temperature of the melted wax should not exceed that of boiling water, but
cannot be much below if a perfect sharp mould is to be obtained. When the wax
has become cold the rubber pattern may be easily withdrawn from the wax mould,
as the rubber pattern will stretch and yield easily, thereby relieving readily all the
under cut and projecting parts of the mould. The other half of the pattern is
moulded on in the same manner by placing the half pattern P2 in the second half
support mould, which is the counterpart of the support mould F, and then fol-
lowing out the same manipulations described.
It is not necessary to describe the further preparation of a wax mould to deposit
the copper as it is well known.
Articles of the shape of a figure, or a pot, or a vase are most cheaply and

page_text: practically reproduced by the electrotype process by making them in two halves,
and uniting the halves by soldering.
To take a mould by the present Invention from an article in the shape of a disc
or bas-relief, no matter how many sharp under cuts or projections in the ornamen-
tation may be presented, is an easy matter compared with the labor required to
make a mould in gutta percha of the simplest thing.
The making of a plaster mould from a rubber pattern is done in about the same
manner, with few alterations required by the different nature of the plaster, or
according to the uses for which such plaster moulds may be intended.
If the plaster mould is to be used for the forination of a round body, such as a
figure, pot, vase, and the like, which is closed on all sides, or to be ornamented on
all sides, and such an article is to come from the mould as a whole and not in
halves or parts, it will be necessary that the frame or flask used to hold the plaster
shall be so arranged that all the flasks or frames to be used are provided with
steady pins and are interchangeable with each other for the purpose of making a
perfect joint or match of the outline or contour of the article moulded. The use of
the support mould will bring the pattern at all times in the same position relatively
to the steady pins of the flask.
In taking a plaster of Paris mould from a rubber pattern, a solution of soap in
water is applied with a brush to the pattern as a coating to prevent the adhesion
of the plaster. After this a thin layer of plaster of Paris is applied to the pattern,
carefully introducing the same in every cavity, and then filling the frame, making
it even on the top.
Other substances may be used to make moulds from a rubber pattern besides
wax and plaster, for instance, paraffine mixed with wax is very good composition,
and many other like compositions, but such compositions should not require a
higher temperature to render them perfectly fluid and melted than that of boiling
water, which is all the rubber pattern will stand without injury.
Moulds made of wax and such like material are best adapted for use in the
electrotype process, while plaster moulds are useful for a great variety of things,
such as casting in soft metals, also for casting and forming articles from the great
variety of fluid and plastic compositions used for the manufacture of different
things.
It is evident that a certain degree of judgment must be exercised on the part
of the operator in applying this Invention in the production of the great variety
of moulds which are required for differently shaped articles. The plane of division
in each article which is to be moulded so as to part the mould with the best
results can be selected by the skilled operator. Persons skilled in the art of
making moulds will quickly comprehend the great advantage of having a pliable
and elastic pattern as this made of india-rubber as herein described.
In making moulds for the manufacture of articles of hard rubber I proceed as
follows: Plaster of Paris is a very poor conductor of heat, therefore, if a plaster
of Paris mould is used to form and cure hard rubber in it is very essential to make
the body of the plaster forming the mould as thin as possible. If the plaster
mould is too thick in body the vulcanizing of hard rubber will be imperfect and
the product worthless. Furthermore, a plaster mould by itself has no strength to.
resist expansive pressure, which is required if a plaster mould is to be used for
forming an article in rubber of such a shape that it cannot be made solid. These
difficulties are completely overcome in the present Invention by the use and
application of a peculiarly made flask or box. Such flasks must be made of strong
metal, and in all cases must approximate to the shape of the article to be made in
rubber, but they must be somewhat larger so as to admit of forming a plaster of
Paris lining on the interior. This plaster of Paris lining receives the full and
sharp outlines of a mould taken from the pattern.
Figure 10 in the accompanying Drawings represents an interior face view, and
Figure 11 a side elevation of a half flask. It is provided with a flange P³ for the
purpose of holding two such halves together by means of screws passed through the

page_text: holes R. The body or hollow part of the flask approaches to the shape of the figure
selected for illustration, and is perforated with small holes 8 to serve as vents for the
air in the plaster mould. At U is a funnel-shaped pipe or opening for the intro-
duction of the plaster when the flask is closed on the pattern. It is further necessary
that all flasks used for a similar article be made and arranged in such a manner as
to fit each other and be interchangeable.
In making plaster moulds for regular use to form india-rubber articles the process
is as follows:- The elastic pattern receives first a coating with soap water to prevent
the adhesion of small particles from the plaster mould, after which the half pattern
P¹ is placed in the first half support mould F¹¹. Then the plaster is applied by
means of a small brush in every cavity of the pattern and all over the same until
a uniform layer of plaster is all over the pattern, then a flask, such as above
described, is placed over the pattern, resting on the rubber flange in such a manner
that the gate print C¹ on the pattern corresponds and fits to opening C on the
flask. This done the remaining space in the flask is filled with plaster through
the funnel-shaped pipe U, the small perforations 8 being previously closed with
wooden pegs.
When the plaster is hardened the support mould is removed, and
then the elastic pattern is readily drawn from the mould, the other side of the
pattern is then moulded by placing the half pattern P2 in the second half support
mould and following the same manipulations as before.
As the flasks used are all interchangeable with each other, and are likewise so
with the support mould flasks by means of steady pins p, all moulds so formed will
join perfectly as the use of a support mould made, arranged, and used in the manner
stated, will invariably place the rubber pattern in the same position to all the flasks
used.
To form india-rubber in a mould requires considerable pressure, which has to
be kept up until the rubber is cured. Therefore metal moulds are mostly used on
account of their strength and conductability of heat, and plaster moulds have been
only used to make such articles of rubber as could be formed in the plaster moulds
by pressure applied laterally to a flat surface. Hence the common mode of using
plaster moulds does not involve special difficulties, but in order to form of rubber a
perfect article in the shape of a clock case, figure, bust, door-knob, cane handle,
vase, and the great variety of articles of forms which present many undercut and
projecting parts, requires manipulations altogether different from those used at
present in the manufacture of rubber goods.
On account of the fragile nature of plaster it is impossible to press a body of
rubber in such mould as it is done with metal moulds, depending on the great
pressure to force the surplus rubber out between the joints; but it is necessary to
get this rubber into an approximate shape first, and to place it in the mould with
proper care and judgment, to use as little rubber as possible, consistently with the
required strength of the article. Furthermore, means must be provided to make
the operation of giving the rubber its ultimate shape a certainty, so as not to
produce more imperfect than perfect articles. The objects are effectually accom-
plished by proceeding as follows:-After the plaster mould is made in the manner
described, a plaster of Paris core is made which is so much smaller than the cavity
of the mould that if it was placed in the mould a space of about ths of an inch
would remain between the core and the interior of the mould. Such core is made
from a special mould for the purpose in the same manner as foundry men form
cores for hollow castings.
Figure 13 of the Drawings represents a vertical section of a core such as is required
for a figure given as an illustration. A² is the plaster core, and c indicates an
elastic rubber envelope of the said core, the purpose of which will be seen hereafter;
a tube E is connected with the core during the making or forming of the same.
At the outside end of the tube E and slipped over the same is a funnel-shaped
thimble B made of soft pliable metal. It will also be noticed that the elastic
envelope c comes nearly to the edge of the wider end of the thimble, indicating that
the rubber envelope surrounds not only the core but part of the tube E and the

page_text: outside of the thimble B2, the utility of which will be seen hereafter. This elastic
envelope of the core is made as follows:-As soon as the plaster core is formed with
the tube attached to it, it is made dry and free from moisture, after which a coat of
rubber solution is applied to give the core an adhesive surface, after this a layer of
rubber mixed in such a manner as to make soft and elastic rubber after curing is
laid on.
This layer of rubber is applied all round the core so as to form a perfect
air-tight envelope over the same, including so much of the tube E and thimble B²
as indicated above. This done the core so enveloped or any number of such cores
are placed in a common vulcanizing vessel to cure the rubber envelope. When this
is done the core is ready for further use. The core has a shape approximating to
that of the article to be made, and the next thing to be done is to apply such a
thickness of raw rubber to this core as will admit of placing it in the plaster mould.
The application of the raw rubber to the core is best done by cutting strips from a
sheet of rubber about inch wide, and ths of an inch thick, and wrapping then
uniformly round the core on the elastic envelope until a required thickness is
obtained. Each layer ought to be well pressed on to make a united mass of the
whole. The mixture of the rubber applied on the core and envelope has to be
according to the quality of the article wanted either soft, semi-hard, or hard rubber.
After charging the core with the required quantity of rubber it is placed in the
plaster moulds which have received previously a coating of flexible collodion to
prevent the adhesion of the plaster to the rubber article after curing the rubber.
When the core is laid in one half of the mould in such a manner that the tube E
with the thimble B2 fills the gate in the mould and flask the other half mould is
placed over it and both halves are firmly screwed together by the flanges of the
flasks, the screw plug C is screwed in the boss T against the thimble B2, which will
spread and pack the rubber envelope or rather that part of it lying against the
outside of the thimble firmly and air-tight within the taper Hole in the base of the
flask.
Figure 16 of the Drawings represent a vertical section of a mould so charged
and will clearly illustrate it. F is the metal flask, and c¹ the plaster lining forming
the perfect mould; A2 is the plaster core; c is the elastic envelope; A³, the rubber
which is to form the ultimate product; E, the tube connected with the core; B², the
metal thimble; C, the screw-plug; G, a jam nut.
The pressure required to force the rubber into every cavity of the mould and
take a perfect impression of the same is produced by connecting the charged mould
by the projecting end of the screw plug C2 with a corresponding screw coupling
in the bottom of the inner vessel of the vulcanizing apparatus, as represented in
Figure 15. Any number of charged moulds may be attached in the same
manner, according to the capacity of the vessel. After charging the vessel and
the steam cover steam is gradually admitted to the space A. through the pipe B,
closing the will also enter through the hole in the screw plug 02 and reaches
by the tubo E the centre of the plaster core A², finding its way through the
pores of the plaster, and acting on the inside of the elastic rubber envelope c
will expand the same, which expansion will cause a uniform pressure on the
irregular surface of the rubber A³ pressing it into every outline of the mould.
The importance of the elastic envelope c will now be apparent, as it forms, so
to say, the packing, preventing the steam from coming in direct contact with
the plaster mould during the important process of imparting the sharp impression
to the rubber. If the steam were allowed to act directly against the raw rubber
it would usually tear it, as raw rubber becomes very soft when heated and is
not an elastic and tough material as when cold or vulcanized. The sharp pro-
jections of a mould would cut it at some point and the least broken spot would
allow the steam to reach the plaster mould and prevent a perfect impression, such
a break is effectually prevented by the use of an elastic tough envelope or cover
which has been made so by a previous curing process. The pressure of the steam
in the space A, and on the inside of the mould is raised to about 45 lbs. to the
square inch, and is kept so for about 30 minutes during which time the rubber

page_text: becomes fully softened and receives a full impression of the mould; but such
heat of steam at a pressure of 45 lbs. is not sufficient to make hard rubber, so it is
gradually increased to about 85 lbs., but it has been found that even such a pressure
and the consequent increase of heat would not produce a good hard rubber as long
as it acted only on the inside of the mould, besides that it would cause too great
a strain on the flasks enclosing the plaster mould therefore steam is also admitted
to the inner vessel through a pipe or valve C, but the pressure is limited to 70 lbs.
to the square inch on the exterior of the flask. By so doing the required heat is
obtained to make a good quality of hard rubber. This variable and unequal
pressure is of great importance as it is found to be the only way to obtain a perfect
sharp impression of the mould with a reproduction of as smooth a surface as the
mould presented.
The higher pressure on the inside of the mould keeps the rubber in close contact
with the mould, thereby preserving the full impression, as rubber is a very pliable
and yielding substance while under such temperature, even when it is cured for
hard rubber. It has been found that if the pressure were equally high on the
outside of the mould, even after the process of curing was in an advanced state,
the surface of the article presented a porous and rough surface, and in many cases a
disfiguration of the article. Therefore, the principle of having a lower pressure on
the outside of the mould is of great importance if a perfect article is to be obtained.
The time of curing rubber in this manner is about thus, 45 to 50 lbs. steam for 30
minutes on the inside of the mould alone gradually increased to 85 lbs. per square
inch with a corresponding lower pressure of 70 lbs. per square inch on the outside
of the mould or flask for two hours, which makes an aggregate time of 2 hours
30 minutes. This is for hard rubber. Soft rubber is regulated according to the
mixture.
After the process of vulcanizing in the manner stated the moulds are removed
and the articles may be taken from the moulds. The plaster core has become soft
and is readily removed by washing it out. The elastic envelope has become incor-
porated with the rubber, forming the article and becomes part of the same.
The foregoing description gives a full illustration of the mode of operation in the
making of such articles as figures, clock cases, vases, caskets, and the like, where
the article presents a closed or full body, and although the manipulations remain
the same in principle a saving of time may be effected in the making of flat-
shaped things, such as bas-relief or a dish, presenting but one side to be finished or
ornamented. The elastic pattern for moulding such an article is made on the
same principle as described.
Similar moulds and a corresponding flask is used; but as such flask has a flat or
dish-shape it is not necessary to use two half flasks, as a simple plate provided
with a boss for the screw plug and connections will answer, also the plaster core
may be dispensed with, and in cases where the design of the article presents no
great projections or deep cavities the elastic covering may be dispensed with, as the
raw rubber will admit of some stretching on a flat-shaped surface.
Figure 17 represents a flask charged with rubber ready for connection.
F is the flask; C₁, the plaster mould formed in the flask; H is the rubber ex-
tending over and squeezed between the flanges of the flasks and cover; F" is the
cover to the flask with the boss T in the centre in which is a simple screw; C° with
a hole C, said screw is for the connection to the vulcanizer, and the hole C for the
admission of the steam. In all other essential things the manipulations remain the
same.
A. description will now be given of the mode of making a perfect plaster mould
from a pattern or model made of gelatine, glue, or printers' roll composition. It is
found that bone glue is the best for this purpose. It is well known that plaster of
Paris casts have been made out of glue moulds, but such casts are more or less im-
perfect, the water in the plaster will swell and soften the glue, and the plaster will
adhere to it, so that while a plaster cast made on glue presents a rough soft surface
fine and sharp outlines are mostly lost all these defects would make a plaster mould

page_text: taken from glue patterns worthless for the purpose, although they may be good for
other purposes for which they are used at present. By pursuing a series of experi-
ments remedies have been found for such defects, so that glue patterns may be used
for making plaster moulds, answering the purpose in cases where a limited number
of copies may 'he wanted. By applying a coating of a solution of caoutchouc in
chloroform to a glue pattern two or three perfect sharp plaster moulds may be
taken from it, or by the use of a strong solution of alum in water mixed with the
plaster in place of water the same result may be obtained, the latter is, however,
more difficult to use as the plaster sets almost too quickly even for a swift work-
man. Glue patterus may be cast in a metal mould such as used for making elastic
rubber pattern; a glue pattern should have a similar parting flange as a rubber
pattern.
+
In selecting the line of division for the formation of the two part pattern moulds
by the preliminary process first described careful regard is liad to the best plane or
planes of parting to facilitate drawing the elastic pattern from the final moulds, and
with reference also to the introduction of the core charged with rubber if the final
moulds are to be used for the manufacture of hard rubber articles.
Having thus fully described the said Invention, as communicated to me by my
foreign correspondent, and the manner of performning the same, I wish it understood
that I claim-
First. The process of producing an inelastic mould by means of an elastic soft
pattern, as above described.
Second. The mode or process of preparing a pattern of glue, gelatine, or analogous
material for forming moulds of plaster or other like material, as above described.
Third. A soft or elastic pattern constructed with a parting flange, as and for the
purposes set forth.
Fourth. The process of making a mould by the use of a soft or elastic pattern
provided with a dividing flange to form the parting surface of each half mould, as
above described.
Fifth. The process of taking a mould or impression from a soft or elastic pattern
with the aid of a support mould, as above set forth.
Sixth. A flask approximating to the shape of the article to be formed in
combination with a mould of plaster or analogous material, as above set forth.
Seventh. The process of forming patterns or other articles of soft rubber within
suitable moulds by means of internal pressure of water or other inelastic fluid,
applied as above set forth.
Eighth. The process of applying pressure through the medium of water or other
non-elastic fluid surrounding the mould and introduced to the interior of the
rubber to force it in contact with the mould, as above described.
Ninth. An impervious envelope or sack applied over the mould to prevent
access between the surface of the mould and the material to be moulded of liquid
employed as the pressure inedium in the formation of soft rubber patterns or other
articles.
Tenth. The mode or process of applying pressure through the medium of water
or other non-elastic fluid to force the material into contact with the mould while
heat is conducted through the said pressure liquid to vulcanize the material, as
above set forth.
Eleventh. A coating of glycerine and a salt solution or equivalent material ap-
plied to a soft rubber pattern for making moulds in wax, paraffine, or similar
substance.
Twelfth. A core employed in the production of india-rubber goods for the support
and preliminary shaping of the rubber, as above set forth.
Thirteenth. The combination with a core of an envelope of vulcanized rubber
or equivalent material to prevent the rupture of the raw rubber by internal pressure.
Fourteenth. The process of approximately shaping an article of india-rubber
by applying the material to an internal support and subsequently applying an
•

page_text: expanding pressure to force the material into contact with the interior of the
mould.
Fifteenth. The process of applying an internal steam pressure in excess of the
pressure on the outside of the article to be vulcanized, as above set forth.
Sixteenth. A vulcanizing vessel or apparatus constituted as herein described.
Seventeenth. The combination of the flask, plaster mould, thimble, tube, and
screw plug, as and for the purposes set forth.
.
In witness whereof, I, the said William Robert Lake, have hereunto set my
hand and seal, this Fifteenth day of December, in the year of our Lord
One thousand eight hundred and seventy-six.
.