IMPROVEMENTS IN TEMPERING GLASS, AND APPARATUS FOR THAT PURPOSE
Year: 1877

page_text: In the Matter of Letters Patent granted to William Frederick Mason, of
Heath Bank, Heaton Chapel, in the County of Lancaster, for the
Invention of "IMPROVEMENTS IN TEMPERING GLASS, AND APPARATUS
FOR THAT PURPOSE." Partly a communication from abroad by Frederick
Siemens, of Dresden, in the German Empire, bearing date the Twenty-
eighth day of April 1877, No. 1657.
DISCLAIMER AND MEMORANDUM OF ALTERATION as proposed to be
entered by Frederick Siemens, of Dresden, in the German Empire, pursuant to
the Statutes in that case made and provided.
WHEREAS Her Majesty, Queen Victoria, by Her Letters Patent, under the
Great Seal of the United Kingdom of Great Britain and Ireland, bearing date at
Westminster, the Twenty eighth day of April 1877, in the fortieth year of Her
reign, did give and grant unto the said William Frederick Mason, his executors,
administrators, and assigns, the sole privilege, for the term of fourteen years thence
next ensuing, of making, using, exercising, and vending within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle of Man,
the said Invention of "IMPROVEMENTS in TEMPERING GLASS, AND APPARATUS FOR
THAT PURPOSE." Partly a communication from abroad by Frederick Siemens, of
Dresden, in the German Empire: And whereas in pursuance of a proviso in the
said Letters Patent contained the said William Frederick Mason did within six
calendar months next after the date of the said Letters Patent cause a Specification
or instrument in writing under his hand and seal purporting to describe and
ascertain the nature of the said Invention, and in what manner the same was to
be performed, to be duly filed in the Great Seal Patent Office:
And whereas the said Letters Patent were assigned to and became and now are
the property of me the said Frederick Siemens:
And whereas I, the said Frederick Siemens, have ascertained that some of the
claiming clauses of the said Specification may be objected to on the ground that
the matters claimed therein are not such as, after the publication of the Specification

page_text: to my previous Letters Patent, dated the 3rd day of May 1875, No. 1637, could be
considered altogether novel in 1877, and I have no desire to retain any claim in
respect of these matters.
I therefore disclaim and alter the said Specification in manner following, that is
to Bay -
Referring to the Queen's Printer's copy of the said Specification, at page 3,
lines 5 and 6, I omit " according to the present Invention;" at page 3, line 12,
after "referred to" I insert "as having been described in the Specification of.
F. Siemens' Patent, dated the 3rd May 1875, No. 1637;" at page 3, line 13, I
omit "First. The method of;" I omit the second, third, and fourth claims; that
is to say, in page 3, lines 17 to 26 inclusive.
And the said Specification when so disclaimed, altered, and amended, will read
In the Specification to Letters Patent granted to F. Siemens on the ora may
1875, No. 1637, was described a process of tempering and pressing glass by
subjecting it while in a heated condition to pressure between heated moulds or
plates.
In carrying this process into practice it has been found that certain improve-
ments in the method of operating are desirable for ensuring perfect success and
the highest obtainable resistance to fracture in the product.
In order to effect the hardening of the glass with safety and diminish the
chances of fracture, particularly when glass sheets of large dimensions are operated
upon, it has been found that it is advisable to modify the nature of the surfaces of
the pressing moulds, or to prepare them in a peculiar manner according to the
thickness and size of the glass to be operated upon, and also according to its
physical qualities and composition.
In order to obviate too sudden a cooling it is necessary to prevent the immediate
contact of the glass operated on with the surfaces of the pressing moulds themselves.
For this purpose I interpose between the pressing moulds and the glass a sheet or
layer of suitable material of a pliable nature, which can perfectly assume the
configuration of the glass articles, and isolates it to a certain extent from the
pressing mould.
I employ for this purpose, according to the nature and com-
position of the glass, either a thin sheet of perforated metal or fine wire gauze of
any suitable metal, or a sheet of textile fabric, such as cloth, canvas, paper, &c.; or
again, a finely pulverized substance, such as plaster of Paris, talc, or soapstone, &c.;
or, lastly, a substance in a state of solution applied in the form of a varnish or
coating, either on the glass itself or on the pressing moulds.
When an energetic cooling requires to be effected, the glass is only separated
from the pressing moulds by a single thickness of metal tissue or other substance,
or by a thin coating of the above mentioned substances. If, on the other hand, it
be desired that the cooling shall take place slowly, two or more thicknesses of
tissue, or a thicker coating of the material is used.
In all cases the nature of the tissue or the coating of material used should vary
with the desired rapidity and energy of the cooling, and with the nature and
composition of the glass.
It is sometimes advisable, in order to prevent the warping or getting out of shape
of the glass articles, to apply to the surface of the glass a layer or sheet of one
description of the before mentioned materials, while between this and the surface
of the mould is interposed a layer or sheet of material of a different description.
Thus, for example, for operating on curved glass I place upon the glass a coating
of plaster of Paris, while upon the surface of the mould I place a coating or sheet
of wire gauze. Thus by the careful choice of the tissues or substances interposed
or by the combination of the various means above indicated, it is easy in each case
to obtain a perfectly suitable cooling for every form and description of the glass

page_text: operated upon.
Practice has proved that this process presents great advantages
both as regards a considerable reduction of the breakages during and after the
operation, and as regards the intensity and uniformity of the hardening. The
influence of this process is strikingly shown by the fact that it is only by this
means that the fibrous fracture can be imparted to thick glass which generally
characterizes the glass treated according to F. Siemens' hardening process.
It has been found during the process of manufacture that the use of pressing
moulds cooled artificially is very advantageous; such moulds can thus be maintained
at a uniform temperature and be used for a much greater length of time without
being changed. I employ for such cooling, according to the nature of the article
to be cooled, either water, steam, vapour, or gas at a suitable temperature. For
this purpose open hollow moulds containing water may be used as described in
F. Siemens' before mentioned Patent, but by preference closed hollow moulds are
employed, through which water or other liquid at a temperature below 212° Fahr.,
is made to circulate, the moulds being for this purpose connected by flexible or
jointed pipes to a receptacle containing the water or other liquid.
Having thus described the nature of the said Invention, and in what manner
the same is to be performed, I claim in respect of the process of hardening,
tempering, and pressing glass hereinbefore referred to as having been described in
the Specification to F. Siemens' Patent, dated the 3rd May, 1875, No. 1637.
Interposing between the articles to be operated upon and the pressing mould one
or more sheets, layers, or coatings of a substance or substances that will retard or
modify the action of the metal upon the article to be treated.
In witness whereof, I, the said William Frederick Mason, have hereunto
set my hand and seal, this Twentieth day of September, in the year of our
Lord One thousand eight hundred and seventy seven.
W. F. MASON. (L.S.)
In witness whereof I the onid Frederick Siemana have hereunto act
To the Commissioners of Patents for Inventions.
I hereby grant my fiat, giving leave to the above named Frederick Siemens (as
Assignee of the said Letters Patent) to file in the Office of the Commissioners of
Patents for Inventions, with the Specification to which the same relates, the above
written Disclaimer and Memorandum of Alteration.
I hereby grant my fiat, giving leave to the above named Frederick Siemens (as
Assignee of the said Letters Patent) to file in the Office of the Commissioners of
Patents for Inventions, with the Specification to which the same relates, the above
written Disclaimer and Memorandum of Alteration.

page_text: LETTERS PATENT to William Frederick Mason, of Heath Bank, Heaton Chapel,
in the County of Lancaster, for the Invention of "IMPROVEMENTS IN TEMPERING
GLASS, AND APPARATUS FOR THAT PURPOSE." Partly a communication from
abroad by Frederick Siemens, of Dresden, in the German Empire.
PROVISIONAL SPECIFICATION left by the said William Frederick Mason at
the Office of the Commissioners of Patents on the 28th April 1877.
WILLIAM FREDERICK MASON, of Heath Bank, Heaton Chapel, in the County of
Lancaster. "IMPROVEMENTS IN TEMPERING GLASS, AND APPARATUS FOR THAT
PURPOSE." Partly a communication from abroad by Frederick Siemens, of Dresden,
in the German Empire.
In the Specification to Letters Patent granted to F. Siemens on the 3rd May 1875,
No. 1637, was described a process of tempering and pressing glass by subjecting it
while in a heated condition to pressure between heated moulds or plates.
According to the present Invention the heating of the moulds is dispensed with,
the tempering of glass being effected by the use of cold moulds faced with material,
such as wire gauze or fireproofed fabric, which is interposed between the surface of
the mould and that of the glass.
In order to secure uniformity of temper in the glass operated on, the moulds are
uniformly cooled by the circulation through them of cold air or liqud, for which
purpose they are made hollow with suitable partitions to determine the flow of the
cooling fluid over the whole body of the mould; or jets of cold fluid may be made to
play on the backs of the moulds for the same purpose.
In cases were the glass operated on has projections and hollows on its surface, as
in ribbed glass, several thicknesses of the facing material or fabric are employed, so
that it may give to the irregularities of the surface and permit the tempering to be
effected uniformly.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Frederick Mason in the Great Seal Patent Office on the
26th October 1877.
WILLIAM FREDERICK MASON, of Heath Bank, Heaton Chapel, in the County of
Lancaster. "IMPROVEMENTS IN TEMPERING GLASS AND APPARATUS FOR THAT
PURPOSE." Partly a communication from abroad by Frederick Siemens, of Dresden,
in the German Empire.
In the Specification to Letters Patent granted to F. Siemens on the 3rd May 1875,
No. 1637, was described a process of tempering and pressing glass by subjecting it
while in a heated condition to pressure between heated moulds or plates.
In carrying this process into practice it has been found that certain improvements
in the method of operating are desirable for ensuring perfect success and the highest
obtainable resistance to fracture in the product...
In order to effect the hardening of the glass with safety and diminish the chances
of fracture, particularly when glass sheets of large dimensions are operated upon, it
has been found that it is advisable to modify the nature of the surfaces of the
pressing moulds, or to prepare them in a peculiar manner, according to the thick-
ness and size of the glass to be operated upon, and, also according to its physical
qualities and composition.
In order to obviate too sudden a cooling it is necessary to prevent the immediate
contact of the glass operated on with the surfaces of the pressing moulds themselves.
For this purpose I interpose between the pressing moulds and the glass a sheet or
layer of suitable material of a pliable nature, which can perfectly assume the
configuration of the glass articles, and isolates it to a certain extent from the
pressing mould. I employ for this purpose, according to the nature and composition
of the glass, either a thin sheet of perforated metal, or fine wire gauze of any suitable
metal, or a sheet of textile fabric, such as cloth, canvas, paper, &c., or again, a finely
pulverized substance such as plaster of Paris, talc, or soapstone, &c; or lastly, a
substance in a state of solution applied in the form of a varnish or coating either on
the glass itself or on the pressing moulds.
When an energetic cooling requires to be effected the glass is only separated from
the pressing moulds by a single thickness of metal tissue or other substance, or by
a thin coating of the above-mentioned substances. If on the other hand it be
desired that the cooling shall take place slowly, two or more thicknesses of tissue
or a thicker coating of the material is used.
In all cases the nature of the tissue or the coating of material used should vary
with the desired rapidity and energy of the cooling and with the nature and com-
position of the glass.
It is sometimes advisable, in order to provent the warping or getting out of shape
of the glass articles, to apply to the surface of the glass a layer or sheet of one
description of the before-mentioned materials, while between this and the surface of
the mould is interposed a layer or sheet of material of a different description. Thus
for example, for operating on curved glass, I place upon the glass a coating of plaster
of Paris, while upon the surface of the mould I place a coating or sheet of wire
gauze. Thus by the careful choice of the tissues or substances interposed, or by the
combination of the various means above indicated, it is easy in each case to obtain a
perfectly suitable cooling for every form and description of the glass operated upon.
Practice has proved that this process presents great advantages, both as regards a
considerable reduction of the breakages during and after the operation, and as
regards the intensity and uniformity of the hardening. The influence of this process
is strikingly shewn by the fact that it is only by this means that the fibrous
fracture can be imparted to thick glass, which generally characterises the glass
treated according to F. Siemens' hardening process.
It has been found during the process of manufacture that the use of pressing
moulds cooled artificially is very advantageous; such moulds can thus be maintained

page_text: at a uniform temperature and be used for a much greater length of time without
being changed. I employ for such cooling, according to the nature of the article to
be cooled, either water, steam, vapour, or gas at a suitable temperature. For this
purpose open hollow moulds containing water may be used as described in
F. Siemens' before-mentioned Patent, but by preference, according to the present
Invention, closed hollow moulds are employed, through which water or other liquid
at a temperature below 212° Fahr. is made to circulate, the moulds being for this
purpose connected by flexible or jointed pipes to a receptacle containing the water
or other liquid.
Having thus described the nature of the said Invention, and in what manner the
same is to be performed, I claim in respect of the process of hardening, tempering,
and pressing glass, herein-before referred to,-
First. The method of interposing between the articles to be operated upon and
the pressing mould one or more sheets, layers, or coatings, of a substance or
substances that will retard or modify the action of the mould upon the article to be
treated.
Second. The use of a pressing mould having its inner surface covered by one
or more sheets, layers, or coatings, of a substance or combination of substances
that will retard or modify the action of the mould upon the article to which it is
applied.
Third. The use of a pressing mould maintained at a temperature below that of
the boiling point of water, that is to say, below 212° Fahr., substantially as herein
described.
Fourth. The use of a hollow pressing mould maintained at a constant temper-
ature by the circulation through it of water or other liquid, substantially as herein
described.
In witness whereof, I, the said William Frederick Mason, have hereunto set my
hand and seal, this Twentieth day of September, in the year of our Lord
One thousand eight hundred and seventy-seven.
W. F. MASON. (L.S.)