IMPROVEMENTS IN ANNEALING GLASS
Year: 1877

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in thé
County of Middlesex, Patent Agent, for the Invention of "IMPROVEMENTS
IN ANNEALING GLASS." A communication from abroad by Le Baron Léon
Edouard Albert, and Jules Marie Augustin Weyer, both of Paris, France.
Dealed the 21st December 1877, and dated the 24th July 1877.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 24th July 1877.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. "IMPROVEMENTS IN ANNEALING GLASS." [A communication from
abroad by Le Baron Léon Edouard Albert and Jules Marie Augustin Weyer, both
of Paris, France.]
This Invention relates to improvements in annealing glass, and consists in burying
or immersing the glass when cold in solid substances reduced to powder, such
as pounded stone, plaster, lime, fire-clay, and others; or in liquids, such as
grease, oil, nitrate of potash, nitrate of soda, and in short any solid or liquid
capable of attaining the degree of heat necessary for the annealing operation.
The object of the process is to render articles of glass stronger and more capable
of sustaining transitions of heat and cold. Ordinary lamp chimneys, for example,
are liable to crack under a considerable variation of temperature, or by a drop of
cold water touching them while hot; but after having been annealed by this process
they may when highly heated be suddenly cooled, and even be immersed in cold
water without danger of cracking. The champagne bottles now used will sustain
a pressure of about 25 to 30 atmospheres only; but if annealed by the process
of this Invention they will support from 40 to 50 atmospheres. The annealing of
glass has been but imperfectly effected heretofore, in consequence of insufficient heat,
as the articles being uncovered the heat could not be raised beyond a certain point
without danger of distorting the articles.

page_text: The improved process comprehends two methods, viz., annealing with pulverized
In using
solid substances, and annealing with liquids as above mentioned.
pulverized solid substances the articles of glass are placed in tire-clay pots or
crucibles, the articles being first filled with and then buried in the pulverized solid
substances, of which there should be a layer at least 2 inches thick above the upper-
most article being treated. The pots or crucibles being thus filled are placed in the
annealing oven, which is constructed like those for annealing bottles generally used
in glass works. The heat is then gradually raised to 800° C., or even 1000° C.,
according to the kind of article to be annealed, this heat being maintained 4 to 6
hours, in order to allow the molecules of the glass to arrange themselves. The
operation requires 24 hours for thick glass, such as bottles and decanters, 16 to 18
hours sufficing for thin goods.
The method of annealing by the use of liquids gives similar results more rapidly
and at less cost. In this case, I employ two boilers, placed one above the other,
in order to run off the liquid from the upper to the lower one. The upper one is
filled with nitrate of soda, nitrate of potash, or a liquid which will support a tem-
perature of 280° C. to 1000° C. As soon as the salts are melted the articles to be
annealed are, when cold, placed therein, and the heat is raised to the highest degree;
the liquid will adınit, say, 800° C., in the case of nitrate of soda. The cooling is
then effected as slowly as possible. The nitrate solidifies at 260° C., but to take out
the glass at this temperature, although well annealed, would impair the operation,
and the liquid is therefore run off into the lower vessel, care being taken to maintain
a small fire beneath the boiler in which the glass still remains. By this means a
complete cooling is slowly effected.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alexander Melville Clark in the Great Seal Patent Office on the 24th
January 1878.
[6
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent.
IMPROVEMENTS IN ANNEALING GLASS." A communication from
abroad by Le Baron Léon Edouard Albert and Jules Marie Augustin Weyer, both of
Paris, France.
This Invention relates to improvements in annealing glass (including crystal
glass), and consists in supporting the glass whilst it is undergoing the annealing
operation by burying or immersing it in solid substances reduced to powder,
such as pounded stone, plaster, line, fire-clay, and others; or in liquids, such as
grease, oil, melted nitrate of potash, or nitrate of soda, and in short any solid
or liquid capable of supporting the degree of heat necessary for the annealing
operation.
The object of the Invention is to enable a higher degree of heat to be attained,
to render the annealing more perfect, and the articles stronger and more capable of
sustaining sudden transitions of heat and cold. Ordinary lamp chimneys, for
example, are liable to be cracked by a considerable variation of teinperature, or by
a drop of cold water touching them while hot; but after having been annealed
by this process, they may when highly heated be suddenly cooled, and even be
plunged in cold water without danger of cracking. Again, the champagne bottles
now used will only sustain a pressure of about 20 to 30 atmospheres; but if
annealed by the process of this Invention, they will be rendered capable of
supporting a pressure of from 40 to 50 atmospheres. The annealing of glass by
the ordinary process has been comparatively imperfect heretofore, in consequence
of the articles being unsupported in the oven, so that the heat could not be raised
beyond a certain point without danger of distortion.
The Invention comprehends two methods, vizt., annealing with pulverised solid
substances, and annealing with liquids, as above mentioned. In using pulverised
solid substances, the articles of glass are placed in fire-clay pots or crucibles, the
articles being first filled with and then buried in the pulverised solid substances,
of which there should be a layer at least 2 inches in thickness above the upper-
most article in the pot or crucible. The pots or crucibles being thus filled, are
placed in the annealing oven, which is constructed like those for annealing bottles
generally used in glass works. The heat is then gradually raised to 800° C., or
even 1000° C., according to the kind of article to be annealed, and maintained for
about 4 to 6 hours, in order to allow the molecules of the glass to arrange themselves.
The operation requires 24 hours for thick glass, such a bottles or decanters; 16 to
18 hours sufficing for thin goods.
The method of annealing by the use of liquids gives similar results more rapidly
and at less cost. In this case, two boilers are employed, placed one above the other,
in order that the liquid may be run off from the upper to the lower one. The
upper boiler is filled with nitrate of soda, nitrate of potash, or a liquid which will
support a temperature of 280° C. to 1000° C. As soon as the salts are melted, the
articles to be annealed are placed therein in a cold state, and the heat is raised to
the highest degree the liquid will adınit, which is 800° C., in the case of nitrate of
soda, and then allowed to cool as slowly as possible. The nitrate, however,
solidifies when cooled down to 260° C., and as the annealing would be impaired if
the glass were taken out at this temperature, the nitrate while still liquid is run off
into the lower vessel, and a small fire maintained beneath the boiler in which the
glass still remains. In this way the glass is completely cooled.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the herein-
before in part recited Letters Patent is,--
The improvements in annealing glass, consisting in burying or immersing the

page_text: glass, in solid substances reduced to powder, or in a liquid capable of supporting the
degree of heat necessary, and in subjecting it when thus buried or immersed to the
annealing operation, substantially as and for the purpose herein specified.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Twenty-second day of January, in the year of our
Lord One thousand eight hundred and seventy-eight.
A. M. CLARK. (L.S.)