IMPROVEMENTS IN THE MANUFACTURE OF WHITE, OPAQUE, OPALESCENT OR SEMITRANSPARENT GLASS AND ENAMEL
Year: 1884

page_text: I JOHN HENRY JOHNSON of 47 Lincolns Inn Fields in the County of Middlesex
Gentleman do hereby declare the nature of said Invention for "IMPROVEMENTS IN
THE MANUFACTURE OF WHITE, OPAQUE, OPALESCENT OR SEMITRANSPARENT GLASS
AND ENAMEL which Invention has been communicated to me from abroad by
Adolf Teodesco of Mügeln, near Pirna, Kingdom of Saxony German Empire, to be
as follows:-
"
Instead of using Phosphate of lime or Cryolite, or felspar or fluor-spar or the
double fluoride of aluminium and alkali in conjunction with and in addition to the
ordinary mixtures used in the manufacture of glass, in order to produce, white
opaque opalescent or semi-transparent glass there is used according to this In-
vention for the said purpose the fluoride of an alkali together with a substance
containing alumina-The use of an alkaline fluoride and of a substance containing
alumina for the said purpose will afford essential advantages compared with the
use of the above named double fluoride of aluminium and alkali for the said
purpose.
It is well known that the production of the double fluoride of aluminium and
alkali is a difficult one inasmuch as its production will require the employment of
vessels made of special material such as platina, in order to resist the action of the
agents employed, whereas the manufacture or production of an alkaline fluoride is
comparatively a simple one especially if alkali be taken or maintained in excess 80
that the corrosive action of the fluoric acid is counteracted.
The excess of alkali which characterises the product (for use in conjunction with
the ordinary mixture for producing glass) being an admixture of an alkaline
fluoride with an alkaline carbonate is of no disadvantage on the contrary this
excess may be calculated as a part of the quantity of alkali, which forms part of
the ordinary glass mixture.
I may point out as an especially important feature. of this Invention that by
the use of an alkaline fluoride and a substance containing alumina the addition of

page_text: alumina to the glass mixture can be accurately determined and varied which is not
the case in using double fluoride of aluminium and alkali as in this compound the
proportion of alumina is a determined or specific one.
The quantity of alumina has to be in accordance with the quality of glass to be
produced, therefore in employing an alkaline fluoride and a substance containing
alumina separately according to this Invention the alumina may be varied at will
according to the quality or degree of opacity of the glass to be produced.
The alkaline fluoride may be manufactured by neutralizing caustic soda, or
caustic potash or carbonate of soda or carbonate of potash with fluoric acid, taking
care to have a surplus of alkali. The product of this neutralization is then
evaporated and calcined.
As a substance containing alumina it is proposed to use hydrate of alumina,
China clay or the like.
The alkaline fluoride and the body containing alumina are either mixed together
and afterwards added to the ingredients for the production of glass or the said
alkaline fluoride and the body containing alumina are added separately to said
mixture.
The quantity of alkaline fluoride to be added will depend upon the degree of
transparency which the glass is to have and the proportion of the substance
containing alumina will as hereinbefore stated be varied either according to the
quality of the glass to be produced or according to the amount of alumina present
in the ingredients forming the glass mixture.
The following way of producing the fluoride of alkali may also be adopted-The
aluminate of an alkali is treated with fluoric acid until all the alkali is fixed so
that hydrate of alumina will precipitato After calcination of the compound an
admixture of alkaline fluoride and alumina will be the result.
The production of this admixture is very simple indeed, inasmuch as there are
only neutral combinations and the corrosive action of the fluoric acid has no effect.
The admixture of an alkaline fluoride and of alumina is mixed with the
ingredients for the production.of glass.
In the same manner the alkaline fluoride and alumina may be used in the
production of enamel such as is used for enamelling metal or the like. It will be
understood that colouring materials may be added according to the colour of
enamel to be produced.
Unted the 28th day of April 1881

page_text: "
I JOHN HENRY JOHNSON of 47 Lincolns Inn Fields, in the County of Middlesex,
Gentleman, do hereby declare the nature of this invention for "IMPROVEMENTS IN
THE MANUFACTURE OF WHITE OPAQUE, OPALESCENT, OR SEMITRANSPARENT GLASS
AND ENAMEL which invention has been communicated to me from abroad by
Adolph Tedesco of Mügeln near Pirna Kingdom of Saxony German Empire and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
Instead of using Phosphate of lime or Cryolite or felspar or fluor-spar or the
double fluoride of aluminium and alkali in conjunction with and in addition to the
ordinary ingredients or mixtures used in the manufacture of glass in order to
produco white opaque opalescent or semitransparent glass, there is used according to
this Invention for the said purpose, the fluoride of an alkali (or alkaline fluoride)
either with or without the conjoint.use of a substance containing alumina. The
uso of an alkaline fluoride for the said purpose will afford essential advantages
compared with the use of the abovenamed double fluoride of aluminium and alkali
for the said purpose.
It is well known that the production of the double fluoride of aluminium and
alkali is difficult, inasmuch as its production will require the employment of vessels
made of special material such as platina, in order to resist the action of the agents
employed, whereas the manufacture or production of an alkaline fluoride is com-
paratively simple especially if alkali be taken or maintained in excess, so that the
corrosive action of the flouric acid is counteracted.-The excess of alkali which
characterises the product, (for the use in conjunction with the ordinary ingredients
or mixture for producing glass) being an admixture of an alkaline fluoride with an
alkaline carbonate, is of no disadvantage, on the contrary this excess may be
calculated as a part of the quantity of alkali which forms part of the ordinary
glass mixture or ingredients.
I may point out as an especially important feature of this Invention that by the
use of an alkaline fluoride the amount of alumina to be added to the glass mixturo,
can be accurately determined and varied, which is not the case in using double
fluoride of aluminium and alkali, as in this compound the proportion of alumina is
a determined or specific onc.
The alkaline fluoride may be manufactured by neutralizing caustic soda, or
caustic potash, or carbonate of soda, or carbonate of potash with fluoric acid, taking
care to have a surplus of alkali.-The product of this neutralization is then
evaporated and calcined.
Another mode of manufacturing the alkaline fluoride, consists in treating
aluminate of alkali with fluoric acid till all the alkali is fixed, so that hydrate of
alumina is precipitated and after culcination a mixture of alkaline fluoride and
alumina will result. This mode of manufacture is very simple and suitable,
inasmuch as there are only neutral combinations no destructive or corrosive action
of the fluoric acid can take place.
The quantity of alkaline fluoride to be added will depend upon the degree of
transparency which the glass is to have.
The following is an example of the way in which alkaline fluoride may be used
according to this invention for the making of opaque glass, compared with an
example of the ordinary use of cryolite as hereinbefore mentioned. The following

page_text: is one of the proportions of mixture frequently used for the production of opaque
glass with cryolite.
25 parts of cryolite
25
"
"
soda, 98 to 100 %
10
170
chalk
"
"
sand
"
Now with an alkaline fluoride, containing 90 %% of fluoride and 10% of soda,
an opaque glass of a character equal to that obtained from the above mixture with
Cryolite, will be produced by mixing about-
38 parts of fluoride of alkali of the above specified composition
150
sand
"
">
The addition of china clay in this instance in the proportion specified, or in
similar proportion, is for the purpose of producing a glass equal to that produced by
the above mixture with cryolite.
•
In view of the fact, that the alkaline fluoride contains more alkali than the
cryolite, the addition of soda to the glass mixture, may be materially reduced, as
is clearly seen by comparing the figures of the above examples.
The alkaline Huoride is mixed with the glass. producing substances either before
or during the melting of the same.
Although I have specified above, two different ways of producing the alkaline
fluoride, I wish it to be clearly understood, that I do not limit myself to either of
these ways for obtaining the alkaline fluoride, nor to any other way of obtaining
the same, as the main feature of this invention consists in an addition of alkaline
fluoride to a mixture of substances for producing glass, it being immaterial whether
the alkaline fluoride be obtained by the above specified processes or by any other
process.
In the same manner the alkaline fluoride and alumina may be used in the
production of an enamel such as is suitable for use for enamelling metal or the like-
It will be understood that colouring materials may be added according to the colour
of enamel to be produced.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is
The production of white opaque, opalescent, or semitransparent glass, or of
enamel, by the employment of an alkaline fluoride in conjunction with
materials employed for the production of glass or enamel in the manner, and
for the purpose substantially as hereinbefore described.