IMPROVEMENTS IN BAKING OR HARDENING VULCANITE OR . DENTAL INDIA-RUBBER AND OTHER SIMILAR COMPOUNDS AND PREPARATIONS, AND IN APPARATUS EMPLOYED FOR SUCH PURPOSE
Year: 1867

page_text: LETTERS PATENT to Frederick Ryding, of Lower Glentworth Street, in
the County of the City of Limerick, Ireland, Surgeon Dentist, for the
Invention of "IMPROVEMENTS IN BAKING OR HARDENING VULCANITE OR .
DENTAL INDIA-RUBBER AND OTHER SIMILAR COMPOUNDS AND PREPARATIONS, AND
IN APPARATUS EMPLOYED FOR SUCH PURPOSE."
Sealed the 3rd September 1867, and dated the 11th March 1867.
PROVISIONAL SPECIFICATION left by the said Frederick Ryding at the
Office of the Commissioners of Patents, with bis Petition, on the
11th March 1867.
I, FREDERICK RYDING, of Lower Glentworth Street, in the County of the
City of Limerick, Ireland, Surgeon Dentist, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN BAKING OR HARDENING VULCANITE
OR DENTAL INDIA-RUBBER AND OTHER SIMILAR COMPOUNDS AND PREPARATIONS, AND
IN APPARATUS EMPLOYED FOR SUCH PURPOSE," to be as follows:-
. These improvements relate to the baking or hardening of a certain prepa-
ration or compound of india-rubber called vulcanite or dental india-rubber and
such other compounds or preparations of india-rubber or caoutchouc and gutta

page_text: percha as are at present baked or hardened, by the process called vulcanizing
and by means of certain apparatus called vulcanizers.
The Invention consists principally in the mode of applying a dry heat of
any required temperature to every portion of the substance to be worked on
by means of a bath of melted metal. The bath consists of a cauldon (open or
closed) which may be of any shape or size desired, into which is to be put
any metal or alloy of two or more metals, composed in such proportions that
it will melt to about the consistency of butter at the required temperature
without being sufficiently fused to cause evaporation or oxidization of the
metal. The bath containing the alloy is placed over a fire or furnace, and
heated until the metal or alloy becomes sufficiently liquid to allow of the case
containing the rubber or other preparation to be hardened being sunk into it.
The case containing the vulcanite or other preparation in a mould of plaster
of Paris or other suitable substance is then plunged into the bath in precisely
the same state as. it is at present put into vulcanizers now in use.
The case
will in almost every instance be lighter than the melted metal, and, having a
tendency to float, it will require a weight or screw to keep it about an inch
beneath the surface of the metal. The cauldron is then placed over a fire or
gas or other lamp, and kept heated sufficiently to be about the consistency of
butter, not quite fluid, but sufficiently soft to allow of a blunt instrument
being sunk into it without difficulty; if the metal is kept heated beyond
this point it will oxidize and become useless for subsequent operations, but
if not overheated the alloy will be all but indestructible. The work is
allowed to remain in this bath as long as the operator thinks fit, having regard
to its nature. and the object intended. The operator should not allow the
metal to cool as in such a case the work would become fixed, and it would
require extra heating to loosen the work, which might injure or render
the work useless. To prevent explosion by sudden evaporation of steam, the
case containing the vulcanite or other preparation should be thoroughly
dried and freed from all fluid or moisture previously to being put in the bath.
The great difficulty in the various methods at present used of applying a
continual equalized heat- to every portion of the work is thus overcome; the
metal being a good conductor and absorber of heat it is impossible for any
portion of the alloy to become more heated than another, while the slowness
with which it changes temperature renders constant watching unnecessary,
and no thermometer is required; as the softness of the metal is the simplest
and most infallible test of the heat. There is no danger of accidents such as
are at present frequent from the bursting of vulcanizers now in use, and much
time is saved by the process, as a much greater, heat can be applied by this

page_text: mode than by, the baths of steam, saturated steam, subsaturated steam and oil,
as used at present, all of which will burst if heated to a temperature beyond
what they are made to bear (generally two hundred and twelve degrees).
SPECIFICATION in
pursuance of the conditions of the Letters Patent, filed
by the said Frederick Ryding in the Great Seal Patent Office on the
10th September 1867.
...
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FREDERICK
RYDING, of Lower Glentworth Street, in the County of the City of Limerick,
Ireland, Surgeon Dentist, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Eleventh day of March, in the year of our Lord One
thousand eight hundred and sixty-seven, in the thirtieth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Frederick Ryding, Her special licence that I, the said Frederick Ryding,
my executors, administrators, and assigns, or such others as I, the said
Frederick Ryding, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
BAKING OR HARDENING VULCANITE OR DENTAL INDIA-RUBBER, AND OTHER SIMILAR
COMPOUNDS AND PREPARATIONS, AND IN APPARATUS EMPLOYED FOR SUCH PURPOSE,"
upon the condition (amongst others) that I, the said Frederick Ryding,
my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the same
was to be performed, and cause the same to be filed in the Great Seal Patent
Office within six calendar months next and immediately after the date of the
said Letters Patent.
NOW KNOW YE, that I, the said Frederick Ryding, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement in writing, that is to say :-
These improvements relate to the baking or hardening of a certain prepa-
ration or compound of india-rubber called vulcanite or dental india-rubber, and

page_text: such other compounds or preparations of india-rubber or caoutchouc and gutta
percha as are at present baked or hardened by the process called vulcanizing,
and by means of certain apparatus called vulcanizers.
The Invention consists principally in the mode of applying heat of any
required temperature to every portion of the substance to be worked on by
means of a bath of melted metal. The bath consists of a cauldron (open or
closed) which may be of any shape or size desired, into which is to be put any
metal or alloy of two or more metals composed in such proportions that it will
melt to about the consistency of butter at the required temperature without
being sufficiently fused to cause evaporation or oxidization of the metal. The
bath containing the alloy is placed over a fire or furnace and heated until the
metal or alloy becomes sufficiently liquid to allow of the case containing the
rubber or other preparation to be hardened to be sunk into it. The case
containing the vulcanite or other preparation in a mould of plaster of Paris or
other suitable substance is then plunged into the bath in precisely the same
state as it is at present put into vulcanizers now in use. The case will in
almost every instance be lighter than the melted metal, and having a tendency
to float it will require a weight or screw to keep it about an inch beneath the
surface of the metal. The cauldron is then placed over a fire, or gas or other
lamp, and kept heated sufficiently to be about the consistency of butter, not
quite fluid, but sufficiently soft to allow of a blunt instrument being sunk into
it without difficulty; if the metal is kept heated beyond this point it will
oxidize and become useless for subsequent operations, but if not overheated
the alloy will be all but indestructible. The work is allowed to remain in
this bath as long as the operator thinks fit, having regard to its nature and
the object intended. If the operator allows the metal to cool the work will
become fixed and will require extra heating to loosen, which he should cal-
culate on lest he may injure or render the work useless by overbaking. To
prevent explosion by sudden evaporation of steam the case containing the
vulcanite or other preparation should be thoroughly dried and freed from all
fluid or moisture previously to being put in the bath. The great difficulty in
the various methods at present used of applying a continual equalized heat to
every portion of the work is thus overcome; the metal being a good conductor
and absorber of heat it is impossible for any portion of the alloy to become
more heated than another, while the slowness with which it changes tem-
perature renders constant watching unnecessary, and no thermometer is
required by an experienced workman, as the softness of the metal is the
simplest and most infallible test of the heat. There no danger of accidents
such as are at present frequent from the bursting of vulcanizers now in use,

page_text: and much time is saved by the process as a much greater heat can be applied
by this mode than by the baths of steam, saturated steam, subsaturated steam,
and oil, as used at present, all of which will burst if heated to a temperature
beyond what they are made to bear (generally 212°). The great economy.
of this method is another advantage, as alloys can be made which will melt at
any temperature for a trifling cost, no expensive machinery or apparatus is
required, such as the present vulcanizers which contain safety valves, thermo-
meters, screw lids, and other appliances. The saving in fuel is about 75
per. cent., the metal being a great absorber of heat. Any quantity of work
can be done together, the only thing required being a boiler large enough and
a sufficient quantity of alloy. When, from neglect by overheating, one of the
metals used being of a volatile nature, or from any other cause, the operator
finds that the metal does not melt at the heat required he can reduce it to its
former proportions by adding such a portion of the volatile metal as may have
escaped; if he does not understand doing this himself sufficiently it could be
done for him at any foundry at a trifling expence.
The operator can take out his work in the middle of the baking to see if it
is all right, a thing impossible before, and he has the advantage of never
having his work burned in one place while not sufficiently heated in another.
The saving in the percentage of failures is immense, as failure can scarcely
happen by this mode, and nearly 50 per cent. of the work done before was
unfit for subsequent use.
The mode of using this process for dental purposes is as follows:-The alloy
which I find most useful and cheapest in dentistry melts at a temperature of
400 degrees of the thermometer made for "Ashe's vulcanizer," and is com-
posed of two parts lead and one part tin. The cauldron containing this is placed
over a single jet of gas, and the alloy melts in about ten minutes; the case
with work perfectly dry is then laid into it, and a screw or weight, as before
described, laid on. The work is allowed to remain in the bath gradually
cooling to 300°, at which temperature the alloy is quite hard and requires
heating again to 400° to extricate the work (the second heating would become
unnecessary if a more fusible alloy were used which would melt at 300°, and
which might be obtained from bismuth at some additional expence). This
method occupies about an hour and a half, but varies with the rubber and
thickness of the work, the thicker the work the longer being the time occupied
in the process. I do not think the time could be well shortened for dental
purposes, but of course a much greater heat could be applied, if desired, by
changing the alloy. I find the average gain in unspoiled work for dentistry

page_text: to be about 75 per cent., while all the work is superior to that made by the
vulcanizers hitherto in use.
Having now described the nature and object of my said Invention for
"Improvements in Baking. or Hardening Vulcanite or Dental India-rubber
and other similar Compounds and Preparations, and in Apparatus employed
for such Purpose," together with the manner in which the same is to be or
may be performed or carried into practical effect, I would remark in con-
clusion that I claim as my Invention the use of a bath of molten metal or
alloy, in the manner and for the purposes above more particularly set forth.
In witness whereof, I, the said Frederick Ryding, have hereunto set my
hand and seal, this Seventh day of September, in the year of our Lord
One thousand eight hundred and sixty-seven.
FREDERICK RYDING. (L.S.)
Witness,
THOMAS HUGH KENNY.