AN IMPROVEMENT IN THE MANUFACTURE OF RUBBERS FOR PAINTERS AND OTHERS
Year: 1855

page_text: LETTERS PATENT to Charles Henry Roberts, of 3, Cornwall Road, Stam-
ford Street, Lambeth, in the County of Surrey, for the Invention of "AN
IMPROVEMENT IN THE MANUFACTURE OF RUBBERS FOR PAINTERS AND OTHERS."
Sealed the 24th April 1855, and dated the 26th February 1855.
PROVISIONAL SPECIFICATION left by the said Charles Henry Roberts
at the Office of the Commissioners of Patents, with his Petition, on the
26th February 1855.
I, CHARLES HENRY ROBERTS, of 3, Cornwall Road, Stamford Street, Lam-
beth, in the County of Surrey, do hereby declare the nature of the Invention
for "AN IMPROVEMENT IN THE MANUFACTURE OF RUBBERS FOR PAINTERS AND
OTHERS" to be as follows:-
This Invention has for its object the use of ground pumice stone in the
manufacture of artificial rubbers, in place of employing pumice stone in the
natural state. For this purpose, pumice stone is to be crushed or reduced to
more or less fine granular states, which being separated into different degrees
of fineness are each to be cemented and formed into moulded blocks or shapes;
and although other cementing materials may be employed, it is preferred to
use soluble silicates.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Charles Henry Roberts in the Great Seal Patent Office
on the 18th August 1855.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
HENRY ROBERTS, of 3, Cornwall Road, Stamford Street, Lambeth, in the
County of Surrey, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-sixth day of February, in the year of our Lord
One thousand eight hundred and fifty-five, in the eighteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Charles Henry Roberts, Her special licence that I, the said Charles Henry
Roberts, my executors, administrators, and assigns, or such others as I, the said
Charles Henry Roberts, 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 "AN IM-
PROVEMENT IN THE MANUFACTURE OF RUBBERS FOR PAINTERS AND OTHERS," upon the
condition (amongst others) that I, the said Charles Henry Roberts, by an instru-
ment in writing under my hand and seal, should particularly describe and ascer-
tain 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 Charles Henry Roberts, do hereby
declare the nature of the said Invention, and in what manner the same is
to be performed, to be particularly described and ascertained in and by the
following statement thereof (that is to say) :-
This Invention has for its object the use of ground pumice stone in the
manufacture of artificial rubbers in place of employing pumice stone in the
natural state. For this purpose pumice stone is to be crushed or reduced to
more or less fine granular states, which being separated into different degrees
of fineness, are each to be cemented and formed into moulded blocks or shapes;
and although other cementing materials may be employed, it is preferred to
use soluble silicate.
Having thus stated the nature of my said Invention, I will proceed to
describe more fully the manner of performing the same.
The pumice stone is first to be reduced into a granular state, and the same

page_text: is then to be separated into different degrees of fineness. And I have found
that three degrees of fineness are sufficient for practical purposes; and I cause
the ground or crushed pumice stone to be passed through three sizes of sieves;
the first with eighty holes to the inch, the second sixty holes to the inch,
and the third, fifty holes to the inch. This, however, may be varied, and finer
or coarser grit of pumice stone obtained and made up into moulded blocks or
forms as rubbers. These separated qualities of grit of pumice stone are then
to be combined by cement, for which purpose I employ soluble silicates, as is
well understood in the manufacture of artificial stone, and to the use of which
separately as a means of cementing matters together I make no claim; and I
employ as little of such soluble silicate as may be to mix up with the grit of
pumice stone; and I press the mixtures in moulds of the forms of the intended
rubbers, preferring metal moulds for this purpose; and I allow the moulded
rubbers to set and dry, and then subject them to a dull red heat in a stove or
kiln, in like manner to what artificial stone (when using soluble silicates as the
cementing material) have been before heated. The rubbers, when cold, are
then in a condition to be used, and thus is a comparatively cheap pumice stone
made up into uniform qualities of rubbers of different degrees of fineness, by
which the use of pumice stone rubbers thereof will be greatly improved, and
they will be found superior by reason of their uniformity of grit or "cut" to
rubbers of pumice in their natural or unmanufactured state.
The proportions I have employed are 1 cwt. of the grit of pumice stone to
thirty pounds of solution of silicate of soda of specific gravity 1-360, well
mixed and pressed into the moulds.
In witness whereof, I, the said Charles Henry Roberts, have hereunto
set my hand and seal, this First day of August, in the year of our
Lord One thousand eight hundred and fifty-five.
Witness,
B. GOBBY,
CHARLES H. ROBERTS. (L.S.)
4, Old Square, Lincoln's Inn.