AN IMPROVED METHOD OF MANUFACTURING ARTIFICIAL MARBLE
Year: 1839

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOSEPH
CLINTON ROBERTSON, late of Peterborough Court, Fleet Street, but now of
166, Fleet Street, in the City of London, Patent Agent, send greeting.
WHEREAS Her present most Excellent 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-seventh day of
September, in the third year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me, the said Joseph Clinton Robertson, my
exors, adors, and assigns, Her especial licence, full power, sole privilege
and authority, that I, the said Joseph Clinton Robertson, my exors, adñiors,
and assigns, and such others as I, the said Joseph Clinton Robertson, my exors,
adiiors, and assigns, should at any time agree with, and no others, from time
to time and at all times during the term of years therein expressed, should
and lawfully might make, use, exercise, and vend, within that part of IIer
said Majesty's United Kingdom of Great Britain and Ireland called England,
Her Dominion of Wales, Town of Berwick-upon-Tweed, and also in all Her
said Majesty's Colonies and Plantations abroad, an Invention, communicated
to me by a certain foreigner residing abroad, of "AN IMPROVED METHOD OF
MANUFACTURING ARTIFICIAL MARBLE;" in which said Letters Patent is contained:
a proviso, that I, the said Joseph Clinton Robertson, shall cause a particular-
description of the nature of the said Invention so communicated to me.
as aforesaid, and the manner in which the same is to be performed, to
be inrolled in Her said Majesty's High Court of Chancery within six calendar
months next and immediately after the date of the said in part recited Letters
Patent, as in and by the same, reference being thereunto bad, will more fully
and at large appear..

page_text: NOW KNOW YE, that, in pursuance of the said proviso, and in com-
pliance therewith, I, the said Joseph Clinton Robertson, do hereby declare
that the improved method of manufacturing artificial marble, communicated
to me by a foreigner residing abroad as aforesaid, consists in so preparing or
treating gypsum, or alabaster, or any other variety of native sulphate of lime
with a solution of any of the alkaline salts, but particularly with common salt,
sulphate of potash, alum, or saltpetre, and in afterwards polishing and coloring
the same, so as to give it more or less the hardness and appearance of
marble; and the manner in which the said Invention is to be performed or
carried into effect is as follows, that is to say:-
A block or piece of the native sulphate of lime is first sawn, hewn, chiselled,
or otherwise formed into the slab, pedestal, pillar, urn, or other article which
it is desired to have of the appearance of marble, taking care to select from
the blocks or pieces at hand the one most resembling the description of marble
sought to be imitated. The article so formed, and which I will suppose to be
of gypsum, is to be smoothed with fine files, glass paper, or other means, and
is then to be put into an oven or otherwise subjected to heat until the greater
part of the water of crystallization is driven off. Great nicety is required in
graduating the heat according to the solidity of the texture of the gypsum, so
that the water of crystallization may not be wholly evaporated. For the
purpose of being able to examine conveniently the article while undergoing the
process of desiccation, it is placed upon a grating, or sliding plate, or platform,
with a handle or other suitable means of withdrawing it from and returning it
to the oven. Great care should be taken in moving the article backwards and
.forwards, and in examining or handling it, for while it is in this hot state it is
very fragile and liable to fall in pieces. The article having been brought to
the desired state of dryness is withdrawn from the oven, and allowed to stand
for about a quarter of an hour, but not sufficiently long to imbibe damp
or moisture from the surrounding atmosphere. If it is desired to give the
article the appearance of natural white marble, it is immersed in a hot saturated
solution of common salt, sulphate of potash, alum, saltpetre, or any other
alkaline salt, and loft to soak in it till it ceases to absorb any more of the
solution; it is then withdrawn from the solution and exposed to the atino-
,sphere for two or three days, after which it is found to have obtained hardness
enough to be able to bear a high polish, which may be given to it in the same
way that natural marble or alabaster is usually polished. When it is desired
to give the article the appearance of any marble of a dark color or mixture of
colors, any of the dyes commonly used in dyeing cloths or silks are used, adding
the same to the saturated solution of salt before described previously to the

page_text: article being immersed therein. The quantity of dye stuff necessary to be
added to the saturated solution of salt to produce any particular shade of color
is readily ascertained by dipping a piece of white paper in the colored saline
solution, and then drying the same. The following tints or colors are stated to
me to be well and conveniently produced by the dyes or pigments herein-after
mentioned, that is to say, for deep grey, Campeachy wood, alum, and green
copperas for yellow, saffron and green copperas; for cardinal, orchilla root;
for rose colour, Brazil wood; for red and violet, Brazil wood and green
copperas.
And having now fully described the Invention so communicated to me by a
foreigner residing abroad as aforesaid, I declare that I claim the improved
method of manufacturing artificial marble before described and exemplified,
that is to say, the method of giving to slabs, pedestals, pillars, urns, and other
articles formed out of gypsum, or alabaster, or other variety of native sulphate
of lime the appearance and resemblance of real marble, by first desiccating the
same, and then immersing or steeping them in a solution of common salt,
sulphate of potash, alum, saltpetre, or other alkaline salt, and either with or
without an admixture of colors or dyes as aforesaid, and whether such
appearance or resemblance be produced by the exact mode of operation
herein-before described, or by any variation of the same, so long as the like
effect is produced by a like combination of materials and means.
In witness whereof, I, the said Joseph Clinton Robertson, have hereunto
set my hand and seal, this Twenty-seventh day of March, One
thousand eight hondaland Char