IMPROVEMENTS IN THE MANUFACTURE OF ARTIFICIAL STONE AND MARBLE AND IN COLOURING THE SAME
Year: 1881

page_text: ETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, for an Invention of "IMPROVEMENTS IN
THE MANUFACTURE OF ARTIFICIAL STONE AND MARBLE AND IN COLOURING
THE SAME." A communication from abroad by La Société Anonyme
de Certaldo, represented by William Rey, Director of the Company, and
Charles Victor Crosnier de Varigny, Chairman of the Company, both of Paris,
in the Republic of France.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at the
Office of the Commissioners of Patents on the 28th July 1881.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN THE MANUFACTURE OF ARTIFICIAL STONE AND
MARBLE AND IN COLORING THE SAME." A communication from abroad by La
Société Anonyme de Certaldo, represented by William Rey, Director of the
Company, and Charles Victor Crosnier de Varigny, Chairman of the Company, both
of Paris, in the Republic of France.
This Invention relates to the manufacture of artificial stone and marble, and
it consists in an improved process hereinafter described for indurating and
coloring substances, having sulphate of lime as their base, such, for example, as
gypsum or plaster of Paris, alabastrite, and the like, when in a crude or
inanufactured condition.
In carrying out the said Invention the materials to be indurated are first
dehydrated in a stove or furnace or by other suitable means, after which they are
placed in a vessel or apparatus of suitable construction and exposed to the action
of the following chemical products employed either singly or in combination,
videlicet, sulphate of iron, oxalic acid, carbonate of potash, sulphate of soda, salts
of magnesia, sulphate of alumina, and the like.

page_text: By these means the desired degree of hardness is imparted to the substance
under treatment. The said substances may be submitted to the indurating action
of the chemicals hereinbefore described, either in a crude or unwrought condition,
or after they have been wrought or formed into the shape of the finished article.
An imitation of white marble is obtained by treating the materials in the
manner hereinbefore described, but in order to obtain imitations of colored
marbles the plaster of Paris or other material having sulphate of lime as a base
is caused to assume any desired shade of color by the employment of suitable
coloring matter applied by preference in the indurating process hereinbefore
described.
The desired color is produced by the employment of materials which are
decomposed by contact with the substances to be indurated or which remain
unchanged in presence of the latter.
The coloring action is caused by chemical reactions, and a partial deposition
forming veins in imitation of the veins in natural colored marble.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Henry Johnson in the Great Seal Patent Office on the
28th January 1882.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN THE MANUFACTURE OF ARTIFICIAL STONE AND
MARBLE AND IN COLOURING THE SAME." A communication from abroad by La
Société Anonyme de Certaldo, represented by William Rey, Director of the
Company, and Charles Victor Crosier de Varigny, Chairman of the Company,
both of Paris, in the Republic of France.
This Invention relates to the manufacture of artificial stone and marble, and
to coloring the same, and consists in an improved process hereinafter described for.
indurating or hardening and coloring articles composed of materials having sulphate
of lime as their base, such for example as blocks of gypsum, or plaster of Paris,
alabastrite, and the like.
Artificial stone or marble obtained by this improved process is termed by the
inventors "certaldite," and is prepared by first dehydrating or removing the
water from articles composed of plaster of Paris, gypsum, alabastrite, for example,
and afterwards submitting them to the action of certain chemical agents, as
hereinafter described, with or without the addition of means or agents for coloring
the same.
In order to dehydrate the articles or materials before mentioned, whether they
be in a rough or uncut condition or in a manufactured form, the said articles or
materials are baked in a stove or other suitable dehydrating or drying apparatus
without being brought into direct contact with the fire. The duration of the.
dehydrating process and the degree of temperature employed will vary according
to the nature or grain and the dimensions of the article or material being treated.
In the case, for example, of the gypsum obtained from Certaldo, in Italy, when in
the form of blocks or manufactured articles, an exposure to a temperature of from
about one hundred and ten to one hundred and twenty degrees centrigrade for a
period of about twelve hours will usually be found sufficient. Blocks or articles
made of plaster of Paris also require baking for about twelve hours. But
the temperature in this case must be from about one hundred and fifty to one
hundred and seventy degrees centigrade. When treating blocks or articles
exceeding about one or one and a half inches in thickness the operation will
require more time and is known to be completed when a fracture of the block
presents a uniform white color throughout.
When the process of dehydration is complete the block or article is left to cool
for one or two hours, and is then immersed in a bath in order to be hardened or
indurated. The substances employed in the preparation of this bath are the
following, videlicet: salts of magnesia, carbonate of potash or soda, sulphate of
potash or soda, sulphates of iron and copper, alum, nitric, sulphuric, acetic, or
oxalic acids, ammonia, bichromate of potash, potash cyanide of potassium, acetates,
oxalates, sulphates, nitrates, carbonates, or the equivalents of these which will not
decompose gypsum or plaster of Paris, and are capable of imparting hardness
thereto, such substances combining with the gypsum or plaster of Paris, and either
by filling the spaces which, before dehydrating, were occupied by the molecules of
water or by becoming chemically blended with the elements of the said gypsum or
plaster of Paris.
The hereinbefore mentioned substances employed in the preparation of the

page_text: herein before mentioned bath are selected according to the nature of the reactions
which take place when the said substances are brought into contact with gypsum
or plaster of Paris, their effect upon the stability and fixing of the colors when
coloring matters are employed being also taken into consideration.
The
By the treatment as described the desired degree of hardness is imparted to the
materials under treatment to convert them into artificial stone or marble.
said materials may be submitted to the indurating action of the hereinbefore
described bath either in a rough or unwrought condition, or after they have been
wrought or formed into the shape of the finished article.
And in order that the said Invention may be fully understood, I will describe
the means by which white certaldite may be manufactured according to this
Invention.
Slabs or blocks of gypsum or plaster of Paris cut or sawn to a thickness of about
one inch are heated in a stove.for a period of from twelve to eighteen hours at a
temperature ranging from about one hundred to one hundred and fifty degrees
centigrade.
In treating thicker blocks or slabs a somewhat higher temperature will be
*required.
This operation of dehydration or driving off the water is of great importance,
and care must be taken not to allow the temperature to rise to an excessive extent,
as this would render the materials liable to crack, and become injured by the
subsequent treatment in the bath. The completion of the dehydrating process
throughout the whole of the materials under treatment may be ascertained by
examining the grain of the fracture by means of a suitable sample or test
piece.
•
After removal from this stove the slabs, blocks, or articles are allowed to cool for
a few hours, and they are then immersed in a bath composed of about six and a
half pounds of carbonate of potash, for example, with about twenty two gallons of
water. The said slabs, blocks, or articles are allowed to remain in this bath for
about two or three seconds, after which they are taken out and allowed to dry
for a few seconds, being then again plunged into the bath for about six or eight
seconds and again allowed to dry. This process of alternate iminersing and drying
is carried on for about half an hour. At the expiration of about half or three
quarters of an hour the blocks will have become extremely hard, and are then
--immersed-continuously-for-about-twelve-hours.in.the-same-bath..
White "certaldite" may also be produced by means of sulphate of iron. In this
case the bath is composed of about two pounds of sulphate of iron to about twenty
two gallons of water.
Colour is imparted to the product either by the reactions of two or more of the
substances herein before enumerated or by the addition of suitable organic or
mineral colouring matter, which is mingled with the indurating materials in
the bath.
After being submitted to the action of the bath the blocks are dried by being
exposed to the sun, or to a temperature of from about thirty to forty degrees
centigrade, for from about one to two hours, after which they are painted over with
oil two or three times.
The artificial marble or stone thus produced is now ready for polishing.
This operation is or may be performed by employing cast iron plates with sand
and water in the first place, and afterwards water alone, or by other suitable
means.
In order to produce a rose coloured "certaldite" the bath may be composed of
the following ingredients, videlicet:—
Water, about
22 gallons.

page_text: An artificial black marble may be produced by employing a bath consisting of-
Water
Oxalic acid
Extract of logwood
"
"
gallnuts
23
در
sumach or fustic
about 22 gallons.
3
"
"
ounces.
13 lb.
11
Sulphate of iron
"
2
"3
">
"
4
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and original,
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is,-
Treating slabs, blocks, or articles composed of gypsum, plaster of Paris, or having
sulphate of lime as their base by first dehydrating or drying them, and afterwards
indurating them by subjecting them to the action of a bath composed substantially
as herein before described, whether for producing a white or a coloured "certaldite,"
or artificial stone or marble.
In witness whereof, I, the said John Henry Johnson, have to this my
Specification set my hand and seal, this Twenty-seventh day of January,
One thousand eight hundred and eighty two.
J. HENRY JOHNSON. (LS.)