IMPROVEMENTS IN THE APPLICATION OF SILICATE OF POTASH TO, HARDENING AND PRESERVING STONES AND CALCAREOUS MATERIALS
Year: 1855

page_text: LETTERS PATENT to William Armand Gilbee, of the English and Foreign
Patent Office, 39, Rue de l'Echiquier, Paris, France, and of 4, South
Street, Finsbury, London, for the Invention of "IMPROVEMENTS IN THE
APPLICATION OF SILICATE OF POTASH TO, HARDENING AND PRESERVING STONES
AND CALCAREOUS MATERIALS." -A communication.
31
PROVISIONAL SPECIFICATION left by the said William Armand Gilbee
at the Office of the Commissioners of Patents, with his Petition, on the
19th October 1855.
I WILLIAM ARMAND GILBEE, of the English and Foreign Patent Office,
39, Rue de l'Echiquier, Paris, France, and of 4, South Street, Finsbury,.
London, do hereby declare the nature of the Invention of "IMPROVEMENTS IN
THE APPLICATION OF SILICATE OF POTASH TO HARDENING AND PRESERVING STONES
AND CALCAREOUS MATERIALS," to be as follows, that is to say :-****;
The Invention consists in the following improvements, in the application
of silicate of potash to the hardening & preservation of stones and other
calcareous materials:
1st, the degree of strength of silicate of potash to be employed is from
3° to 15° Beaumé, according to the nature, porosity, or decay of the stone.or
calcareous materials..

page_text: 2nd, the employment, according to the position in which the stone or
calcareous materials are exposed, or to their state of dampness, of ordinary
ventilators, or, by preference, of Combe's ventilators, to inject air, which may
be heated to a temperature of 60° to 160° centigrade, in order to bring them
to the required state of dessication and porosity, to enable them to imbibe
the necessary quantity of silicate of potash. The air is injected by means of
tubes.
3rd, the introduction of the required quantity of silicate of potash, which
is variable from 2 to 15 lbs. per superficial yard, according to the nature,
porosity, or decay of the stone or calcareous materials, by means of pumps,
giving a fine injection in the form of rain, which injection is to be continued
during 3 to 5 days, according to circumstances.
4th, the effecting the dessication of the silex introduced into the stones or
calcareous materials by means of ventilators, preferably of Combe's ventilators,
when the atmospheric influences are not favorable.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William Armand Gilbee in the Great Seal Patent Office on
the 12th April 1856.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
ARMAND GILBEE, of the English and Foreign Patent Office, 39, Rue de
l'Echiquier, Paris, France, and of 4, South Street, Finsbury, London, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Nineteenth day of October, in the year of our Lord
One thousand eight hundred and fifty-five, in the nineteenth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William Armand Gilbee, Her special license, that I, the said William
Armand Gilbee, my executors, administrators, and assigns, or such others as
I, the said William Armand Gilbee, 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 "Im-
PROVEMENTS IN THE APPLICATION OF SILICATE OF POTASH TO HARDENING AND
PRESERVING STONES AND CALCAREOUS MATERIALS," a communication from a

page_text: foreigner residing abroad, upon the condition (amongst others) that I, the
said William Armand Gilbee, by an instrument in writing under my hand
and seal, 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 William Armand Gilbee, 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 consists, firstly, in the process of impregnating stone and
other calcareous materials with a solution of silicate of potash.
Secondly, in determining the different degrees of strength to be given to the
solution of silicate of potash, which varies according to the nature and state of
the stone and the conditions of the atmosphere.
Thirdly, in the means of drying the stone either before or after the satu-
ration, to ensure a favorable result. When treating calcareous materials by
the above operations, a certain quantity of carbonate of lime is converted
into silicate of lime. The silicatisation also of siliceous materials, such as
sandstone, is effected by the introduction of a solution of pure silicate of
potash, which in setting causes the disintegrated particles of sand to adhere,
thus hardening the stone to a considerable extent. Before proceeding to the
silicatisation of the materials, it is necessary, if they are new, to dust them,
and if old and decayed, to clean them, carefully avoiding the use of acid. If
the monuments or materials to be treated have been previously coated with
a waterproof composition, it is requisite after the removal of this coating to
wash them with an alkaline solution of from two degrees to seven degrees
Baumé, according to circumstances, and afterwards to wash them with pure
water.
The solution of silicate of potash is applied to the stone in the form of fine
rain, by means of suitable pumps furnished with spreaders. In treating hard
stones, this process is continued for three or four days successively, but for soft
stones four or five days are necessary. The process is discontinued when small
crystals of quartz appear on the surface of the stone, this state being a proof
of sufficient impregnation. The quantity of the solution of silicate of potash
may vary from two pounds to fifteen pounds per superficial yard, according to
the nature and decay of the stone or calcareous material: During the process
attention must be paid to the temperature, and the degree of dryness or
humidity of the atmosphere, and to the state of desiccation of the stone, to
.

page_text: compensate for the evaporation of the silicate solution, by diluting it more or
less, according to the proportion; herein-after stated.
.
On account of the variety in the quality of building stones, I'divide them
into three classes, so as to indicate as clearly as possible the degree of con-
centration of the solution requisite in each case. First, hard stones (sandstone,
rock lias); second, soft stones (large grains and open pores); third, soft stone
with close grains, such as calcáreous stone, obtained from the bed of the
Loire.
t The stones of the first class åre treated with a silicate solution of the
strength of seven degrees to nine degrees Baumé: A solution of five to seven
degrees Baumé. is applied to those of the second class; gradually diluting
it, so as to finish with a solution equal to ten degrees to twelve degrees
Baumé..
c
:
The materials of the third class are treated with a solution from six degrees
to seven degrees Baumé, which is gradually lessened, so that in completing
the operation the strength of the solution is not more than three to four
degrees Baumé. In all cases I avoid the 'complete stoppage of the pores of
the stone.
...
.. The treatment. described for materials of the first class is also applicable to
new. or decayed statuary marble; that for stones of, the second class for all
kinds of: sandstone: When they are much decayed I employ 'a' more con-
centrated solution of the silicate of potash.
""
In cases where, by reason of the condition of the atmosphere or the position
the stone occupies, it fails to attain a sufficient degree of silicatisation, I dry it
by means of ventilators (that of Combe's being preferred), employing heated
air, according to circumstances: In order to dry the stones by heated. air
previous to silicatisation, I commence at a temperature of one hundred and
four degrees Fahrenheit, which I raise gradually during the necessary time to
three hundred and eighteen degrees Fahrenheit, and even higher, according
to. circumstances, reducing it gradually to the original degree of heat. I
operate in the same manner after silicatisation.
I also employ heated air for joining stones, for which purpose good hydraulic
cement is used, mixed with silicate of potash-from eight to 'ten 'degrees Baumé.
¡Detached portions of stone are' replaced by a' paste or cement formed of the
same kind of stone, broken and sifted and mixed with a silicate: solution" of
twenty-five to thirty degrees Baumé, afterwards properly compressed' so as to
assume.. the exact color; grain, and density of the natural stone. The same
process of joining and restoration can be applied to sandstone and statuary
..marble..

page_text: When joints made by the ordinary process of lime cement give way, they
may be strengthened by impregnating them with successive coatings of silicate
of potash of ten to twelve degrees Baumé. This impregnation is effected by
means of pressure continued during a day or more. The result may be
improved by applying after the last application of silicate of potash, acetic
or pyroligneous acid of 2° B., succeeded immediately by showers of clean
water.
Having now described the nature of the said Invention, and the manner
in which the same is to be performed, I would have it understood that I do
not confine myself to the precise details herein laid down; but what I claim
is, the processes for applying silicate of potash to the preservation and restora-
tion of monuments, statues, and sculptures constructed of calcareous and other
stones; and also to the treatment of calcareous and other stones separately, as
herein-before described.
In witness whereof, I, the said William Armand Gilbee, have hereunto
set my hand and seal, this Eleventh day of April, One thousand eight
hundred and fifty-six.