Improvements in the Production of Ornamental Stones Artificially Coloured.
Year: 1892

page_text: Date of Application, 28th Oct., 1892-Accepted, 3rd Dec., 1892
COMPLETE STUITIVATION.
Improvements in the Production of Ornamental Stones Artificially
Coloured.
I, PIERRE AIGNAU MOREAU, of Meang-sur-Loire (Loiret) in the Republic of
France, Marble Workman, do hereby declare the nature of this invention and in
what manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement :-
My invention relates to the coloration of natural or artificial stones of various
kinds, and is applicable to those, and those only, which are sufficiently porous to
absorb the requisite colouring solutions. According to my invention I cause the
colours to penetrate to a considerable depth into the stone, the limiting depth of
Thus with blocks which do not
penetration varying for different kinds of stone.
exceed in thickness double the depth to which the colour can penetrate, I can
secure the penetration of the colours throughout the block so that the block may
after coloration be cut up into slabs, each slab being thus coloured throughout.
The principal object of my invention is to produce stones of variegated hues,
diversely veined and coloured, preferably so as to resemble as far as may be natural
ornamental stones.
According to my invention, the rough block of chalk or other porous stone or the
sculptured or moulded object of natural or artificial porous stone is first dried and
then coated externally in certain parts with a protective varnish which prevents the
coated parts of the stone from absorbing the colouring solutions to the same
extent as the other parts. This coating may, for instance, imitate the venation of
natural marble.
The coated stone is then immersed in a series of colouring baths. The uncoated
parts of the stone absorb the colouring solutions whilst the protective coating on
the other parts of the stone wholly or partially prevents such absorption. The
result is that the colour penetrates the stone irregularly, the irregularities being
determined not merely by the outlines of the protective coating but also by the
natural irregularities of the stone, ornamental effects of coloration being thus
produced, not merely on the exterior of the stone, but in the substance of the stone
itself.
Stones thus coloured, as above described, may be used in their soft state for some
purposes, but I prefer to harden them by drying and immersing in a solution of
sulphate of zinc, as described in the Specification of my application for Letters
Patent No. 50 of the year 1892, or by any other suitable process of hardening.
After hardening the stones may be polished. Or the colour of the stones may be
brought out by rubbing them with oil or in other known ways.
Such being the general nature of my improved process, I will proceed to
describe its practical application in greater detail, and for this purpose will
describe it as applied to a slab of chalk of about one and a quarter inches in
thickness.
The slab should in the first instance be dried, this I have done in some cases by
allowing the slab to stand under cover with free access of air and in other cases by
means of currents of warm dry air produced by artificial means.
The slab being sufficiently dried, the surface has first of all to be covered with
the desired pattern of protective coating. This may be applied with a brush by
hand, or by means of transfer papers, or it may be dabbed on with a sponge or
otherwise impressed upon the surfaces and edges of the slab.
In order to produce a protective coating in the form of veins intended to
represent those of natural marble I prefer to effect the coating in a manner similar

page_text: to that which has been heretofore employed for superficial coloration. I take
varnish preferably made of a mixture of turpentine, gum thus, and sesquioxide of
iron in the proportions of about 3 lbs. of turpentine, 1 lb. of gum thus and about
3 ounces of sesquioxide of iron or rouge de Prusse. I drop a portion of this
varnish with a brush or rod in streaks and patches on the surface of a water bath.
The varnish spreads on the water and by means of the brush or rod the film of
varnish may be divided and distributed so as to imitate the natural veining of
marble. The surface of the slab is then laid upon the surface of the water and the
varnish adheres to the slab. In this manner the surfaces of the slab may be readily
covered with the requisite protective coating in a form suitable for producing an
imitation of the veins of marble.
The slab is then ready for treatment in the colour baths. If it is treated in the
colour baths before the protective coating is completely dry, the colour will to some
extent penetrate the coating. Thus by allowing the coating to dry more or less,
the results produced may be varied.
The process of coloration I will describe with reference to three baths composed
of solutions of

page_text: The protective coating may be removed by scraping or pumice stoning, and the
slab may be afterwards dried and, if desired, hardened as described in my
Specification No. 50 of the year 1892.
!
If a slab treated as above described be cut through, it will be found that the colours
have followed one another up in successive irregular layers, or perhaps they may be
better described as successive wave surfaces of colour. These successive surfaces
appear to be travelling through the stone during the successive immersions. To
some extent they catch one another up and interpenetrate in the interior of the
stone and produce resultant colours. Thus the sulphate of iron alone produces a
yellow tint, the sulphate of copper alone produces a green tint. But the blendings
of the two produce various shades of brown of an ornamental kind. The sulphate
of zinc appears to produce its effects chiefly by modifying and separating the
successive colour surfaces as they penetrate the stone.
It will be found that the layers of colour making their way through the uncovered
portions of the surface also penetrate through the substance of the stone under
the layers of protective coating and the edges of such layers come to the surface
in places beneath the protective coating and so diversify the result produced.
It will be seen that the process of coloration thus described admits of almost
indefinite variation by the use of different colours in different orders. Vegetable,
aniline and other dyes may be used and the interaction of the successive penetrating
layers will be sometimes chemical and sometimes mechanical. The chief advantages
of the use of successive immersions is that there is produced a succession of layers
or waves of colour travelling through the stone, blending and interpenetrating,
and modified by the natural inequalities of the stone, in such a way that the total
result is to produce. variegated, blended or veined colours of an ornamental
character, throughout the substance of the stone. In some cases I may use only
one colour bath, where only one tint of varying strengths is required, and the
required irregularities will then be produced solely by the varying thickness and
dryness of the superficial coating and the varying texture of the stone. But the
best results are produced by successive immersions as above described.
In treating Portland stone or Bath stone, or other harder stones by means of
the above process, the times of immersion will have to be considerably increased,
and in every case, the thicker the stone, the longer the periods required for
complete penetration of the colours into the interior. Moreover with harder stones
it will be found that a longer subsequent treatment with the hot bath is desirable,
and that the temperature of the bath should reach the higher limit.
The requisite times for penetration may easily be ascertained by immersing
trial blocks for one, two, three minutes or longer periods, and afterwards cutting
them across and noting the different depths of penetration. In the same way the
effect of the blending of various colours by successive immersions may also be
determined experimentally for different colours and different stones. It is
impossible to describe in words or even to shew by drawings the actual results
produced, which indeed vary to some extent in every case, but the immersion in
the baths A, B and C of slabs of chalk of the thickness and for the periods noted
above and the subsequent making of sections of such slabs will sufficiently
illustrate the principles and practice and results of the process to give a practical
guide to the workman.
The limits of penetration for useful purposes with any particular kind of stone
may in like manner be ascertained by trial blocks. I have in some cases
obtained useful results to a depth of 6 or 8 inches, so that blocks of double
that thickness may be coloured throughout the interior by my process with some
kinds of stone.
Where it is not intended to cut the blocks or portions treated into slabs, it is
obviously unnecessary that the colour should penetrate throughout the interior.
But in such cases the penetration of the colour enables the surface to be worked
to some depth without destroying the colour, as would be the case with merely
superficial coloration. Indeed, in some cases, the removal of the surface is an

page_text: .
advantage, as the colours in the subjacent layers often give better markings than
on the surface.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what [
claim is :-
1. The improved process of colouring natural or
substantially as hereinbefore described.
artificial porous stone,
2. The method of producing colour effects of the kind hereinbefore referred
to in porous stones by a series of immersions in colour baths, whereby irregular
layers or surfaces of colour are produced in the interior of the stone, substantially
as described.
3. The regulation of the colour effects in the penetration of the colour into
porous stones, by the use of a pattern of varnish or other protective coating suit-
able to prevent to a greater or less extent the penetration of the colour in the
requisite portions, substantially as described.
4. The method of producing ornamental slabs of artificially coloured stone, by
colouring the stone in blocks substantially in the manner hereinbefore described
and afterwards cutting the blocks into slabs.
5. As a new product, a natural or artificial stone coloured not merely on the
surface but also in the interior by means of the hereinbefore described process.
Dated this 28th day of October 1892.
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant..