Improvements connected with Stones for Lithographic Purposes.
Year: 1889

page_text: Date of Application, 14th Mar., 1889
Complete Specification Left, 14th Dec., 1889-Accepted, 18th Jan., 1890
PROVISIONAL SPECIFICATION.
Improvements connected with Stones for Lithographic Purposes.
I, THOMAS RUDDIMAN JOHNSTON of 26 Charterhouse Square, in the County of
Middlesex, Map Publisher, do hereby declare the nature of this invention to be as
follows:
Heretofore when lithographic stones have been worn too thin for ordinary use,
they have been cemented by Plaster of Paris, or other cement requiring to be mixed
with water, to slabs of slate or other stone.
Of late years the general use of great numbers of the larger sizes of steam printing
machines and other causes, have led to a great scarcity in the better quality of suitable
lithographic stones, and as the price of these is considerably higher in proportion than
that of smaller sizes, it has been suggested that the stones might be cut into
comparatively thin slabs and backed in some way with a cheaper material.
In the Specification of Letters Patent granted to Peter Stuart, dated November 15,
1882, No. 5441, it was proposed to strengthen lithographic stones with a certain
backing, but in practice this backing caused the lithographic slabs to become unlevel,
and they have broken when printed from, or without having been printed from, they
have been found to be cracked from some peculiar action of the cement used. In
other cases the stones and backing came apart in use.
Now according to my invention, I avoid the use of cements of the character herein-
before referred to, and I employ in lieu thereof, Asphalt, bitumen, pitch, shellac,
sulphur, or other like matters or cements, or combinations of the same, which will
readily melt by heat at a comparatively low temperature, without the addition of
water. I employ these materials, mixed or unmixed with chips of stone, ground
stone, sand, gravel, or other suitable solid material, as a backing to the lithographic
stone, or as a cement for securing the lithographic stone to a natural or artificial stone
backing.
One method in which I carry my invention into effect is somewhat as follows:-
I take a slab of lithographic stone and heat it in any convenient manner to about
the melting point of the cement used, say as an example Seyssel Asphalt. The
Asphalt having been melted with a small quantity of pitch or mineral tar, and allowed
to boil for 4 or 5 hours to remove the volatile oils, I then paint the back of the slab
of stone with this melted Asphalt.
To the edges of the face of the stone, I then paste bands of papor, and having laid
the slab face downwards, I fold these upwards, joining them together, so that they,
with the back of the stone, will form a shallow trough, and support the paper at
each side with a strip of wood; or I form a trough on the back of the stone in any
other convenient manner. I then pour a small quantity of the melted Asphalt into
the trough, dropping at once into it, the chips of stone, ground stone, sand, gravel,
or other material, which has been previously heated; more Asphalt run in, and more
stone or other like material added, until the desired thickness is attained. The stone
or other like material may, if desired, be previously mixed with the Asphalt.
To join a slab of lithographic stone to a slab of natural or artificial stone, I heat
both of these until they are warmer than the melting point of the Asphalt or other
cementing material used. I then place at suitable distances, small pieces of wood or
other material on the backing stone, of a thickness to correspond with the intended
thickness of the layer of Asphalt or other cementing_material.
The slab of lithographic stone and the backing, I now clamp firmly together, and
having pasted paper around, or otherwise closed, three sides of the space between the

page_text: stones, to prevent the escape of the Asphalt or other cementing material, I turn the
stones up on edge and pour the melted Asphalt or other cementing material between
them.
Dated this 14th day of March 1889
THOMAS RUDDIMAN JOHNSTON.
By Harris & Mills,
23 Southampton Buildings, Agents.
COMPLETE SPECIFICATION.
Improvements connected with Stones for Lithographic Purposes.
I, THOMAS RUDDIMAN JOHNSTON, of 26 Charterhouse Square, in the County of
Middlesex, Map publisher, do hereby declare the nature of this invention and
in what manner the same is to be performed to be particularly described and
ascertained in 'and by the following statement:—
Heretofore when lithographic stones have been worn too thin for ordinary use, they
have been cemented to slabs of slate or other stone by means of Plaster of Paris or
other cement requiring to be mixed with water.
Of late years, the general use of great numbers of the larger sizes of steam printing
machines, and other causes, have led to a great scarcity in the better quality of
suitable lithographic stones, and as the price of these is considerably higher in
proportion; than that of smaller sizes, it has been suggested that the stones might be
cut into comparatively thin slabs and backed in some way with a cheaper material.
In the specification of Letters Patent granted to Peter Stuart dated November 15.
1882. No. 5441, it was proposed to strengthen lithographic stones with a backing of
artificial stone composed of ground granite, sand or like material, and Portland,
Roman, or other like cement, but in practice this backing caused the lithographic slabs
to become unlevel, and they have broken when printed from, or, without having been
printed from, they have been found to be cracked from some peculiar action of the
cement used. In other cases the stones and backing came apart in use.
Now according to my invention, 1 avoid the use of cements of the character
hereinbefore referred to, and I employ in lieu thereof Asphalt or bitumen ór
combinations of the same with mineral pitch or mineral tar, which will readily melt
by beat at a comparatively low temperature without the addition of water and which
will form a slightly olastic backing or cementing material.
I employ these materials, mixed or unmixed with chips of stone, ground stone, sand,
gravel, or other suitable solid material, as a backing to the lithographic stone, or as a
cement for securing the lithographic stone to a natural or artificial stone backing.
I will describe my invention with reference to the accompanying drawings, in
which Figure. 1. is a plan and Figure. 2. a cross section representing the means
I adopt for backing a slab of lithographic stone with artificial stone and Figure. 3.
is an end view, and Figure 4 is a plan representing the means I adopt for
cementing a slab of lithographic stone to a slab of other natural or artificial
stone.
One method in which I carry my invention into effect is somewhat as follows :-
I take a slab of lithographic stone and heat it in any convenient manner to
about the melting point of the cement used, say as an example, Soyssel Asphalt.
The Asphalt having been melted with a small quantity of mineral pitch or mineral
tar, say about 5 per cent. (more or less) to obtain the required fluidity or consistence,
and allowed to boil for 4 or 5 hours to remove the volatile oils, I then paint the
back of the slab of stone a with this melted asphalt and pitch or tar.
To the edges of the face of the stone a I then cement bands b of paper, and
having laid the slab face downwards, I fold these upwards, joining them together,
so that they, with the back of the stone a, will form a shallow trough, and 1
support the paper'b at each side with a strip of wood c, which strips. may be long

page_text: enough to suit various sizes of stones, in which case they are arranged as represented
at Figure 1. and they are preferably fixed together by staple formed connecting
irons d; or I form a trough on the back of the stone in any other convenient
manner. I then pour a small quantity of the melted Asphalt and pitch or tar
into the trough, dropping at once into it, the chips of stone, ground stone, sand,
gravel, or other material, which has been previously heated; more melted asphalt
and pitch or tar is run in and more stone or other liko material added, this operation
is repeated until the desired thickness is attained. The surface of the compound
forming the backing is then pressed and flattened, after which it is left to cool, by
which means a solid durable backing is firmly attached to the slab of lithographic
stone a, which backing is not liable to twist or warp in setting, nor to become
accidentally detached from the slab of lithographic stone a. The stone or other like
material to form the backing may, if desired, be previously mixed with the melted
asphalt and pitch or tar.
To join a slab of lithographic stone a to a slab of other natural or artificial
stone e, I heat both of these until they are warmer than the melting point of the
Asphalt or other like cementing material used. I then place at suitable distances,
small pieces of wood or other material f on the backing stone, of a thickness to
correspond with the intended thickness of the layer of Asphalt or other like cementing
material used to connect the slab of lithographic stone a and the backing stone e*
together.
The slab of lithographic stone a and the backing e* 1 now clamp firmly together by
means of screw clamps g or by other suitable means, and having cemented paper b
around, or otherwise closed, three sides of the space between the two stones, to
prevent the escape of the Asphalt or other like cementing material, I turn the
stones up on edge and pour the melted asphalt or other like cementing material
between them.
I would here remark that the other cementing materials named in my provisional
specification do not possess such an amount of utility as to render it advisable to
make a claim thereto.
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 I
claim is :-
1. A backing for lithographic stone, consisting of either natural or artificial stone
connected to the slab of lithographic stone by Asphalt or bitumen or combinations
of the same with mineral pitch or mineral tar, substantially as horein described.
2. A backing for lithographic stone consisting of asphalt or bitumon or compounds
of the same with mineral pitch or mineral tar mixed with chips of stone, ground
stone, sand, gravel or other material, and connected to the lithographic stono by
such cements or materials, substantially as herein described.
3. A cement for combining materials to form a backing to slabs of lithographic
stone and to connect the same or other backing thereto composed of Asphalt or
bitumen or combinations of the same with mineral pitch or mineral tar substantially
as herein described and for the purpose stated.
4. A stone for lithographic purposes consisting of a slab of lithographic stone and
a backing cemented thereto by the materials named in the preceding claims
hatan 11.
1
THOMAS RUDDIMAN JOHNSTON.
By Harris & Mills,
23, Southampton Buildings, London, Agents.