Improvements in or relating to the Treatment of Lithographic Stones and the like.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in or relating to the Treatment of Lithographic Stones
and the like.
We, JOSEPH SPEDDING CURWEN, of 8 and 9, Warwick Lane, E.C., and Plaistow,
in the County of Essex, Music Printer and Publisher, and ALFRED HERBERT,
c/o J. Curwen & Sons Limited, North Street, Plaistow, in the County of Essex,
Lithographer, do hereby declare the nature of this invention to be as follows:-
By the old method of treatment the lettering or design which has been printed
from a lithograph stone has to be removed by the labourious and wasteful process
of grinding the face of the stone with pumice powder or sand until the greasy
ink of the transfer which has penetrated the stone has been ground completely
away.
By our method every trace of the former lettering or design is effectually
obliterated by washing over the face of the stone with a chemical compound and
it is in the composition of this compound that our invention consists.
We make an admixture of a compound of an alkaline earth (such as calcium,
strontium, barium, magnesium or the like, but preferably calcium or strontium)
with a compound of aluminium, to which we add an acid preferably nitric acid.
As an illustration of our method we may use a solution of aluminium acetate and
a solution of calcium nitrate both saturated solutions in the cold; to one ounce
of each we may add one-twentieth of nitric acid but we do not limit ourselves to
these proportions nor to these ingredients as other compounds of these or similar
bases may be efficacious.
When it is desired to clean a stone no matter for what length of time the letter-
ing or design may have been standing upon it, we wash off the old ink with
turpentine. No grinding of any sort is needed, but if the old design has been deeply
etched upon the stone with acid it is best to rub off the relief with snake stone. The
stone having been thoroughly rinsed with water and wiped over, our compound is
now poured upon it and washed well over the whole surface for a minute or two
with a sponge.
The stone is then set upon edge to drain off and dry which it does
very quickly. When dry it will be found to have a beautifully clean surface and
to be very sensitive to the most delicate transfer or drawing. If any special
polishing or graining is required on the stone it should be done before the
application of the compound.
BOULT & WADE,
Agents for the Applicants.

page_text: COMPLETE SPECIFICATION.
Improvements in or relating to the Treatment of Lithographic Stones
and the like.
We, JOSEPH SPEDDING CURWEN, of 8 and 9, Warwick Lane, EC., and Plaistow,
in the County of Essex, Music Printer and Publisher, and ALFRED HERBERT,
c/o J. Curwen & Sons Limited, North Street, Plaistow, in the County of Essex,
Lithographer, 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:-
This invention relates to improvements in the treatment of lithographic stones
and the like, whereby every trace of the old lettering or design is obliterated and
a new and sensitive surface put upon the stone by washing it over with a chemical
solution of special composition, no grinding being necessary.
This solution comprises an admixture of an alkaline earth (such for example
as calcium, strontium, magnesium or the like) or its compounds with a compound
of aluminium in solution to which may be added an acid such as nitric acid.
Two examples of the manner in which the solution may be made up are
follows:
as
To 14 ounces of a saturated solution of alum are added 8 ounces of a saturated
solution of strontium nitrate, and to this mixture may be added 6 ounces of some
acid such as nitric acid, the whole being diluted with 14 ounces of water.
An alternative solution may be compounded as follows:-
An ounce of a saturated solution of aluminium acetate is added to an ounce of
a saturated solution of calcium nitrate, to which may be added the nitric acid
in suitable proportion.
It must be clearly understood that the above stated proportions may be varied.
When it is desired to clean the stone, no matter for what length of time the
lettering or design may have been standing upon it, it is best to first rub off the
relief of the old design with snake stone. The stone having been thoroughly
rinsed with water and wiped over, the above described solution is poured upon
and immediately spread over the whole surface and rubbed well in for a minute
or iwo. The stone is again washed with water and then set upon edge to drain
off and dry, which it does very quickly, when it is ready for use.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. A solution for the treatment of lithographic stones and the like consisting in
the admixture of a compound of aluminium with an alkaline earth or a compound
thereof to which may be added an acid such as nitric acid substantially as
described.
1000