Improvements in Preparing the Surfaces of Lithographic-Stones.
Year: 1895

page_text: Date of Application, 18th Feb., 1895--Accepted, 23rd Mar., 1395
COMPLETE SPECIFICATION.
Improvements in Preparing the Surfaces of Lithographic-Stones.
I, WILHELM WEFERS, of Crefeld, Germany, 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 :-
The object of this improved process for preparing the surfaces of lithographic
stones is to make the stones last longer, and to fit them for new work by using the
utmost care so as not to take off more than is absolutely necessary from the
surface of the stone, the first condition being that the stone be free from fat and
that in its upper layers no acids nor the effect of them shall be present.
In operating the stone for the purpose of removing drawings, lettering or other
previous work, it is first treated with a solution of 80 to 100 grammes of clarified
carbonate of potassa in 9 litres of water spread over the surface of the stone, after
which it is ground with pumice stone and fine sand for a short time.
The carbonate of potassa solution causes the removal of the greases of the old
drawings or other previous work from the stone, while being ground with pumice
stone, so effectually that any remaining portions which may be still held by the
stone, cannot be of any serious consequence to the next work placed thereon.
- The stone is next washed over, and then further treated with a solution
consisting of 200 grammes of chloride of iron in 5 litres of water, which is applied
with a flat paint brush and slowly spread over the stone for one or two minutes
and the stone is then finely ground, without washing off the solution.
The surface of the stone, consisting of carbonate of lime and oxide of iron
(carbonic acid being developed) will settle in the shape of a fine powder, as soon
as the chloride of iron comes in contact with the stone.
This powder serves as a grinding material, and enables a better and quicker
finishing of the stone to be obtained.
This process imparts to the stone a much greater capacity for absorbing fat
than is the case with the usual processes of grinding off with water or other
methods.
The other advantages of this new process consist in not requiring one half the
time, as compared with the old processes for preparing the stone for new work,
thus saving time, stone, and grinding material, and further in the greater safety
and assurance with which the lithographer can operate, securing more beautiful
prints, and durable drawings, permitting 20,000 or more perfect copies to be
pulled off.
The stone needs to be ground off so little that the design may still be visible
and appear raised on the stone, and yet the new prints will pull off in a perfect,
sound, and absolutely faultless condition.
Having now particularly described and ascertained the nature of my said inveu-
tion, and in what manner the same is to be performed, I declare that what I
claim is:-
1. An improved process for removing from the surface of lithographic stones,
previous drawings or other work thereon, by means of covering the surface of the
stone with a liquid solution of carbonate of potassa, and of grinding or rubbing
down the same with pumice stone or fine sand, then washing it and afterwards

page_text: brushing it over with a solution of chloride of iron in water, and finally by nicely
finishing off the surface of the stone without first washing the same, substantially
as herein set forth and described.
Dated this 18th day of February 1895
REGINALD W. BARKER,
Applicant's Agent.