AN IMPROVED METHOD OF PREPARING ABSORBENT PAPER TO BE USED IN THE PROCESS OF COPYING LETTERS
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by Adolf Gutensohn at the Office of the
Commissioners of Patents on the 17th July 1882.
ADOLF GUTENSOHN, of 40, Southampton Buildings, in the County of Middlesex
"AN IMPROVED METHOD OF PREPARING ABSORBENT PAPER TO BE USED IN THE
PROCESS OF COPYING LETTERS
"
My invention has for its object an improved method of preparing absorbent
paper, so that when damped or moistened with water it can be used for the
purpose of transferring sufficient moisture to ordinary transparent copying paper,
so that the latter is capable of receiving under pressure a copy of letters or other
manuscript or designs written in copying ink. By the use of my invention, it is
unnecessary to damp such transparent copying paper in the ordinary way by
means of a brush and it is consequently preserved from injury, whilst by the
improved method of preparing the absorbent paper as hereinafter described it
becomes tough, durable, and not liable to become torn or injured when damp,
whilst its absorbency remains unimpaired.
In order to put my invention in operation, I take a solution of chloride of zinc
prepared by immersing metallic zinc in commercial muriatic acid diluted with an
equal quantity of water.
When the action of the muriatic acid has ceased, the liquid is filtered and any
iron which may be present is removed by adding chloride of Lime, care being
taken that it is not in excess, and the oxide of iron thus formed is skimmed off.
The chloride of zinc thus prepared is added gradually to liquid ammonia until
the latter is saturated.
I also take a solution of nitrate of zinc prepared in the same way as the chloride
of zinc, except that the process for the removal of iron is not necessary, and the
nitrate of zinc is concentrated and any free nitric acid removed.
The nitrate of zinc is dissolved in ammonia as long as the latter is capable of
taking it up.
Of the two ammoniacal solutions thus prepared I take five parts of that first
described containing chloride of zinc, to which I add one part of the other con-
taining nitrate of zinc, and I add about one half per cent of a strong solution of
glue or gelatine.

page_text: To this compound solution I add a small quantity of oxide of zinc until the
solution becomes milky, and I then coat both sides of any suitable absorbent paper
with it, or I immerse the paper into it.
The paper is then dried and ironed either with a hot flat iron or by passing it
between heated rollers after which it is ready for use.
Instead of treating ordinary paper in the method described, a sufficient quantity
of oxide of zinc of high specific gravity may be mixed with the paper pulp during
the process of manufacture, and the paper when made is immersed in a solution of
chloride of zinc in water or ammonia. The paper is then finished in the way
already first described.
Absorbent paper prepared as described according to my invention may be used
by damping it and then placing it above the transparent copying paper which is
placed upon the letter or other document which is to be copied in an ordinary
copying press; or a sheet of the transparent copying paper may be placed upon the
letter or manuscript on any flat surface and the damped absorbent paper prepared
as described being placed above the former, is pressed down by hand, with sufficient
force to obtain the required copy.