IMPROVEMENTS IN THE MANUFACTURE OF TABLETS FOR WRITING OR DRAWING
Year: 1880

page_text: LETTERS PATENT. to Charles Denton Abel, of No. 28, Southampton
Buildings, Chancery Lanc, in the County of Middlesex, for an Invention
of "IMPROVEMENTS IN THE MANUFACTURE OF TABLETS FOR WRITING OR
DRAWING." A communication from abroad by Emanuel Thieben, of Pilsen,
in the Austrian Empire.
PROVISIONAL SPECIFICATION left by the said Charles Denton Abel at the
Office of the Commissioners of Patents on the 16th November 1880.
CHARLES DENTON ABEL, of No. 28, Southampton Buildings, Chancery Lane, in
the County of Middlesex. "IMPROVEMENTS IN THE MANUFACTURE OF TABLETS
FOR WRITING OR DRAWING." [A. communication from abroad by Emmanuel
Thieben, of Pilsen, in the Austrian Empire.]
According to this Invention white cement and mastics are employed for forming
tablets to receive writing or drawing. Among the materials available for the
purpose are porcelain clay with Spanish white, cements or mnastics prepared from
inagnesia and its compounds, such as magnesite with magnesium chloride or
muriatic acid; also cement or plaster of gypsum with alum and borax, zinc oxide
made up with solution of zinc chloride, Spanish white, baryta, or caesium, with
solutions of silicate of soda or potassa. The materials being mixed with water
the mixture is cast into moulds, pressed, and afterwards smoothed or ground, and
the surface may be hardened by impregnating it with silicate solutions; or such
solutions may be used instead of water for forming the mixture. After hardening
the tablets are fixed in suitable frames. The mixture instead of being cast in
moulds may be applied in a pasty condition to any desired surface, such as paper
or other fabric, slate, or cement. When coloured tablets are desired a suitablo
pigment is introduced into the cement or mastic mixture, or it is merely applied
to the surface thereof. Tablets prepared as above described may be used with
advantage instead of slate or graphite boards, being less injurious to the eye than
dark surfaces, and as they can be made of any desired form and size they are
available for educational purposes, either for use by scholars or for hanging to
walls of class rooms or otherwise.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Charles Denton Abel in the Great Seal Patent Office on the
13th May 1881.
"
CHARLES DENTON ABEL, of No. 28, Southampton Buildings, Chancery Lane, in
the County of Middlesex. IMPROVEMENTS IN THE MANUFACTURE OF TABLETS
FOR WRITING OR DRAWING." A communication from abroad by Emanuel
Thieben, of Pilsen, in the Austrian Empire.
According to this Invention white cements and mastics are employed for forming
tablets to receive writing or drawing. Among the materials available for the
purpose are porcelain clay with Spanish white, cements or mastics prepared from
imagnesia and its compounds, such as magnesite with magnesium chloride or
muriatic acid; also cement or plaster of gypsum, alum, and borax, zinc oxide made
up with solution of zinc chloride or muriatic acid.
The mode of producing the tablets is as follows:-The cement is ground to a
fine dowder, and is moistened with water to the extent of about one part of water
to from 8 to 10 parts of cement. In order to effect the moistening in a perfectly
uniform manner it is preferred to treat the cement in a disintegrator. If desired
white powdered minerals, such as quarz and marble, may be added to the extent
of about one third of the entire quantity. The mixed material is deposited direct
from the disintegrator into a mould for the tablets, in which it is rendered
uniformly level by any suitable apparatus. In the moulds are placed in the first
instance polished ebonite plates, and a similar plate is also placed on top of the
material as a cover, partly in order to overcome the difficulty of removing very
thin tablets (which may be under th inch thick) from the mould, and partly to
obtain perfectly smooth surfaces.
The moulds so prepared are then subjected to considerable pressure in order to
obtain perfectly coherent and dense tablets. The pressure employed should be
about 27000 lbs. on the square inch. The tablets thus produced are further
moistened with water by means of a spray apparatus, and after from 3 to 4 hours,
when they will have attained the required consistency, they are soaked in water
and are placed in a cool locality to harden.
For producing tablets from inagnesia cement the magnesia or magnesite must be
pure and finely ground, and is mixed by means of a disintegrator with a magnesium
chloride solution of 20° to 30° Beaumé, or with muriatic acid diluted to the extent
of one half the quantity of water. The proportions employed should be about
from 8 to 10 parts by weight of magnesia with 1 part of magnesium chloride or
muriatic acid solution. With the magnesia or magnesite may be mixed white
minerals, such as quarz and marble, to the extent of about one half the quantity.
The method of manufacture is otherwise the same as above described.
In using mastics the following process is employed:-Zincoxide that has been
subjected to a red heat is mixed by means of the disintegrator with a concentrated
solution of zinc chloride of from 40° to 50° Beaumé, or with muriatic acid diluted
to the extent of one half of water in the proportion of about 8 to 10 parts by
weight of zincoxide with one part of zinc chloride or of dilute muriatic acid. The
other part of the process is the same as before described, with the exception of the
use of water. In this case also finely ground quarz, marble, &c., may be admixed
to the extent of about one half the quantity.
For producing colored tablets the raw materials are previously colored of the
required tint, or the tablets themselves may be steeped in the fluid dye and be
then rubbed over with oil. For colored tablets may also be used Roman and
Portland cement. The tablets may also be produced by making liquid mixtures
of the beforementioned cements or mastics, the cements being mixed with water,

page_text: and the magnesia cements and mastics with solutions of magnesium chloride or
zinc chloride, or muriatic acid, to a semi liquid consistency, after which the mass
is treated in a filter press until the tablets made therefrom attain the consistency
of leather; these tablets are then pressed perfectly smooth between ebonite plates
by means of a high degree of pressure, after which they are left to harden; or
according to another method the substance is made of such a consistency that it
can be spread on to paper, canvas, sheet metal, or wood, the surface of which is
first coated with glue or gum; the surface of the substance is then smoothed by
rollers. The above described writing tablets may be made of any desired form or
size, according to the purposes for which they are intended, and they may be fixed
or moulded upon bases or foundation of any suitable material; they can also be
ruled with lines for use in schools.
Having thus described the nature of this Invention, and in what manner
the same is to be performed, as communicated to me by my foreign correspondent,
I claim,―
The herein described improved manufacture of white or colored tablets for
writing or drawing from cements and mastics.
In witness whereof, I, the said Charles Denton Abel, have hereunto set my
hand and seal, this Thirteenth day of May, in the year of our Lord One
thousand eight hundred and eighty one.
CHAº. D. ABEL. (L.S.)