IMPROVEMENTS IN TABLETS FOR ERASABLE WRITING KNOWN AS ERASABLE TABLETS,' AND IN THE COMPOUNDS KNOWN AS WHITE SLATING FOR PREPARING SUCH TABLETS
Year: 1879

page_text: LETTERS PATENT to Arthur William Lovell Reddie, of the Office for Patents,
66, Chancery Lane, in the County of Middlesox, Patent Agent, for the
Invention of "IMPROVEMENTS IN TABLETS FOR ERASABLE WRITING KNOWN
AS ERASABLE TABLETS,' AND IN THE COMPOUNDS KNOWN AS WHITE
SLATING FOR PREPARING SUCH TABLETS." A communication from abroad by
Henry Wells Holly, of Brooklyn, in the State of New York, United States of
America
PROVISIONAL SPECIFICATION left by the said Arthur William Lovell
Reddie at the Office of the Commissioners of Patents on the 30th September
1879.
ARTHUR WILLIAM LOVELL REDDIE, of the Office for Patents, 66, Chancery Lane,
in the County of Middlesex, Patent Agent. "IMPROVEMENTS IN TABLETS FOR
ERASABLE WRITING KNOWN AS ERASABLE TABLETS, AND IN THE COMPOUNDS
KNOWN AS WHITE SLATING FOR PREPARING SUCH TABLETS." [A communication
from abroad by Henry Wells Holly, of Brooklyn, in the State of New York, United
States of America.]
"
The white or nearly white tablets known as erasable tablets and intended for the
reception of writing or drawing in black lead pencil have been commonly prepared
with a coating known as 'white slating," which consists of water-glass and a
metallic oxide added thereto to form a tooth to enable the tablet to take the
pencil freely. Such a compound is inelastic and has a tendency to crack when dry.
To remedy this defect it is now proposed to prepare the slating compound of
water-glass, oxide of zinc, and silicate of magnesium, and to apply this compound
to paper, card board, paste-board, or other suitable material.
The proportions preferred are one (1) quart of water-glass of about thirty nine
degrees (39) Baumé diluted with one (1) quart of water to one (1) pound of pure
oxide of zinc powdered and about one (1) pound of powdered silicate of magnesium.
When thoroughly mixed a compound of the consistancy of paint is formed which
may be readily applied to sheets of stiff paper, board, or other material by means of
a brush or otherwise.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Arthur William Lovell Reddie in the Great Seal Patent Office on the
25th March 1880.
ARTHUR WILLIAM LOVELL REDDIE, of the Office for Patents, 66, Chancery Lane,
in the County of Middlesex, Patent Agent. "IMPROVEMENTS IN TABLETS FOR
ERASABLE WRITING KNOWN AS 'ERASABLE TABLETS,' AND IN THE COMPOUNDS
KNOWN AS 'WHITE SLATING' FOR PREPARING SUCH TABLETS." A communication
from abroad by Honry Wells Holly, of Brooklyn, in the State of New York, United
States of America.
The white or nearly white tablets known as erasable tablets and intended for
the reception of writing or drawing in black lead pencil which is intended to be
rubbed out have been commonly prepared with a coating known as "white slating,"
which consists of a compound of water-glass and a metallic oxide added thereto to
form a "tooth" to enable the tablet to take the pencil freely. Such a compound
is entirely inelastic and it is found that upon drying the slated surfaces are filled
with innumerable fine cracks or fissures into which the lead of the pencil is rubbed
in erasing, thereby in a very short time rendering the tablet unfit for use.
The object of the Invention is to furnish a slating compound for such tablets
having the required degree of elasticity, which compound when spread upon a
surface and dried will form a smooth, even, and unbroken surface of great durability.
To this end the Invention consists, firstly, in a slating compound composed of a
solution of water-glass, oxide of zinc, and silicate of magnesium; and it consists,
secondly, in a tablet made of paper, card board, paste board, or other suitable
material (prepared with such compound).
I take about one (1) quart of water glass of about thirty nine degrees (39°)
Baumé, and add one (1) quart of water. With the solution thus formed I mix
about one (1) pound of pure oxide of zinc powdered, and about one (1) pound of
powdered silicate of magnesium. When thoroughly mixed a compound of the
consistency of paint is formed which may be readily applied to sheets of stiff paper,
board, or other material by means of a brush or otherwise. This compound when
dried forms a smooth, even, and unbroken surface from which pencil or other
marks may be easily erased, and as the said surface contains no cracks or fissures
into which the lead of the pencil can be rubbed, tablets slated with such compound
are very durable, and will not become discolored by long use.
I do not confine myself to the exact proportions herein specified of the ingredients
of which the slating compound is composed, as the proportions might be varied to
some extent without altering the character of the compound.
Having now set forth the nature of the Invention of "Improvements in Tablets
for Erasable Writing known as Erasable Tablets,' and in the Compounds known as
White Slating' for Preparing such Tablets," as communicated to me from abroad,
and explained the manner of carrying the same into effect, I wish it to be under-
stood that I claim,-
First. The slating compound composed of water-glass, oxide of zinc, and silicate
of inagnesium, substantially as herein specified.
Secondly. A tablet made of paper, pasteboard, cardboard, or other suitable
material prepared with a compound of the ingredients herein described.
In witness whereof, I, the said Arthur William Lovell Reddic, have hereunto
set my hand and seal, the Nineteenth day of March, in the year of our Lord
One thousand eight hundred and eighty.