IMPROVEMENTS IN DRESSING MILLSTONES, AND IN MATERIALS EMPLOYED THEREIN
Year: 1862

page_text: PROVISIONAL SPECIFICATION left by Richard Archibald Brooman at
the Office of the Commissioners of Patents, with his Petition, on
the 14th October 1862.-A communication from abroad by Cyprien
Marie Tessié du Motay and Charles Raphael Maréchal, both of Metz,
France.....
I, RICHARD' ARCHIBALD BROOMAN, of 166, Fleet Street, in the City of
London, Patent Agent, do hereby, declare the nature of the said Invention
for "IMPROVEMENTS IN DRESSING MILLSTONES, AND IN MATERIALS EMPLOYED
THEREIN," (communicated to me from abroad by Cyprien Marie Tessié du Motay
and Charles Raphael Maréchal, both of Metz, France,) to be as follows:-
Hitherto millstones have been dressed by mechanical means. Now this
Invention consists in dressing millstones as hereafter described by the action
of hydrofluoric acid on the siliceous matter of which they are composed. I
cover by hand or by printing those parts of the surface of the stone which are
not to be eaten out with an ink or varnish not acted upon by hydrofluoric acid.
Into the spaces not covered by this ink or varnish I pour hydrofluoric acid,
which acting on the siliceous matter of the stone dissolves it and bites out
those parts, not protected.
I now proceed to describe the composition and modes of employment of the
inks and varnishes.
Composition. The varnish may be composed of wax, pitch, bitumen,
essence of turpentine, spermaceti, mastic, or any other resinous substance,
mixed together in proportions varying according to the viscosity or fluidity
which it is desired the varnish should possess. The essence of turpentine
may be replaced by benzine, essence of lavender, or any other essence.

page_text: 7
Instead of this varnish the soft varnish employed in engraving by means of
aquafortis may be used. The ink, which should be printed on paper and trans-
ferred afterwards to the millstone, may be composed of various substances, such
as tallow, wax, stearic acid, palmistic acid, paraffin, raw or boiled linseed oil,
resin oil, bitumen, pitch, spermaceti, mastic, or other resinous substance, essence
of turpentine, benzine, essence of lavender, or other essence, gutta percha,
caoutchouc, and generally any fatty or resinous substance, coal, sulphate of
lime, fluoret of calcium, or any other substance easily reduced to an impalpable
powder and not attacked by hydrofluoric acid may be employed to give
plasticity to the composition.
The following inks composed of the substances above named have been found
to answer well:-
Ink A.
Powdered Judea bitumen
Stearic acid
Essence of turpentine
Ink B-Powdered Judea bitumen
Stearic acid
Essence of turpentine or benzine
Resin
about 300 parts,
200
"
"
300
"
about 300 parts,
200
"
"
300'
"
"
'100
"
"
In these inks, A and B, palmistic acid or paraffin may be substituted for.
the stearic acid; a little tallow or wax should be added according to the tem-
preature of the season to render the ink more or less liquid.

page_text: Denzine
Resin oil
Resin
140
"
}}
mixed together
50
"
"
50
"
"
Boiled linseed oil (very viscous)
100
"
"
100'
"
"
20
"
"
Plaster
Coal
Those inks which contain plaster, coal, or any substance not fatty or resinous,
should be pounded very finely in a mortar. To facilitate this operation, benzine,
essence of turpentine, essence of lavender, or other essence, raw linseed oil,
fatty oil, or resin oil, may be added to the inks. The proportions before given may
be varied considerably according to the time of year and other circumstances.
Modes of employment.-The transfer paper and the processes of prin-
ting employed in pottery and lithography may be made use of with the
inks before described. Numerous substances serve for the preparation of the
paper, such as gum, dextrine, honey, sugar, gelatine, starch, paste, alum,
silicate of soda, and soap, employed separately, mixed or in succession. Tho
feature of these various preparations consists in covering the paper with one
or several coats which will render it impermeable to the ink, and which may
be dissolved or removed easily from the paper by the action of water, acidulated
or not. For inks A and B, thin paper without any preparation will suffice by
taking the precaution to wet the reverse side with acidulated water, to heat it
for a moment, at a temperature of from 75° to 110° Fahrenheit, and to apply
it damp on the millstone. For inks C, D, and E, and similar inks, the printed
paper should be applied dry on the millstone; in this case it is necessary to
employ paper such as is used in autography, and lithography, or soaped paper
or other paper used in pottery, or paper previously saturated with a solution
of alum and silicate of soda, and afterwards coated with a thin coating of soap.
The varnishes can be employed in several ways; they may be applied by a pen,
brush, or otherwise. The varnish may be spread evenly over the parts of the
stone to be bitten out; a dry-pointed instrument, a stile, or tracing machine
may then be used to remove from the stone the varnish covering those parts
of the stone which are to be eaten out by the hydrofluoric acid in the same
manner as in engraving with aquafortis.