IMPROVEMENTS IN THE PREPARATION OF OXIDE OF ZINC AND IN ITS MANUFACTURE INTO PAINT
Year: 1878

page_text: LETTERS PATENT to William Blanford, of Old Ford, in the County of Mid-
dlesex, Engineer, for the Invention of "IMPROVEMENTS IN THE PREPARATION
OF OXIDE OF ZINC AND IN ITS MANUFACTURE INTO PAINT."
Sealed the 22nd April 1879, and dated the 31st October 1878.
PROVISIONAL SPECIFICATION left by the said William Blanford at the Office
of the Commissioners of Patents on the 31st October 1878.
WILLIAM BLANFORD, of Old Ford, in the County of Middlesex, Engineer.
"IMPROVEMENTS IN THE PREPARATION OF OXIDE OF ZINC AND IN ITS MANUFAC-
TURE INTO PAINT."
"
It is universally known that white lead, both in its manufacture and use as a
pigment, causes serious injury to health, hence it has been the aim for many years
past to introduce "zinc white as a substitute, it being perfectly innocuous and far
superior to white lead in whiteness and durability, but being deficient in what is
technically known as body" or covering properties its use as a pigment has been
very limited.
65
Oxide of zinc, or as it is sometimes called flowers of zinc or white of zinc, whether
made direct from the metal spelter or from the ores of zinc, is more than twice the
bulk, weight for weight, of white lead, and when ground with the same kind of oil
that is used for white lead it still retains its lightness and thinness, and is of nearly
the same bulk as it was before being ground.
This want of "body" has seriously retarded its introduction into general com-
mercial use as a substitute for white lead, and various methods have been tried for
increasing its density, such as mixing it with white lead, or barytes or other sub-
stances commonly used to reduce the cost of the pigment, but the use of all these
has been abandoned, as it was found that the lead or heavy ingredients separated
from the zinc and sunk to the bottom of the cask, leaving the zinc with an undue
proportion of oil at the top, and almost of the consistency of cream.

page_text: It was also found that when oxide of zinc was mixed with lead or other substances
as adulterators the paint dried in streaks, the zinc retaining all its whiteness, and
the lead and other substances gradually darkening into well marked lines.
If used however without any admixture or adulteration zinc paint is prefered to
white lead for its superior whiteness and durability. If exposed to the atmosphere
or subjected to the influence of sulphuretted hydrogen or other deleterious gases it
retains-its-whiteness.-White-lead-would-be-discoloured_in_a_short time; indeed it
is admitted by all that both for interior and exterior use it will last thrice as long
as white lead:
--
Various attempts have been made to give to it the one thing wanting, viz., "body."
Heating in a furnace and suddenly cooling, rolling by conical and other inetal rollers
as in a pugmill were all found ineffectual, and abandoned. Other attempts-were
made by compressing within a holder or cylinder, by hydraulic pressure, notably
"Titterson's" process." This achieved the object of obtaining "body," but the great
compression caused the particles of zinc to cohere, and it was delivered from the
conical holder in sugar-loaf shapes of the hardness of chalk, requireing special
machines for breaking it up and grinding in a dry state and sieving. It was then
almost useless for paint purposes, as the original fineness or smoothness of the zinc
was lost, and the process consequently was abandoned.
The object of this Invention is the treatment by special machinery of the oxide
of zinc of commerce before grinding with oil, so that when ground as a paint it
shall be as heavy and dense as white lead without the use of any other ingredient
or adulterating substance, and yet retaining all the fineness and smoothness charac-
teristic of ordinary oxide of zinc.
For this purpose I use a set of circular stones about 6 feet in diameter, and
inade of the hardest granite, so that no particle of grit can be worn or broken off
in use.
These stones are made, to travel in a restricted circle upon a bed plate made of
the same kind of granite, with bevel gearing so adapted that the stones while
revolving on their axis turn or twist upon their periphery while travelling in a
circle on the bed plate and in the vertical shaft through which the axis of the stones
passes. There is a slot which gives play for the stones to rise or fall, and by this
continued rolling and crushing motion all the air is expelled from the light elastic
particles of oxide, which is reduced in bulk more than one-half, and so dense that
it then has about the same gravity as white lead or barytes. Notwithstanding the
great pressure to which the oxide is submitted by this process it is still in a state of
friable cake-like powder. The oxide is then placed in a suitable cylinder of zinc
metal, with a very fine sieve or mesh driven by steam or other power, which prepares
it ready for mixing tubs which are fitted with metallic blades or flanges which
revolve on an upright shaft within the tubs, which cause the oxide to be thoroughly
mixed with the oil before it is put through ordinary zine grinding mills for conversion
into paint.
Oxide treated by this process will readily admit of admixture with barytes and
other substances without the objections before mentioned, so that the price of zinc
paint can like that of white lead be regulated to meet the demand for any class of
work, which is not at present the case.

page_text: "
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said William Blanford in the Great Seal Patent Office on the 28th
April 1879.
WILLIAM BLANFORD, of 2, Medway Road, Roman Road, Old Ford, in the County
of Middlesex, Engineer. "IMPROVEMENTS IN THE PREPARATION OF OXIDE OF ZINC
AND IN ITS MANUFACTURE INTO PAINT.".
It is universally known that white lead, both in its manufacture and use as a
pigment, causes serious injury to health, hence it has been the ain for many years
past to introduce "zine white" as a substitute, it being perfectly innocuous and far
superior to white lead in whiteness and durability, but being deficient in what is
technically known as "body" or covering properties its use as a pigment has been
very limited.
Oxide of zinc, or as it is sometimes called flowers of zinc or white of zinc, whether
made direct from the metal spelter or from the ores of zinc, is more than twice the
bulk, weight for weight, of white lead, and when ground with the same kind of oil
that is used for white lead it still retains its lightness and thinness, and is of nearly
the same bulk as it was before being ground.
This want of "body" has seriously retarded its introduction into general com-
mercial use as a substitute for white lead, and various methods have been tried for
increasing its density, such as mixing it with white lead or barytes, or other sub-
stances commonly used to reduce the cost of the pigment, but the use of all these
has been abandoned, as it was found that the lead or heavy ingredients separated
from the zinc and sunk to the bottom of the cask, leaving the zinc with an undue
proportion of oil at the top, and almost of the consistency of cream.
+
It was also found that when oxide of zinc was mixed with white lead or other
substances as adulterators the paint dried in streaks, the zine retaining all its
whiteness, and the lead and other substances gradually darkening into well marked
lines. If used however without any admixture or adulteration zinc paint is pre-
ferred to white lead for its superior whiteness and durability. If exposed to the
atmosphere or subjected to the influence of sulphuretted hydrogen or other deleterious
gases it retains its whiteness, while lead would be discolored in a short time;
indeed it is admitted by all that both for interior and exterior use it will last thrice
as long as white lead.
Various attempts have been made to give to it the one thing wanting, viz.,
body." Heating in a furnace and suddenly cooling, rolling by conical and other
metal rollers, as in a pugmill,.&c., were all found ineffectual and abandoned. Other
attempts were made by compressing within a holder or cylinder by hydraulic
pressure, notably Tetterton's process.
This achieved the object of obtaining " body," but the great compression caused
the particles of zinc to cohere, and it was delivered from the conical holder in
sugar-loaf shapes of the hardness of chalk, requiring special machines for breaking
it up and grinding in a dry state and sieving. It was then almost useless for paint
purposes, as the original fineness or sinoothness of the zinc was lost, and the process
consequently was abandoned.
The object of this Invention is the treatment by special machinery of the oxide
of zinc of commerce before grinding with oil, so that when ground as a paint it
shall be as heavy and dense as white lead without the use of any other ingredient
or adulterating substances, and yet retaining all the fineness and smoothness charac-
teristic of ordinary oxide of zinc.
For this purpose I use a set of circular stones about 6 feet in diameter and about
18 inches wide, and made of the hardest granite, so that no particle of grit can be
worn or broken off in use. These stones are made to travel in a restricted circle upon
a bed plate of about the same diameter as the stones, and made of the same kind of
granite, by means of bevel gearing so adapted that the stones while revolving on

page_text: In one vertical shalt through which the axis of the stones passes there is a slot
which gives play for the stones to rise or fall.
By this continued rolling and crushing motion all the air is expelled from the
Flight elastic particles of oxide, which is reduced-in-bulk-more-than-one-half-and-it
then has about the same density as white lead or barytes.
Notwithstanding the great pressure to which the oxide is submitted by this
process it is still in a state of friable cake-like powder. The oxide is then placed
Lin.an_oblong_cylindrical_sieve of convenient dimensions made of zinc metal, and
having a fine mesh. This sieve can be driven by steam or other power. The oxide
after passing through the sieve is ready for the mixing tubs, within which are
metallic blades or flanges fitted at a suitable angle on an upright shaft, which is
kept constantly revolving by bevel gearing, and causes the oxide to be thoroughly
mixed with the oil before it is put through ordinary zinc grinding mills for conver-
sion into paint. Oxide of zinc treated by this process will readily admit of
admixture with barytes and other substances without the objections before men-
tioned, so that the price of zinc paint can like that of white lead be regulated to
meet the demand for any class of work, which is not at present the case.
Having now described the nature of the said Invention and the manner of per-
forming the same, I declare that I claim, the mode of treating or densifying oxide
of zinc, and preparing the same ready for grinding with oil, as herein set forth.
In witness whereof, I, the said William Blanford, have hereunto set my hand
and seal, this Twenty-fourth day of April, in the year of our Lord One
thousand eight hundred and seventy-nine.