Improvements relating to the Manufacture of White Lead for White Lead Paint.
Year: 1895

page_text: Date of Application, 14th Dec., 1895
Complete Specification Left, 14th Sept., 1896-Accepted, 7th Nov., 1895
PROVISIONAL SPECIFICATION.
Improvements relating to the Manufacture of White Lead for White
Lead Paint.
I, CHARLES DAGLISH ISMAY of Ouseburn Lead Works in the City and
County of Newcastle-on-Tyne Manufacturer do hereby declare the nature of this
invention to be as follows:-
This invention has reference to improvements relating to the manufacture of
white lead and has for its object the more effectual or complete removal or
separation of the water which hitherto has remained after the process of
"pugging" has taken place. In this process the white lead mixed with water has
oil added to it and the whole is thoroughly agitated in a pugmill where the bulk
of the water is separated but a certain quantity has always bitherto remained
which has been carried forward in the material to the next or grinding process
which has hitherto consisted in passing the material through or between solid
granite or other stones or rolls.
To get rid of the water thus held in the white lead J propose to construct
hollow rolls in metal and to introduce steam hot air or equivalent fluid thereto for
example through the trunnions or otherwise as found desirable for the purpose of
heating the rolls and so driving off the water during the grinding process and in
the event of this involving too extensive a system of hot rolls propose to
distribute the heating process by steam or otherwise jacketting the pugmill so as
either to drive off the whole of the water thereat or partially so the remainder in
such case being subsequently evaporated at the steam or hot-air-heated rolls as
above foreshadowed or I may aid the evaporation at the pugmill or subsequently
if found desirable by subjecting the material or vessel being heated to a vacuum
and thus enable me to better regulate the temperature employed.
Dated this 13th day of December 1895.
A. CRAWHALL CHAPMAN,
St. Nicholas Buildings, Newcastle-on-Tyne, Patent Agent.
Improvements relating to the Manufacture of White Lead for White
Lead Paint.
I, CHARLES DAGLISH ISMAY, of Ouseburn Lead Works, in the City and
County of Newcastle-on-Tyne, Manufacturer, do hereby declare the nature of this
invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement :-
This invention relates to the manufacture of white lead which has to be mixed
with oil for conversion into white lead paint, and has for its object the effectual
and complete removal or separation of the water which has hitherto remained in
the material and also to avoid stove heating and as far as possible the handling of

page_text: the material by the operatives which operations are the most dangerous and
insanitary.
Hitherto in the manufacture of white lead for white lead paint the lead pulp has
been dried to powder, which process is objectionable and dangerous, and by my
invention I dispense with it entirely.
In another process, the lead pulp with its contained water is mixed with oil in a
pugmill and the whole thoroughly incorporated. By these means the bulk of
water is separated and discharged, but a certain quantity has necessarily been
carried forward in the material (which is most deleterious thereto) to the next or
grinding process which consists in passing the mixture between solid granite or
other stones or rolls.
According to my present improvements, in getting rid of the water held, as
stated, in the white lead I drive it off wholly or as far as possible during the
process of mixing the white lead and the oil in the pugmill, and this I effect by
employing a pugmill capable of being closed air-tight and provided with a heating
jacket wholly or in such degree as may be required; in the pan of this the water-
charged lead and oil are well mixed and incorporated by agitation, heat being
applied with advantage during the process, and the water, freed by the combination
of the lead and oil, rises to the surface and is discharged by suitably disposed
exits.
I find it advantageous to aid the evaporation produced in the pan of the pugmill
by subjecting the material therein during the evaporation to a vacuum or partial
vacuum which may readily be effected by connecting the closed pan to a vacuum
pump or condenser in the known way. Then the pan being closed up, steam, hot
air, or equivalent heated fluid is admitted to the jacket by a pipe from the boiler
or hot fluid generator at such a pressure as to raise the contents of the pan to a
temperature which will vary with and be regulated by the vacuum obtained, but
which must not in any case be such as to damage the lead and which may be for
example from 150° to 250° Fahr. The agitation and heating of the mass are
simultaneously conducted and continued until all or as much water as practicable
has been evaporated therefrom, and subsequently the dried product may be
conveyed from the pan in any convenient manner to the final grinding rolls. In
order to ensure that no water remains these rolls may be constructed of hollow
metal and supplied with steam or hot air for example through the trunnions so as to
ensure a further drying by evaporation in and during the grinding process, but this
final heating and evaporating is seldom necessary.
In performing my invention it will be seen that the only apparatus needed is a
suitably jacketed pugmill capable of being closed, a vacuum producing appliance,
and sometimes hollow metal rolls, and the construction and arrangement of these
together with the various steam or equivalent and vacuum pipes and connections,
valves, and so forth will be readily understood and could be easily constructed by
those skilled in the art in a great variety of ways, and hence illustration by drawings
is not necessary.
From the above it will be seen that by my invention the conversion of white lead
into white lead paint is effected without the necessity of stove drying, and as far as
possible handling of the material with its consequent prejudicial effects on the
operatives is avoided, and at the same time the finished article is of a superior
quality and is produced much more cheaply.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what
I claim is :-
1. The improved method or process for manufacturing white lead for white lead
paint without stove drying conducted substantially in the manner and for the
purposes herein before described.
2. In the manufacture of white lead for white lead paint with the object of
getting rid of contained water mixing the lead pulp and oil in a pugmill provided

page_text: with a heating jacket, and after the mixing is effected and as much water as
possible run off, closing the pugmill pan and subjecting the mixture therein to the
combined evaporating influences of heat and vacuum and subsequently if required
passing the product through hot metal rolls, substantially as herein set forth.
3. In the conversion of white lead into white lead paint the use of apparatus
such as is above referred to adapted to operate in the manner hereinbefore
described.
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