Improvements in the Liquid Material or Slip" used in the Manufacture of Porcelain, Stoneware and the like.
Year: 1891

page_text: Date of Application, 22nd Oct., 1891-Accepted, 28th Nov., 1891
COMPLETE SPECIFICATION.
66
Improvements in the Liquid Material or Slip" used in the
Manufacture of Porcelain, Stoneware and the like.
A communication to me from KARL GOETZ, of Karlsbad, in the Empire of
Germany, Doctor.
I, EDMUND EDWARDS, of the firm of Edwards and Co., Patent Agents and
Engineers, of 35, Southampton Buildings, Chancery Lane, in the County of
Middlesex, 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, that is to say :-
Whilst by the ordinary process the liquid or "slip " for making, by pouring it
into moulds, articles of porcelain, stoneware, and the like, is so prepared that the
mass prepared and kept for use has to be mixed with about one and a half parts of
water in order to make it sufficiently fluid for pouring, by the process which forms
the subject of the present invention the mass is mixed with an aqueous solution of
carbonate of soda, bicarbonate of soda, or calcined soda or soda ash, and is thereby
made sufficiently fluid and fit for pouring.
The use of the calcined soda or soda ash ensures a porcelain of pure white colour. It
is quite sufficient to add to 1500 parts by weight of the porcelain mass about 1 part by
weight of the concentrated solution, selecting the proportion most suitable to the
mass, for stoneware and earthenware a little additional water being necessary.
In order to prevent the swellings and grey colour which are sometimes produced
upon articles of porcelain, especially at their edges, during the process of burning,
it is advisable to add to the aqueous solution sufficient cinnabar to give to the entire
solution a delicate but very weak rose tint.
The mixture or "slip" prepared in the manner described, although the large
quantity of water present in the mixture as ordinarily used is absent, is nevertheless
more fluid than the latter, contains no air bubbles, flows into the extreme parts
and into all the narrowest and smallest details of the mould, and allows the manu-
facture in this way of articles which hitherto could not be formed by pouring the
material into moulds, but had to be turned or shaped separately, as for instance
reliefs or large oval dishes or vessels.
Moreover a separate mould was necessary for each part, as for instance for a
coffee pot, three moulds would be necessary that is to say one for the body, one for
the handle, and one for the spout. By the present improvements the possibility of
manufacturing porcelain and earthenware goods by pouring is so extended that a
quicker and at the same time better production is possible.
An ordinary workman can produce by using this invention at least six hundred
large dishes or vessels in a week, whilst a clever and experienced turner can at the
outside make from 150 to 160 in the same time.
The articles produced by the improved method are of much more uniform quality
and density, more solid, stronger, and less liable to break, than those made from
ordinary material or "slip," or than those turned or finished separately.
Whilst by the ordinary process the mould can at most be used three times in
succession and then requires to be dried, by the use of the new soda material
the mould can be used 10 to 12 times, and can then be dried very much more
quickly.
For this reason the troublesome drying plant for the mould is greatly reduced, and
injury to the moulds themselves is also largely prevented.
Consequently for a new factory a smaller stock of moulds than usual is necessary
in the first place, and the consumption of this stock is also considerably reduced as
compared with the present system.

page_text: Moreover the contraction which takes place during the burning of the articles
and which with the ordinary mixture or "slip" prepared with water is in about the
proportion of from 5 to 4 or from 6 to 5, is greatly reduced and unimportant.
Articles prepared by the improved process do not require a heat in the oven, as
hitherto, of from 1750 to 1800 degrees, but of only about 1600 degrees. Moreover
the mass need not be ground for more than 16 hours, and may be at once prepared
with the carbonate of soda-or soda-solution, whilst by the old process 22 to 24
hours grinding is necessary and a subsequent much longer storing of the mass.
By the use of the new process ornamentation by burned-in colours can be readily
applied.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
-
The process for the preparation of the mixture or "slip" for making porcelain,
stoneware, earthenware, and the like, consisting in the mixture of the mass with an
aqueous solution of carbonate of soda, or bicarbonate of soda, or calcined soda,
or soda ash, with or without the addition of cinnabar, substantially as described.
Dated the 22nd day of October 1901.
EDWARDS & Co.,
35, Southampton Buildings, London, Agents for the Applicant.