Improvements in and relating to Enamel for Metals, Glass-ware, Earthenware, and other Materials.
Year: 1891

page_text: Date of Application, 11th May, 1891-Accepted, 15th Aug., 1891
Improvements in and relating to Enamel for Metals, Glass-ware,
Earthenware, and other Materials.
I, GUSTAV GEHRING, Mayor of Landshut, in the Kingdom of Bavaria, 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, first, to an improved enamel for use on iron, steel and other
metals, glass-ware, carthenware and similar materials, and, secondly, to a process
for the production of such enamel.
A simple and inexpensive but fine and permanent coloured enamel made accord-
ing to this invention, and suitable for the reception of other coloured enamels,
consists essentially of a powder, the chief constituents of which are graphite, blast-
furnace slag, burnt alum and pulverized coke or similar substance, and a compound
obtained by boiling 100 parts by weight of linseed oil with 5 parts by weight of an
oxide or a borate of lead (for instance, litharge or the corresponding borate). The
constituents of the powder may be mixed in equal proportions or the proportions
may be varied according to taste.
In applying this enamel, the graphite, or the slag, and the coke are mixed with
pulverized crystal glass. This powder is rubbed up with the compound of boiled
linseed oil and oxide or borate of lead, and then spread on the metal. It is after-
wards roasted and melted at a bright red heat. A permanent enamel can thus be
produced on all metals capable of withstanding a red heat; for instance, iron, steel,
copper and silver.
A particularly fine enamel is produced by using powdered graphite, cold-pressed
Hungarian linseed oil and an oxide or a borate of lead; enamel so made being alone
sufficient for the ornamentation of metals, and being easily manufactured and very
cheap.
The colours are burnt in with the aid of the above-mentioned linseed oil
compound, to which turpentine oil may be added. They are mixed, in the form in
which they are known in commerce, with the compound, and are then spread on the
metal and melted in. They become firmly and uniformly fixed on the metal, and
give it a pleasant tone. Moreover, gold, silver, platinum and aluminium can be
melted in with equally good results, so that the process supplies means for the
ornamentation of metals in a variety of ways. A special advantage of the materials
used in this process is that the metals covered with the enamel can be exposed to
a very high temperature without any fear of the enamel being damaged thereby, or
the colours changed. Metals so enamelled, after having been exposed from ten to
fifteen times to a white heat, have preserved their original appearance. The enamel
is, therefore, particularly suitable for covering cast iron stoves.
The linseed oil compound can also be used for enamelling in colours on
earthenware and glassware, and when so applied the compound forms a cheap
substitute for the more costly oils which are at present employed for the
purpose.
Kaolin, when mixed with a flux and rubbed up with water or with linseed oil
boiled with litharge, forms an excellent ground or base enamel for iron, steel and
other metals and earthenware, on which ground or base coloured enamels can be
laid. After laying on and drying the kaolin preparation, the coloured enamels,
rubbed up with the linseed oil compound, can at once be laid on and melted in
without the kaolin base being previously fused. In this way, the process becomes
simpler and cheaper, because one burning is saved. Earthenware goods and
crockery can, if desired, without being previously burnt, as soon as they are

page_text: partly dried, be coated or overlaid with the kaolin enamel rubbed up with water.
If designs be then painted on the dried kaolin ground with refractory enamel
colours rubbed up with the linseed oil compound, the earthenware so treated can be
finished by one burning in the potter's oven; the extra burning involved in the
indirect process being saved. As the kaolin, when not mixed with two large a
quantity of flux, forms a ground of a soft white colour, crockery and earthenware
of every variety of red-, white- and yellow-burning clays, as well as graphite
utensils, can be made uniformly white or white with coloured ornamentation. If
graphite or other crucibles be covered with the kaolin enamel, such crucibles
become more durable and more suitable for many purposes. The use of com-
paratively little water, or linseed oil compound, with the full quantity of kaolin,
gives cast iron an uniform dull white surface, which in many cases enables painting
and enamelling to be dispensed with; but ornamental enamels of soft or brilliant
colours, according to taste, can be melted on. With white background and the now
usual colours of rokoko and baroque, iron stoves, iron fire-places, and iron frame-
work can be made to resemble earthenware or wood.
Mixtures of kaolin and graphite, as well as of kaolin and slag, give peculiar
and pleasing tones, which are permanent after burning. Kaolin and graphite give
brown in various shades. Kaolin and slag give peculiar marble streaks and
grey tints.
This enamel is rendered suitable for various purposes if a comparatively larger
quantity of flux be used with the kaolin. Graphite or slag may also be added. A
very cheap, firm, rust-preventing ground-colour is then produced, which is alone
sufficient in many cases.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed, I claim
1. The improved manufacture of enamel for iron, steel and other metals, glass-
ware, earthenware and similar materials, substantially as herein described.
2. The hercin-described process for enamelling metals, earthenware and glass-
ware, consisting in mixing a powder of graphite, coke, slag, alum and kaolin, or one
or more of these materials with a flux, rubbing up the mixture with a compound
obtained by boiling linseed oil with an oxide or a borate of lead, and laying on,
drying and burning the same.
3. The herein-described process for enamelling metals or earthenware, consisting
in mixing powdered kaolin with a flux, rubbing up the mixture with water, and
laying on, drying and burning the same.
4. In the processes herein described and claimed, applying to the ground enamel
any other coloured enamel, the latter being rubbed up with the linseed oil compound
or other volatile oil or with water, and laid on or melted in either before or after
the burning of the ground enamel.
1
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2001
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Agent for the Applicant.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Agent for the Applicant.