Improved Process of Grinding Colors Employed for Ceramic purposes.
Year: 1899

page_text: Date of Application, 29th June, 1899
Complete Specification Left, 27th Feb., 1900-Accepted, 28th Apr.,
1900
PROVISIONAL SPECIFICATION.
Improved Process of Grinding Colors Employed for Ceramic purposes.
I, EMILE LOUIS LEFRANC, of 18, Rue de Valois, Paris, in the Republic of
France, Manufacturer of Colors, Varnishes, &c., do hereby declare the nature
of this invention to be as follows:-
Colors employed for ceramic purposes are generally composed of one or several
metallic oxides mixed with a flux capable of dissolving them and of giving to
them by roasting, the appearance of a colored enamel.
The vitreous nature of the flux and its chemical composition make the grind-
ing of these colors, an operation so much the more delicate as their extreme
fineness is one of the essential conditions of their good use.
To bring these colors to the desired degree of tenuity, they are made with
water into a paste sufficiently thin that is passed a great number of times
through flint mills or better still porcelain mills.
The product is then drained off, dried and made fairly easily into powder
by the ordinary means.
However, the drying having brought to the surface of the color the soluble
salts of the flux, these latter form thin crystalline crusts which in order to be
reduced to powder, necessitate another operation, generally called second
grinding.
It has been accomplished hitherto by grinding again these substances, either
with oil of turpentine or with a mixture of this latter with oil of lavender.
These liquids do not merely prevent the dissolution of the salts above men-
tioned they leave in the color, in consequence of their partial oxydation, a
variable resinous residue which will consequently facilitate the incorporation
of the powder with the fatty oil, which is the vehicle preferred to dilute these
colors.
The employment of the oils of turpentine and lavender for the second grind-
ing does not present any inconvenience when the powders are to be used
immediately. On the contrary, if they are kept for a longer or shorter time,
the oxydation of the resinous product is completed and it becomes almost
insoluble in the fatty oil and consequently produces a paste which is worked
with difficulty by the brush.
To prevent these inconveniences I have sought :-
1st. For the grinding, a liquid completely volatile, upon which the air has
no action and which moreover is not a solvent of the matters composing the flux.
2nd. To facilitate the mixing of the powder with the fatty oil a product
soluble in this oil and upon which the air has likewise no action.
I have found in the fractional distillation of petroleum, liquids responding
entirely to my requirements.
I employ for grinding, the portions which distil between 140° and 160° C.
The choice of this temperature is not absolutely fixed; a petroleum having a
boiling point less elevated might answer the purpose, but the evaporation during

page_text: the grinding would be too rapid. The employment of petroleum having a
higher boiling point would present the contrary disadvantage.
For the part which should remain in very small quantities in the color, I use
that which distils after 250° and I stop the distillation at 325°.
In order to prevent a double operation, I effect the grinding with liquid of
140° to 160° containing per litre, 55" of petroleum 2500 to 325° so that, after
drying, the powder retains from 0.1 to 0.2% of non-volatile oil.
Dated this 29th day of June 1899.
HARRIS & MILLS,
23, Southampton Buildings, London, W.C., Agents.
Improved Process of Grinding Colors Employed for Ceramic purposes.
I, EMILE LOUIS LEFRANC, of 18, Rue de Valois, Paris, in the Republic of
France, Manufacturer of Colors, Varnishes, &c., do hereby declare the nature
of this invention and in what manner the same is to be performed to be particu-
larly described and ascertained in and by the following statement:---
Colors employed for ceramic purposes are generally composed of one or several
metallic oxiles mixed with a flux capable of dissolving them and of giving to
them by roasting, the appearance of a colored enamel.
The vitreous nature of the flux and its chemical composition make the grind-
ing of these colors, an operation so much the more delicate as their extreme
fineness is one of the essential conditions of their good use.
To bring these colors to the desired degree of tenuity, they are made with
water into a paste sufficiently thin that is passed a great number of times
through flint mills or better still porcelain mills. The product is then drained
off, dried and made fairly easily into powder by the ordinary means.
However the drying having brought to the surface of the color the soluble
salts of the flux, these latter form thin crystalline crusts which in order to be
reduced to powder, necessitate another operation, generally called second
grinding.
It has been accomplished hitherto by grinding again these substances, either
with oil of turpentine or with a mixture of this latter with oil of lavender.
These liquids do not merely prevent the dissolution of the salts above men-
tioned they leave in the color, in consequence of their partial oxydation, a
variable resinous residue which will consequently facilitate the incorporation
of the powder with the fatty oil which is the vehicle preferred to dilute these
colors.
The employment of the oils of turpentine and lavender for the second grind-
ing does not present any inconvenience when the powders are to be used
immediately. On the contrary, if they kept for a longer or shorter time,
the oxydation of the resinuous product is completed and it becomes almost
insoluble in the fatty oil and consequently produces a paste which is worked
with difficulty by the brush.
To prevent these inconveniences I have sought:-
1st. For the grinding, a liquid completely volatile, upon which the air has
Do action and which moreover is not a solvent of the matters composing the flux.
2nd. To facilitate the mixing of the powder with the fatty oil, a product
soluble in this oil and upon which the air has likewise no action.
I liave found in the fractional distillation of petroleum, liquids responding
entirely to my requirements.

page_text: I employ for grinding the portions which distil between 140° to 160° C.
The choice of this temperature is not absolutely fixed; a petroleum having a
less elevated boiling point might
during the grinding would be too rapid. The employment of petroleum having
answer the purpose, but the evaporation
a higher boiling point would present the contrary disadvantage.
For the part which should remain in very small quantities in the color, I use
that which distils after 250° C. and I stop the distillation at 325° C.
In order to prevent a double operation, I effect the grinding with liquid of
1400-160° C. containing per litre, 50° of petroleum 2500-325° C., so that
after drying, the powder retains from 0.1 to 0.2 % of non-volatile oil.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. In the process of grinding colors for ceramic purposes, the employment
of petroleum upon which the air has no action.
2. In the process of grinding colors for ceramic purposes, the application or
addition of non-volatile petroleum soluble in fatty oil, non-susceptible of
oxidation under the influence of the air alone.
Dated thi. 971 T1
1000
HARRIS & MILLS,
23, Southampton Buildings, London, W.C., Agents.