The Douglas independent. [volume] (Roseburg, Or.) 187?-1885, 1884-03-22
SEvREs PORCELAIN.

The Tedious Processes OF Prepare
tfon OF the Material Used.
~. H. Haynie in San Francisco Chronicle ]
Sevres porcelain is composed of q mix
ture of feldspath, kind of rock which
is silicate of aluminium and potassium; !;
of kaolin, which is a pure silicate of
aluminium and of Bougival chalk.
When each of these three substances
has been triturated, carefully cleansed
of all foreign elements anl reduced to
an impalpable powder, they are mixed
with water in plaster -troughs, called
colues (shells), which absorb the super
fuous water, and the paste thus OBJ
tanned is called the pate, or dough, of
the porcelain. Kaolin is infusible, but
the silicate which comes from the
feldspath is fusible, and the chalk aids
it in becoming melted under the action
of extreme heat. 1t is, therefore, upon
the proportions in which they are mixed
that depends the greater or less perfec-
ton of the porcelain in it's two most
important and distinguishing features
resistance to the heat and translucency.
When the pate has been mixed there
remains the shaping of it into the re-
quired article.
At Sevres there are two processes
of doing this-turning and molding-
and not frequently the two are COM
bined in the production of porcelain.
In the first process the workman takes
ball of this dough, and after having
thoroughly kneaded it, places it upon a
potters wheel In order to give it the
desired form. In the other process
the dough is mixed with water until it
has the consistency of cream, when it
is called barbotine. This is poured
into plaster mold, on the side of
which a thin coating OF the stuff is
quickly deposited. AS it dries this
coating detaches itself by natural
shrinking process. The drying is some
times accelerated by various means,
such as the centrifugal force resulting
from rapid turning the mold on a
wheel, or compressed air acting on the
interior, or by placing the mold under
an air-pump. When the article has
been shaped the workman adds the
handle, if one be needed, and then il
passes into the hands of skillful
turner, who carefully finishes it on a
lathe.
Any ornamentations which are to be
added in relief are fixed in place and
finished by hand in colored pate on the
white articles and in white pate on the
colored ones. The colored pate is OBJ
tanned by triturating the pate-in its
natural state it is white-in little mill
with various oxides, according to the
color desired This coloring-an easy
matter for the pate tendre-is very
delicate operation for the pate dure, as
very high temperature being indis-
pensable in order to obtain the glazing,
the oxides are liable to decompose,
either fading or changing in tint, and
giving dull colors instead of the bright
shades desired. But when the color
has been fixed by the baking it is un
changeable. Sometimes there is lace
like pattern cut on the article. This
is done while the pate is soft and gen
orally by women, who acquire sucl
skill that their work has all the finenes:
of real Valenciennes.
After first baking, or the degourdi
as it is termed, the glazing is added
This is wash made out of q solution o
feldspath and quartz, and it melts and
vitriies under a high degree of heat
The real baking is with the highest
degree of heat that can be obtained ant
takes two days. 1t produces in th'
pate demi-vitrifcation, after which i
becomes porcelain.