(_Concluded from page 326._)
_Wedgewood's Staffordshire Ware._
[11] By Mr. A. Aikiu, in Trans. Soc. Arts.
Lastly is the manufacture of those species of glazed pottery known by
the general name of Staffordshire ware. The date of this ware is about
sixty years ago, and it unquestionably originated with the late Mr.
Wedgewood. It not only originated with him, but was carried by his
knowledge, his skill, and his perseverance, to a degree of excellence
which, in several points, has never been surpassed, and in some has
never been equalled.
He perceived that the defects of the delft ware, at that time the only
species of pottery employed for common domestic purposes, were the
softness and looseness of texture of its body, which obliged the potter
to make it thick and clumsy and heavy, in order to ensure to it a
moderate durability; and that its porousness, as well as its dirty grey
colour, required a thick coating of white enamel, which added still
farther to its bulk and weight, and which, consisting for the most part
of lead and arsenic, was hardly safe for culinary use.
He began, therefore, by inventing a body for earthenware, which at the
same time should be white, and capable of enduring a very high degree of
heat without fusion, well knowing that the hardness of the ware depended
on the high firing to which it has been subjected. For this purpose,
rejecting the common clays of his neighbourhood, he sent as far as
Dorsetshire and Devonshire for the whiter and purer pipe-clays of those
counties. For the siliceous ingredient of his composition he made choice
of chalk-flints, calcined and ground to powder.
It might be supposed that white sand would have answered his purpose
equally well, and have been cheaper; but, being determined to give the
body of his ware as great a degree of compactness as possible, it was
necessary that the materials should be reduced to the state almost of an
impalpable powder; and calcined flints are much more easily brought to
this state by grinding than sand would be. The perfect and equable
mixture of these two ingredients being a point of great importance, he
did not choose to trust to the ordinary mode of treading them together
when moist, but having ground them between stones separately with water
to the consistence of cream, he mixed them together in this state by
measure, and then, evaporating the superfluous water by boiling in large
cisterns, he obtained a composition of the most perfect uniformity in
every part. By the combination of these ingredients, in different
proportions, and exposed to different degrees of heat, he obtained all
the variety of texture required, from the bibulous ware employed for
glazed articles, such as common plates and dishes, to the compact ware
not requiring glazing, of which he made mortars and other similar
articles. The almost infusible nature of the body allowed him also to
employ a thinner and less fusible glaze, that is, one in which no more
lead entered than in common flint glass, and therefore incapable of
being affected by any articles of food contained or prepared in such
vessels. With these materials, either in their natural white or
variously coloured--black by manganese, blue by cobalt, brown and buff
by iron--he produced imitations of the Etruscan vases, and of various
other works of ancient art, such as the world had never before
seen--such as no subsequent artist has ever attempted to rival. His
copies of the Portland vase are miracles of skill; and the other
specimens of similar works may give some idea of the many beautiful
works that were produced in his manufactory. In table ware, for many
years he led the way almost without a rival; but the immense demand
occasioned by the successive improvements of this article, which first
put down the use of delft, and then of pewter, gave ample room and
encouragement to men of capital and skill to enter the field of profit
and competition. Much good has hence resulted; many subordinate
improvements have been effected and are almost daily making; and a new
variety of ware, called ironstone, has been invented, and so rapidly and
judiciously improved, that, in appearance and in many of its intrinsic
properties, it bears a close resemblance to the older and coarser
porcelains of China itself.
I shall conclude by a summary account of the manufacture of the best
table ware; for a considerable part of which I am indebted to notes
taken by Captain Bagnold, when visiting a pottery, inferior, perhaps, to
none in the country.
The materials of the Staffordshire ware are calcined flints and clay.
The flints are burnt in kilns, and then, while hot, quenched in water,
by which they are cracked through their whole substance. After being
quenched they are ground in mills with water. The mill is a hollow
cylinder of wood bound with hoops, and having a bottom of blocks of
chert, a hard, tough, siliceous stone: the mill-shaft is perpendicular,
and has two horizontal arms passing through it cross-wise. Between these
arms are laid loose blocks of chert, which are moved round on the
bed-stone as the arms revolve, and thus grind the flint with water to
the consistence of cream.
The clay, from Dorsetshire and Devonshire, is mixed with water, and in
this state is passed through fine sieves to separate the grosser
particles. The flint and clay are now mixed by measure, and the mud or
cream is passed through a sieve in order to render the mixture more
complete.
In this state it is called slip, and is now evaporated to a proper
consistence in long brick troughs. It is then tempered in the pug-mill,
which is an iron cylinder placed perpendicularly, in which an arbor or
shaft revolves, having several knives projecting from it, the edges of
which are somewhat depressed. By the revolution of these the clay is cut
or kneaded, and finally is forced by their action through a hole in the
bottom of the cylinder, and is now ready for use. Cups, pots, basins,
and other round articles, are turned rough on the horizontal potter's
wheel; and, when half dried, are again turned in a lathe. They are then
fully dried in a stove, and the remaining roughnesses are afterwards
removed by friction with coarse paper. Articles that are not round, and
the round ones that have embossed designs on their surface, are made of
thin sheets of clay rolled out like dough, and then pressed into moulds
of plaster of Paris; the moulds being previously dried, absorb the
superficial moisture of the clay, and thus allow it to part from them
without injury. The two or three separate pieces composing the article
are then united by means of fluid slip. Spouts and handles of jugs and
tea-pots are made and united with the body of the vessel in the same
way. Small handles, beadings, mouldings, &c. are formed by means of an
iron cylinder, having its bottom perforated so as to mould the clay, as
it passes through, into the required figure. A piston is inserted into
the top of the cylinder, and caused to descend slowly by means of a
screw, in consequence of which the clay is continually passing out
through the perforation, and is cut off in lengths.
Plates are beaten or rolled out of a lump of clay, and are then laid on
a mould turned to the shape of the upper surface of the plate. A
rotatory motion is given to the mould, and an earthenware tool
representing a section of the plate is pressed upon it; thus the plate
is made smooth, has a uniform thickness given to it, and it takes a
perfect cast of the mould. Cups, saucers, and basins, when rough-turned,
are dried on the block to prevent them from warping.
The ware being thoroughly dried, is packed into saggars and burnt in the
furnace to biscuit. Patterns for flat, or nearly flat surfaces, are put
on by printing the pattern from a copper-plate with an ink composed of
oxide of cobalt, oxide of iron, or other colouring matter, mixed with
oil. The impression is taken on soft paper, and is applied to the
surface of the biscuit, and slightly rubbed to make the print adhere:
the biscuit is then soaked in water till the paper may be stripped off,
leaving the print or pattern behind[12]. The ware is then dipped in the
glaze, which is a mixture of flint slip and white lead, and the bibulous
quality of the biscuit causes a sufficient quantity to adhere: the piece
is then dried and again passed into the furnace, which brings out the
colours of the pattern, and at the same time vitrifies the glaze.
[12] This very ingenious method of tranferring printed patterns
to biscuit ware was invented at the Porcelain works at
Worcester.
The finest patterns are applied after the glazing has been completed, by
taking the impressions from the copperplate on a flexible strap covered
with a strong gelatinous mixture of glue and treacle. This strap is then
pressed on the ware, and gives the impression in glue, the colouring
powder is then dusted over it, and a sufficient portion adheres to the
damp parts to give the pattern, after having been again in the furnace.
The more elaborate patterns on earthenware, and all those on porcelain,
are finished by penciling in.
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