Porcelain. Dillon Edward
of the East than any other European ware. Finally, M. Vogt points out that most of the other European porcelains, those made in the Limoges district, in Germany and in Denmark, are of an intermediate type, and that they allow the use of either a felspathic or of a calcareous glaze (Vogt, La Porcelaine, pp. 144 seq.).9
To return to our raw materials, which we may now suppose to be weighed out in a dry state in the required proportions. These are once more thoroughly mixed with water to form the slip or barbotine, which is again passed through a fine sieve. To remove any particles of iron which may have come from the machinery or elsewhere, and which if allowed to remain would form unsightly stains on the finished ware, it is usual to pass the slip at this stage through a vessel in which a number of horse-shoe magnets are suspended. In some of the large French factories a more complicated machine is used for this purpose. The superfluous water has now to be removed either by evaporation or by pressure between canvas bags in the manner described above. The paste may then be passed through a pug-mill to render it uniform in consistency.
A curious question arises with regard to the prepared clay. There was formerly a widespread idea, which may contain an element of truth, that instead of handing the clay at once to the potter, it should be kept, under certain conditions, for a long space of time that it may undergo a process of ‘aging’ and fermentation. By the ‘aging,’ the working qualities, especially of a ‘short’ or non-plastic paste (such as that in use at Sèvres in the eighteenth century, in making the pâte tendre), were doubtless increased, the more so when the clay was at intervals subjected to fresh kneading and watering. With regard to the long periods for which the clay was kept by the Chinese, the most exaggerated statements were formerly made. Mr. William Burton is of opinion that there may be in some cases an evolution of carbonic acid and sulphuretted hydrogen when natural plastic clays are used, for these may contain both vegetable remains and small quantities of iron pyrites. But the change, he thinks, is chiefly a physical one, due to the settling down of the mass. Might there not also, I would suggest, be a change of a more intimate nature, due to the formation of gelatinous silica and perhaps also of fresh alkaline or other silicates, among these minutely comminuted particles of various materials now freshly brought together? We know very little of the conditions that give to natural clays their peculiar unctuous quality and their plasticity.
We come now to what has been called the ‘shaping’ of the clay, using that word as an equivalent to the French façonnage to include all the processes, throwing on the wheel, turning of the lathe, ‘pressing’ and ‘casting,’ by which the desired form is given to the vessel.
The Potter’s Wheel, perhaps the most ancient of all mechanical contrivances, is still largely used in the shaping of porcelain, and that, too, in a simple form which differs little from that employed three or four thousand years ago in Egypt,10 and perhaps for nearly as long a period in China. From an æsthetic standpoint, the wheel holds the same relation to the art of the potter as the brush does to that of the painter. It is perhaps a just cause of reproach against that branch of the ceramic art with which we are now concerned, that so comparatively little use is made of the potter’s wheel. Not only in Europe, but for long ages in China also, the use of the wheel, for many classes of vessels, has been replaced by various processes of moulding. With us, but not in the East, a third process, that of ‘casting’ with liquid slip, is largely used. But when made either by casting or moulding, the hand of the potter is not seen in the shape of the finished vessel. By means of the wheel alone do we get the full expression of the peculiar qualities of a plastic material. This was recognised by the Greeks, when the potter who made the vase signed his name by the side of the painter who decorated it. This it is that gives a certain charm to the roughest earthenware which we may look for in vain in the most elaborately decorated specimen of either Chinese or European porcelain.
The clay as it comes from the filter-presses or from the drying-beds is subjected to a series of kneading processes to ensure uniformity of texture. The last of these is the ‘slapping,’ when the clay is made up into hollow balls, and thrown vigorously on to a board until all bubbles and irregularities of texture are removed.
The thrower’s wheel is essentially a revolving vertical spindle, with a small round table at the top, beside which the thrower sits. The clay is handed to him in balls, and he throws it upon the whirling table between his knees. The table is put into motion either directly by the pressure of the workman’s foot on a lower table, or by some arrangement of straps and pedals. If the movement is given by the potter himself, as is still the case at Sèvres, and to some extent in China, there is the advantage that a more delicate and intimate control of the speed is possible. The movement of the clay under the potter’s hand is instinctively regulated by him. Every one has seen and marvelled at the wonderful process. The clay is first drawn up into a pillar, and then depressed into a flat cake, so that the circular arrangement of the particles may spread through the whole mass. The thrower then opens the hollow of the vessel with his thumbs, and proceeds to give it the desired shape, moistening his hands at intervals by dipping them into the slip. Small pieces are shaped between the thumb and first finger, either of one or of both hands. For larger pieces the whole hand and wrist is called into play, with the assistance, it may be, of a sponge. Still larger vessels are built up by piling on to the circular edge as it revolves strips of the clay. Delicacy of hand is of the greatest importance—the pressure applied and the movements of the fingers must be regulated by the nature of the clay, and especially by its greater or lesser plasticity. It is essential that the workman should not only press evenly and steadily on the clay as it rises, but that the speed of the rotation should have a definite relation to the rate at which he raises his hands. With a ‘fat’ or unctuous clay especially any irregularity of pressure will betray itself, and the marks will be more prominent after firing. This is the origin of the spiral ridges that we often see on the surface not only of common earthenware, but sometimes of high-class porcelain. To this cause are due the rings so characteristic of Plymouth porcelain; this ‘wreathing’ or ‘vissage’ is sometimes seen on Chinese porcelain also.
When the thrower has finished his vessel, it is cut off from the table by a piece of thread or by a brass wire, and taken to the stoveroom to dry and harden. When sufficiently dry the vessel is placed on a lathe, and the turner shaves off all superfluous clay. The finer mouldings (using the word here in its architectural sense) may also be given at this stage, and sometimes the surface is shaped by a ‘profile’ of steel (it may be a piece from the blade of an old saw), which cuts the surface down to the desired shape. The shavings are carefully preserved and returned to the slip-house, to be blended with the new clay, the working qualities of which are thereby improved.
There are certain parts, especially handles, spouts, and projecting ornaments, which must in all cases be separately moulded. The foot also, in the case of large vases, is separately prepared and subsequently attached. These parts are made in plaster moulds by the ‘handler,’ whose duty it now is to fix them to the vase. Carefully marking the exact place, he spreads on it a thin layer of slip with a spatula, and then presses home the handle or other appendage. Should, however, the two surfaces be dry and absorbent, it may be necessary to add some gum to the slip thus employed. A similar process, but one requiring greater care and skill, is that of fixing together the separate pieces of large vases and figures. This is done in the way we have already described in the case of the handles and spouts—that is by applying a coating of slip to the parts to be joined.
It is at this stage that any decorations in relief that may be required are applied to the surface. These are often made in flat moulds, and to fix them it is enough to run a little water from a camel’s hair pencil behind the ornament after adjusting it to its proper place. These processes of fitting on of appendages and ornaments are included by the French under the term garniture.
Moulding and Pressing.—It is evident that only vessels of a cylindrical or conical form, or, more exactly, such as have a circular section when divided horizontally, can be formed on the wheel. To produce any other form, the vessel must be either shaped directly by the hand or made in some kind of mould. The use of moulds for pottery is as old, if not older than that of the wheel. It was in this way that the Ushabti figures of the old Egyptians were made, and many of these date back to the Early Empire. So in China,
I should, however, be inclined to class not only much of the porcelain of Japan, but some of that made in Germany and in south-west France, rather in the ‘severe’ kaolinic than in the intermediary class of M. Vogt.
We can, however, distinguish, in the tomb paintings of the Middle Empire, an earlier form without the lower table. This earlier type, moved by hand from the upper table, was that used by the Greeks at least as late as the sixth century B.C., and a similar primitive wheel is still used in India. On later Egyptian monuments of Ptolemaic time, the potter is seen moving the wheel by pressing his foot on a second lower table, as now at Sèvres and elsewhere. Both forms of wheel appear to have been used by the Italian potters of the Renaissance.