|Antiques Digest||Browse Auctions||Appraisal||Home|
What Is China?
CHINA, or chinaware, is porcelain. It is not to be confounded with pottery. Porcelain, though first evolved from pottery, is a thing beyond and apart from it. And pottery is not porcelain.
It is quite true that porcelain is made by potters, and that a mechanical and decorative kinship exists; that its making is included within the scope of the fictile art along with the making of pottery; and that the ultimate perfection of porcelain's manufacture was developed from the processes of pottery making. But porcelain is the highest, the most precious and the most highly organised expression of the potter's art.
And it is something still more than that. Porcelain is a thing separate and distinct from pottery, because there is a fundamental difference between the body of porcelain and the bodies of all the various sorts of pottery and earthenware. This radical difference is manifest through a combination of certain well-defined physical properties which porcelain has, and which the divers kinds of pottery and earthenware have not.
Porcelain is called china, or chinaware, because China is the land of its origin and first manufacture. For centuries it was exported thence to other countries, until the secrets of its composition and manufacture were discovered. Even after that, and when the porcelain manufactories of the West were competing with Chinese products for public favour, export of the "china of China" continued in great volume and still maintains an appreciable place in Oriental commerce.
THE DISTINGUISHING PROPERTIES OF PORCELAIN. First, it is important to remember that porcelain is composed of a clay that is burnt or fired at intense heat in a furnace; it is not a glass or vitreous substance that has been molten. There are two fundamental things to be considered in studying porcelain: (1) the body of which it consists or the paste, as it is called and, (2) the glaze, that is to say,the transparent vitreous or glassy substance with which the body or paste of the object, platter, cup, vase or whatever it may be, is coated. When the paste or body is left unglazed, as is often the case with medallions, busts or small groups of sculpture, it is spoken of as biscuit. The term biscuit is also used to designate in general the pieces of porcelain, of whatever type, before they have been glazed. In the making of Chinese porcelain, there is, as a general rule, no "biscuit" stage; the fluid glaze is applied directly to the air-dried clay vessel and glaze and body are fired at one and the same operation.
The two essentially distinctive qualities possessed by porcelain, the qualities that differentiate it from other products of the potter's art, are (1) the whiteness of its body, not merely on the surface but clean through the substance, as it appears when broken; and (2) its greater or less degree of translucency where the body is at all thin. The edges of thin plates or saucers, thin lips, and mouldings, when held against the light, should be translucent. Bowls, cups, and not seldom the whole body of plates and saucers should be translucent, when subjected to this test against the light, unless the body is of unusual thickness. Oftentimes, too, when the edge of a bowl or plate is struck it will give forth a clear, bell-like note.
In addition to the whiteness and translucence of porcelain, there is a peculiarly distinctive manner in which its glaze reflects the light, while to the touch the surface is smooth and soft as nacreous shell lining.
THE DIFFERENT SORTS OF PORCELAIN Porcelain is classified as hard paste porcelain and soft paste porcelain. There is also a third porcelain composition known as bone porcelain, which occupies a more or less middle ground between the hard paste and soft paste types. It is the fashion in some quarters to refer to hard paste porcelain as true porcelain while soft paste porcelain and bone porcelain are termed artificial porcelains. However, all three have so much in common, and all three are so widely separated in every respect from other fictile bodies, that it seems much wiser, on the whole, much fairer, and much less provocative of confusion and misunderstandings to adopt the former classification of hard paste, soft paste and bone porcelain.
HARD PASTE PORCELAIN Hard paste porcelain is distinguished by its hardness, its high resistance to heat, its resistance to acids and its impermeability to staining fluids, its close, compact texture, its complete vitrification, its translucence, the nature of its fracture when chipped or broken which is conchoidal or shell-like, very much like the fracture of a piece of flint, and its clear, bell-like note when sharply struck. When we speak of complete vitrification it means that the several elements in the composition of the porcelain body are so thoroughly blended and compacted by the intense heat of the firing that the substance appears dense and absolutely homogeneous and is hard and smooth to the touch. This quality is readily apparent in the "biscuit," at the points of fracture where glazed porcelain is chipped or broken, and on the bottom edges of foot-rims that are free from glaze. Complete vitrification also implies that, since the glaze, in the intense heat of the firing, has become virtually part and parcel of the body which it covers, it cannot be chipped off and separated from that body in flakes.
The materials of which hard paste porcelain is made are, first, kaolin or china-clay, a white earthy substance which is a product of decomposition of the felspar con tained in granitic rocks; and, second, petuntse or chinastone, which contains felspar, the silicate of alumina and potash, or sometimes soda. The felspar is closely allied with granite, or kindred rock, in a somewhat weathered condition and is frequently associated with more or less quartz and mica. The china-clay or kaolin is not fusible, even at the highest temperatures to which the kiln can be brought; the petuntse, china-stone or felspar is fusible at an high temperature. William Burton, one of the greatest living authorities on porcelain and porcelain technique, notes that "at the high temperature to which the porcelain is exposed during the firing a gradual chemical interchange takes place between the various silicates composing the mixture. The fusible silicates, such as the felspar and mica, begin to melt and attack the free silica and the kaolin, and when the changes are complete we get a dense, hard, white porcelain, quite translucent if sufficiently thin. . . . However intensely fired the body may be, it never becomes transparent or clear like a piece of glass,for the glassy silicates that result from the fusion are penetrated through and through with opaque needles or rod-like crystallites." The deflections and diffusion of the rays of light through this vitreous fused body produce the soft translucence so highly prized in fine porcelain. In other words, the melting of the fusible china-stone in the kiln to a glassy substance that holds the non-fusible china-clay or kaolin in suspension produces the marked translucent and vitreous character of hard paste porcelain. The china-clay or kaolin has been aptly likened to the bones of the porcelain body, while the fusible china-stone is the flesh. To carry the simile one step further, the glaze may be likened to the skin.
All hard paste porcelain has not a body or paste of identically the same composition. The character depends upon the proportions of china-clay or kaolin, on the one hand, and of petuntse or felspar, on the other, that enter into the mixture before it is shaped and fired. The larger the amount of kaolin, the harder and more infusible the finished porcelain. The great plasticity of the clay mixture when it contains an high percentage of kaolin renders the utmost care necessary to avoid mishaps before drying and firing. As much as 65%. of kaolin can be used in the mixture. When there is an high percentage of kaolin, the resulting porcelain is said to be of "severe" type; when the percentage is much lower the porcelain is said to be "mild." To the "severe" type belongs much of the earlier hard paste porcelain of Sevres and most of the German porcelain. China of this type may possess admirable utilitarian qualities, but as a substance it is apt to be harsh to the sight and cold and hard to the touch. The china of China belongs to the "mild" type, and so does much of the porcelain made at Sevres in recent years. Irrespective of decoration, the mild porcelain is much more delightful to see and more sympathetic to the touch. In every way it is far more mellow and satisfactory. The reader can have no better object lesson in this respect than by comparing a piece of German porcelain with a piece of Chinese; the latter is mellow, lovable and seductive, the former is brutally hard and unsympathetic. Incidentally, the severe porcelain does not lend itself nearly so kindly to decoration as does the milder type.
SOFT PASTE PORCELAIN Soft paste porcelain is sometimes called artificial porcelain because some of the materials entering into its composition were substitutes for the materials used in the making of Oriental porcelain which, from the very outset, was the acknowledged model for imitation. These substitutes were arrived at as a result of conjectures regarding the nature of Oriental china and experiments on the part of European porcelain pioneers to approximate the qualities displayed by Oriental models.
Soft paste porcelain is distinguished from hard paste porcelain by the softer whiteness of its body, sometimes distinctly creamy in tone, and by its usually greater translucence, though whiteness and translucence are qualities common to all porcelain. It is also distinguished by the nature of its fracture, when chipped or broken; the unglazed portion of the body thus exposed is granular and chalky. The break or chip, too, is apt to be straight and not conchoidal or flint-like as in the case of hard paste porcelain. The substance, furthermore, is much softer and yields readily to filing. Sometimes the translucence of soft paste porcelain is slightly tinged with yellow. Soft paste porcelain has not as great resistance to heat as that possessed by hard paste china.
The materials entering into the composition of soft paste china are, first, a white-firing clay, and, second, a fusible silicate such as a frit of glass, sand or broken and pulverised china. When deposits of kaolin were discovered in Europe, the kaolin was made use of. Most of the early European china was soft paste porcelain and, in nearly all cases it possesses a rarely mellow quality that much of the hard paste china totally lacks. The loveliest and most highly prized old Sevres china was all of soft paste.
In the process of firing in the kiln the artificial silicates melt, envelope and partly dissolve the clay so that, as Burton points out, "again a material is obtained in which a clear transparent base holds in suspension white and opaque particles, and such substances consequently exhibit something of the soft translucence that distinguishes the porcelains as a class."
BONE PORCELAIN Bone porcelain, as noted before, may be said to hold a middle ground between hard paste and soft paste porcelain, representing, so to speak, a compromise between them. The materials of which the body or paste consists are mainly kaolin, felspar, petuntse or china-stonewhichever name you choose to apply to it-and, thirdly, a quantity of bone-ash. This composition was discovered and the process developed in England from about 1750 onward. As Burton aptly points out, "we may regard English bone-porcelain, so far as the body of the ware is concerned, as a true porcelain paste which has been rendered more fusible by the addition of a large proportion of calcium phosphate in the form of bone-ash."
In its distinguishing qualities bone porcelain likewise occupies an intermediate position between the hard paste or natural felspathic porcelains, on the one hand, and the soft paste or artificial glassy porcelains, on the other. It is not generally so white as the hard paste, but more white than the soft paste. Also, it is not quite so hard, nor so impermeable to the action of acid or staining fluids, as the hard paste body, but it is harder and less permeable than the soft paste. Although it holds comparatively a middle ground between the two, yet in its qualities it somewhat more closely resembles the hard paste. In its fracture it is more akin to the hard than to the soft paste. It has the durability of the hard paste and the softer quality of the soft paste glaze.