CHAPTER X

CRYSTALLINE GLAZES

FlambÉ or transmutation glazes of the Chinese potters—The Royal Copenhagen Factory produces the first specimen of crystallized glaze in 1886—Blue crackled glaze produced with design under control.

During the last decade of the nineteenth century the Western potter came under the spell of the modern chemist. Scientific study applied to the body and glaze and vitrifaction of the materials composing porcelain and faience, together with a closer study of the exact conditions of temperatures in the kilns, resulted in the discovery of certain well-defined decorative qualities in connection with glazes which, after considerable experiment, offered practically a new field for colour-work of a very beautiful nature.

In the flambÉ or transmutation glazes for which the Chinese potters were renowned, the effects of variegated or splashed colour are due to the capricious action of the fire on the glazes during the firing process. The single-coloured glazes of the Chinese applied to vases and other objects have been much prized by Europeans. The tints are very numerous, sea-green or celadon, yellow, red, blue, purple, brown, black, and other tones. These include the celebrated sang-de-boeuf colour of French collectors, so highly prized in China. It is thought probable that many of these single-colour glazes have been applied at a somewhat lower temperature, termed by the French demi-grand feu.

The mottled classes owe their appearance less to the difference in the colouring matter than to the manner in which it is applied. They are termed in French flambÉ, and there is no doubt that they were originally accidentally produced. According to the letters of a Jesuit missionary, PÈre d'Entrecolles, written in the early years of the eighteenth century, such vases were called Yao pien or transmutation vases. Such types, with turquoise colour passing into green, green melting into purple, and amber fading into grey, are suggestive of the permutation of colour harmonies which these transmutation glazes undergo in the furnace.

Beside the flambÉ glazes there are crackled glazes of turquoise-blue, apple-green, or of greyish white. This crackle porcelain is now artificially produced, but it doubtless owes its origin to accident and caprice of firing.

In flambÉ glazes an English potter, Mr. Bernard Moore, of Longton, has succeeded in producing sang-de-boeuf colour with delightful gradations of tone; unhappily, some of these pieces were destroyed by fire at the Brussels Exhibition in 1910.

Copenhagen produces the First Crystalline Glaze.—At the Copenhagen factory grand-feu coloured glazes have been developed in a remarkable manner. The crystal glaze, the serpent-skin, the tiger-eye, and crackled glaze, as well as many other varieties, show effects which hitherto have been unknown in porcelain, and have won the admiration of all connoisseurs. The inception of the crystalline glaze was due to Hr. Clement, the chemist at the Royal Copenhagen Factory, and it was owing to the indefatigable energy and experiments of Hr. Clement that, in 1886, the first piece of porcelain with crystalline glaze achieved a record for the Copenhagen laboratory and studio. Since that day other European potters have succeeded in producing crystalline glazed ware of exceptional beauty.

We illustrate a fine specimen of the early crystalline glaze of Copenhagen now preserved at the Museum of the National Porcelain Manufactory at SÈvres. It represents a frog on a leaf. "We should like specially to point out," says M. Edouard Garnier, the Director of the Museum at SÈvres, writing in 1894, "a large water-lily leaf on which a frog is imbedded in a thin layer of ice, which it has just succeeded in breaking. We have never seen a more striking example of what may be attained by a purely scientific process applied to art decoration, and we cannot repress the wish that this example may be followed by our modern ceramists." This is one of Arnold Krog's fine conceptions.

This specimen of the work of the Copenhagen chemist, Hr. V. Engelhardt, in crystallized glaze, has been followed by many notable achievements on his part. In 1902 there was a figure of a Polar Bear lapping water, modelled by Arnold Krog and produced in crystalline glaze by Hr. Engelhardt. This, of which only thirty pieces were made, was executed for an artistic club in Paris. Another fine subject is that representing two Polar Bears on the ice, one mounted on a frozen pinnacle. The whole is a skilful piece of modelling by C. E. Bonnesen, and crystalline glazing by Hr. V. Engelhardt.

New shapes are continually being invented, and a long chain of experiments in the laboratory has resulted in the production of some very remarkable examples of colouring which are always welcome to collectors, who are quick to realize that no two examples can ever be the same. All colours can be handled in this manner. The range is a wide one, and the surprising gradations of tone have a charm undoubtedly their own, and not unworthy to be regarded as representative of some of the most wonderful creations of the modern potter. The metallic oxides in the hands of the twentieth-century chemist become possessed of magical properties and are transformed into tender harmonies vibrating with exquisite tones. Yellows, and blues, and browns merge into mauve or grey, in delightful tenderness, and black and white are included in the colour schemes of which this style is now capable.

Blue Crackled Glaze.—In regard to crackled glazes there is evidence that they are coming more under the governance of the chemist. There is a beautiful deep blue variety produced at Copenhagen, with a network of crackle graduated to a nicety, now swelling, when on the belly of the beaker or vase, and now contracting into minute meshes when on the slender neck. This is completely under mechanical control. As yet blue is the only colour produced in this style.

At the Brussels Exhibition, 1910, the SÈvres factory exhibited some large vases with crystalline glaze evidently under the complete mastery of the potter and chemist. These vases were of a very fine character, and the suggestion arises that at no far distant date the glazes now termed "transmutation" or adventitious will be completely mastered by the latest developments of modern science as applied to pottery, and thus "transmutation" will be a word of the past.

The technique of Copenhagen differs from that of SÈvres or of Berlin. In these latter cases the crystals appear like spots on the surface, whereas in Copenhagen ware the crystals have a more subtle and intimate incorporation with the glaze. They never stand on the surface, and often, as in the mellow brown glaze, they lie beneath and glow in reflected light.

A series of effects in broken colour, delicate in marking and veined and mottled in most pleasing character, is being attempted in vases. We illustrate several types in whole and partial crystallization, which lose considerably by appearing as black-and-white illustrations. Such vases are conspicuous for their revelry in colour, not the hard, dense, opaque colours of the old Chinese single glazes, but the limpid, vibrating, restless subtleties of Nature's own play of pulsating colours in changeful mood—the dazzling and fairy-like opalescence of the frost and the deep blue of the ice cave, or the pale amber sand-dunes imperceptibly fading into a translucent green stretch of waters, with the vaporous haze of a violet sky. In the white heat of the modern furnace the flowers of a prehistoric day, which have lain buried in the coal seams of an alien land, transmute the dull clay and the mineral glaze under the hand of the modern magician into colour nocturnes.