CHINA-WARE. 



191 



The splendour and whiteness of china depend mainly on I a density of 32 oz. per ale pint. When again dried at 

 the glaze; which is stated to be formed of the whitest rock 4688 Fahrenheit, 27 



which supplies pe-tunt se, treated similarly to the others. To 

 100 pounds' weight of this white powder, is added one pound 

 of the powder of che-kao, a saline fritt, much like gypsum, 

 or alum; also 100 pounds of lime and ashes, with another 

 pound of the salt ; these are formed into fluids having like 

 specific gravity ; and then ten of the former is mixed with 

 one of the latter. With the Chinese potters, the prepara- 

 tion of the clay is constantly in operation ; and usually re- 

 mains in the pits from ten to twenty years prior to being 

 used. The longer it has remained there, the more is its 

 value ; and instances are not (infrequent, of one potter ma- 

 nufacturing his ware from clay first prepared by his grand, 

 father. 



The hoa-cfie china, a very expensive kind, which has its 

 name from its glutinous appearance, in addition to the pe- 

 tuntse, kaolin, and alumine, has steatites, (soap-stone, 

 doubtless from its saponaceous quality,) washed from its 

 impurities, oxide of iron, &c. then pulverized, abraded in 

 water, and treated similarly to the others ; and, in conse- 

 quence of this component, although its grain is very fine, 

 and its delicacy and beauty extreme, when among the com- 

 ponent parts of the glaze, presenting opportunity for 

 superior decoration by ornament, the ware is brittle, defi- 

 cient in weight, and only by great attention properly 

 baked. 



The best Persian china, of Shiraz, id equal to that of 

 Canton in every property, and superior in some particulars ; 

 it is, consequently, substituted for that frequently by the 

 Dutch merchants, and requires some judgment to be distin- 

 guished as not Indian merchandise. That its material is 

 felspar is obvious from its fracture presenting a fineness 

 of grain, and a semi-transparency similar to the Chinese ; 

 and also, because it will bear to be used as moulds for casts, 

 and as vessels in which fluids may be boiled, or minerals 

 pulverized. 



The Dresden or Saxon china has some qualities which 

 render it decidedly superior to the oriental. Its fracture 

 certainly does not exhibit a granular texture, but a com- 

 pact, shining, uniform mass, resembling white enamel, 

 proving that it is compounded of one kind of materials, 

 which by fusion will cause its density, smoothness, and su. 

 perior lustre; and another infusible, whence result its 

 beautiful white appearance, firmness, and solidity. These, 

 in combination, regularly contract together, and form china 

 more firm and compact than those of China and Japan, yet 

 equally hard to give sparks with steel, sonorous when 

 struck with wood or the hand, and not fusible by any heat 

 employed in baking. 



At Naples and Florence, beautiful china is made, ap- 

 proaching in excellence that of Japan and Canton. While 

 at Berlin, Frankendal, Vienna, and other places in Ger- 

 many, china is made of the same materials as are used 

 for the Dresden ; but, by varying either, or both propor- 

 tions, as well as processes, they differ from each other, and 

 also from that of Dresden. 



The invention of French china manufacture is due to 

 Reaumur; and establishments are formed at Paris, Ville. 

 roy, and Orleans. That of Sevres has a grain neither so 

 close nor so fine as that of Japan; but much like lump 

 sugar ; and excelling all the others of French fabrication 

 in its white shining lustre, its fine glaze, elegance of 

 shape, beautifully coloured grounds, and magnificent gild- 

 ing. Reaumur's porcelain is manufactured of pulverized 

 common glass and fluxes, or of vitrescent stones and saline 

 fluxes. 



The requisite minerals for the components of the best 

 hard China, are sparingly supplied by nature, and, there. 

 fore, secures an additional value to the ware ; while 

 those which are employed in the several kinds of earthen- 

 ware, are not uncommon in most countries. Silica and 

 alumine, whether mechanically or naturally combined, do 

 not vitrify together, although they more readily and fre- 

 quently combine than any of the other earths : it is sup- 

 posed, that, in these combinations, silica exercises the 

 properties of an acid, and alumine those of a neutralizer, 

 though not strictly an alkali. Silica, when pure, is trans- 

 parent, and, when calcined, loses much of its adhesive 

 property ; and, even in its pulverized state, communicates 

 to the ware hardness, firmness, and unalteratiou by baking. 

 Alumine is opaque, and retentive of water at extremely 

 high heats, 4717 Fahrenheit, or which fuses silver. When 

 silica and alumine are properly combined in water, their 



27 per cent, is lost. The alumine is sup- 

 plied from four kinds of clay, two from Biddeford, and 

 other two from the Isle of Purbeck, that is, pipe clay ; the 

 fracture is earthy, to the feel they are greasy, adhering to 

 the tongue; baking into a white substance, more tenacious 

 and plastic, and, though not easily fused, more fusible than 

 porcelain clay. The names of blue, brown, black, and 

 cracking, are applied according to their properties. Tbe 

 blue has more force, with a certain quantity of flint, tban 

 any of the others ; and, while contracting little, form tog-e- 

 ther a white durable ware. The brown contracts rat in r 

 more than the blue, yet supplies a very white ware whe, 

 in biscuit ; but the sulphuric acid it contains causes great 

 attention to the components of the lead glaze, else crazing 

 will ensue. The black has carbonaceous particles admix- 

 tured, which, by baking, lose their acid, and are not re. 

 garded as injurious. And the cracking produces a fine 

 white ware ; but, from its excess of alumine, so much 

 contracts by baking, that it only can be safely used in 

 combination with a certain proportion of blue clay. As 

 very accurate experiments determine that a vessel formed 

 of any of the native clays alone, will contract, from evapo- 

 ration, till sufficiently dry for baking, at least one-tenth in 

 dimension, there cannot be further reason desired, to prove 

 that plus of alumine, which readily is bibulous, prevents a 

 vessel being durable and firm. The grauen, or Cornish 

 granite, a natural mixture of quartz, mica, and felspar, is 

 used in large quantities. It is ground similarly to flint; 

 and when dried on small kilns similarly to the plaster of 

 Paris, is often called composition. The quartz prevents 

 too great contraction of the ware during baking; and the 

 felspar, having 16 per cent, of potass, renders the mixture 

 more readily vitrescent by baking, and so promotes the 

 compactness of the ware. The mica has 4 per cent, fluate 

 of lime ; and although this is but a very small quantity, 

 its potency as a flux promotes vitresceuce, and its acid 

 intimately combines with the silica, until a rise of temper- 

 ature, and the presence of water, produce a re-tendency 

 to action. This is a latent cause of crazing. The china 

 clay of Cornwall, first introduced by Mr Cookworthy, is 

 the extremely white and impalpable powder, by running 

 water washed off broken pieces of the blocks of decomposed 

 white granite, collected in catch pools, from which it is at 

 certain times taken, dried, and forwarded to the potters. 

 The washing separates the quartz and mica, and also much 

 of the potass, which causes the clay to be infusible. But 

 all the clay in this state is not alike in quality : some has 

 more potass in the felspar, and is moderately fusible at a 

 white heat ; while others remain refractory in any heat of 

 the potter's oven. In 1834, Mr Ryan introduced a native 

 clay for china, which possesses all the essential qualities 

 of the Japan kaolin. Most of the English china contains 

 the earthy residue of bones, boiled, to extract all gelatinous 

 ingredients, next calcined, and then ground ' similarly to 

 flints. This component, by increasing the porosity, aids the 

 semi-transparency, and supplies additional whiteness, by 

 the phosphoric acid correcting any iron in the other com- 

 ponents. This is the latent cause of china seldom bearing a 

 sudden rise of temperature, or sudden change. Magnesian 

 clay, in its indurated state, as soap rock or steatite, and 

 also in its plastic form, from their decomposition, has been 

 occasionally used to improve the whiteness of the body or 

 ware. It has a cream colour, strong earthy odour, mi. 

 nutely foliated texture, slight greasy lustre, takes a polish 

 from the nail, stains the fingers, is very friable, smooth, 

 unctuous, and plastic to the touch, and, on the tongue, dis- 

 solves into a pulp free from gritty particles. Only when 

 adequate aid results from alkaline components, can this be 

 used, because its pulverulent nature renders it deleterious 

 in the clay. There are also used considerable quantities 

 of slate clay and shule clay, used for different purposes 

 hereafter explained. The colour of the slate clay is from 

 ash grey to ochre yellow; it has foliated texture, is unctu- 

 ous and smooth to the touch ; scarcely gritty between the 

 teeth. The kind found in thick strata is darker coloured 

 and less plastic than that from thin strata. And that ob- 

 tained from peat mosses is rather white ash-coloured. 

 The shule clay is varied from greyish blue to bluish black, 

 with foliated texture, smooth unctuous* feel, bears to be 

 polished by the nail, small gritty particles, very tenacious 

 and ductile ; and, taken from the basseting of the coal 

 strata, to be used for saggers, and other purposes. This 

 marl, as it is called in the potteries, is the upper casing, or 



reciprocal tendencies cause strong adhesion, so that, when roofing, of the coal strata; while another kind, called 

 hardened merely by evaporation into a paste, they reaistl clunck clay, is the flooring of the strata. The brick and 

 decomposition by the atmosphere; and, when they havflLfrle clay has a colour from yellow to dark red, blue, and 

 been subjected to the heat requisite to dissipate the watery green; and, while very plastic, adhering to the tongue, 

 of the mass, in which 46 per cent, of the weight is lost, soft and greasy to the feel, and a fine earthy fracture, 



supplies a common material for coarse pottery, and as a 

 component for black, brown, and lustre wares. 



Composition of China and Earthenware. Modern che- 

 mistry has thrown much light on this subject, not only in 

 enabling us to analyze more perfectly the bodies which 

 constitute these wares, but also in determining the exact 



there remains a body durable, firm, and unaffected by 

 change of temperature. The silica requisite is obtained by 

 using the dints from the Sussex coast, and near Antrim, 

 Ireland. The best for the purpose have a blackish appear- 

 ance. They are first calcined in a small kiln, in form 

 similar to those large ones used for limestone ; next they 



are broken in pieces while hot, and cast into water in the 

 pan, in which, by mechanical power, they are abraded 

 together, till the mass has the consistence of cream, with 



proportions in which they combine; and we shall introduce 

 a series of recipes, the result of the combined researches 

 of the chemist and practical potter. The accuracy of these 



