Rensselaer Republican, Volume 18, Number 18, Rensselaer, Jasper County, 7 January 1886 — How Porcelain Ware is Made. [ARTICLE]

How Porcelain Ware is Made.

To earthenware the blue clay gives toughness and solidity; flint gives whiteness, kaolin whiteness and porousness, and Cornish stone aot’s as a sort of flux, binding all together. These materials, being weighed and measured, are placed, together with a large quantity of water, in huge vats fitted with an agitator called a “blunger,” by means of which they are thoroughly stirred up and mixed together. As my oonrteous guide raises the lid of one of these "blunging” machines, 1 descry, as it were, the interior of a vast churn, filled with a .strong, white sea, as if the cliffs had got with the tide in the manner depicted by some painters of seascapes. This beautifully white fluid runs off, when its parts are judged to be sufficiently mixed, into troughs, and is strained through sieves of lawn, varying in fineness from twenty-two to thirty-two threads to the inch. It is being tested by weight, a certain measure being required to weigh a certain number of ounces. The slip now reposes for a while in quaint receptacles shaped like the Noah’s ark given to children. To get rid of the superfluous dampness of the compound “slip,” it is forced by means of pumps into bags of strong cloth. It is then pressed and sometimes cut up and pressed again, being then ready for the thrower. When the sort of sausage machine just described has done its work, and the slip has been pressed, the material is of the cousistancy of stiff dough. In this condition it comes into the hands of the potter, but not directly. Before it reaches him it is weighed out int© lumps and handed to him by the girl who acts as his assistant. When the lump of clay is finally handed to the potter he deals with it in a wonderful manner. Placed on the horizontal wheel revolving befoire him, the clay is made to perform the most extraordinary evolution. It spreads out, leaving a hollow center, and grows like a mush-room under his skillful hand. , It becomes anything he likes. It may be a bowl, a cup, or assume any other shape. As the clay revolves rapidly the workman has only to change the position of his hand to produce any shape he may wish. In the so-called "green bouse” © large quantity of ware is drying preparatory to being “fired.” This process is the crucial test of pottery. All the preceding operations have been conducted with a distinct view to this one. All the combinaiions of clay, flint, stone, or bone have been made with forethought of the kiln in which the ware will be partially vitrified. Earthenware and porcelain are only, as is well known, less perfect forms of glass, or rather, of glass in another stage of development. When the earthenware slip cups and saucers, mugs and jugs, are sufficiently dried, they are ready for the “biscuit” kilns, as they are oddly called, for the ware is not twice baked in them, nor is it good to eat Some kinds of ware are submitted to the intense heat of the kiln three times, all twice—once in biscuit, once in glaze. When painting is introduced over the glaze, as in the ole Sevres pate temlre and the various kinds of fine porcelain, there is a third tiring. Before being placed in the kiln 3 all the articles thrown, turned, or molded are arranged in the “saggers,” receptacles of coarse clay, very thick and strong, like deep pie dishes. Into these the various art cles are packed with considerable skill, little triangles being placed between each to prevent their touching each other, and the saggers are next packed together in the or oven, each saggar being lined'at the bottom with a liiyer-of rock sand.—Piled ono on the other, tho saggers make a fairly compact column, and when the oven, some nineteen feet in altitude, is filled, the fire is applied. It will be understool that the fire by no means touches either the ware or the saggars in which it is enclosed. They are simply in an oven about to be raised to a tremendous heat. The firing is dono by means of flues so arranged as to diffuse intense heat throughout the whole intcror of the ovens. The firing is a ticklish operation, requiring the supervision of a skilled workman capable of existing without sleep for some thirtysix or forty hours. At first tho heat is applied gently, for fear of cracking the ware, and the fireman has an anxious time of it. Little openings in the brickwork enable him to judge of the progress of his work. The heat of a biscuit oven during the last twentyfour hours is intense, between 20,000 and 30,000 degrees F. As the ware has taken from forty to fifty hours in firing, so does it require an equal time to become cool. —English Magazine.