Part 100

GROUND CERAMICS—LAYING OIL FOR: See Oil.

«Notes for Potters, Glass-, and Brick-makers.»—It is of the highest importance in selecting oxides, minerals, etc., for manufacturing different articles, for potters’ use, to secure pure goods, especially in the purchase of the following: Lead, manganese, oxide of zinc, borax, whiting, oxide of iron, and oxide of cobalt. The different ingredients comprising any given color or glaze should be thoroughly mixed before being calcined, otherwise the mass will be of a streaky or variegated kind. Calcination requires care, especially in the manufacture of enamel colors. Over-firing, particularly of colors or enamels composed in part of lead, borax, antimony, or litharge, causes a dullness of shade, or film, that reduces their value for decorative purposes, where clearness and brilliancy are of the first importance.

To arrest the unsightly defect of “crazing,” the following have been the most successful methods employed, in the order given:

I.—Flux made of 10 parts tincal; 4 parts oxide of zinc; 1 part soda.

II.—A calcination of 5 parts oxide of zinc; 1 part pearl ash.

III.—Addition of raw oxide of zinc, 6 pounds to each hundredweight of glaze.

To glazed brick and tile makers, whose chief difficulty appears to be the production of a slip to suit the contraction of their clay, and adhere strongly to either a clay or a burnt brick or tile, the following method may be recommended:

Mix together:

Ball clay 10 parts Cornwall stone 10 parts China clay 7 parts Flint 6 1⁠/⁠2 parts

To be mixed and lawned one week before use.

«To Cut Pottery.»—Pottery or any soft or even hard stone substance can be cut without chipping by a disk of soft iron, the edge of which has been charged with emery, diamond, or other grinding powder, that can be obtained at any tool agency. The cutting has to be done with a liberal supply of water fed continually to the revolving disk and the substance to be cut.

«BRICK AND TILEMAKERS’ GLAZED BRICKS:»

«White.»—When the brick or tile leaves the press, with a very soft brush cover the part to be glazed with No. 1 Slip; afterwards dip the face in the same mixture.

«No. 1 Slip.»—

Same clay as brick 9 parts Flint 1 part Ball clay 5 parts China 4 parts

Allow the brick to remain slowly drying for 8 to 10 hours, then when moist dip in the white body.

«White Body.»—

China clay 24 parts Ball clay 8 parts Feldspar 8 parts Flint 4 parts

The brick should now be dried slowly but thoroughly, and when perfectly dry dip the face in clean cold water, and immediately afterwards in glaze.

«Hard Glaze.»—

Feldspar 18 parts Cornwall stone 3 1⁠/⁠2 parts Whiting 1 1⁠/⁠2 parts Oxide of zinc 1 1⁠/⁠2 parts Plaster of Paris 3⁠/⁠4 part

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«Soft Glaze.»—

White lead 13 parts Feldspar 20 parts Oxide of zinc 3 parts Plaster of Paris 1 part Flint glass 13 parts Cornwall stone 3 1⁠/⁠2 parts Paris white 1 1⁠/⁠4 parts

Where clay is used that will stand a very high fire, the white lead and glass may be left out. A wire brush should now be used to remove all superfluous glaze, etc., from the sides and ends of the brick, which is then ready for the kiln. In placing, set the bricks face to face, about an inch space being left between the two glazed faces. All the mixtures, after being mixed with water to the consistency of cream, must be passed 2 or 3 times through a very fine lawn. The kiln must not be opened till perfectly cold.

«Process for Colored Glazes.»—Use color, 1 part, to white body, 7 parts. Use color, 1 part, to glaze, 9 parts.

«Preparation of Colors.»—The specified ingredients should all be obtained finely ground, and after being mixed in the proportions given should, in a saggar or some clay vessel, be fired in the brick kiln and afterwards ground for use. In firing the ingredients the highest heat attainable is necessary.

«Turquoise.»—