"ENCAUSTIC (FIGURED) TILES, having a flat surface with the ornament inlaid, or slipped in various colored liquid clays. These too may have their surface covered with a transparent glaze."
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"Encaustic tiles consist of a slab of clay of uniform color, inlaid with a device of other clays differently colored. In this ware the colors are not superficial, but are incorporated with the body of the clay before burning, either by pugging dry or in the condition of a liquid slip. As to the different coloring ingredients : — Many of the clays which contain less iron, such as the Stourbridge and others in proximity to the coal measures, do not come out of the fire red like brick, but white, cane or buff in all varieties of tint, and stand the attack of fire and weather. Red, salmon and pink will be produced as the iron predominates, altered by mixtures of other clays in their native condition or by oxides of metals. Nickel, for instance, produces a bronze-green tint ; manganese brown ; protoxide of iron and manganese dead black. Carbonaceous matter gives a dark, dull-looking and rather dirty tint, which may be useful in contrast. There is no end to the variety of tints which can be obtained by the admixture of earths and metallic oxides. To economize the inlaid colored clay material, the tile is only formed of it to the depth of about of an inch from the surface, the mass of the tile being made of fire-clay. As, however, the fire-clay generally contracts very differently from the surface layer of colored clays, it is usual to apply to the back of the fire-clay, an equal thickness of about of an inch of the colored clay, in order to preserve the flatness of the tile during the firing. The tile is made with the aid of a press, either by the wet or dry process. By pressing many small holes in the back of the tile, the drying is facilitated, and also the adhesion of the mortar when subsequently used on the wall. The tiles are dried for a week, then heated in a drying oven for two or three weeks, fired in a stone-ware oven for sixty hours, and left in the oven for six days more to cool down. The lineal contraction during these operations amounts, in the wet process, to twenty-nine per cent. of the size of the tile when first moulded. It is less in the' dry process."
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Beckwith, Arthur. International Exhibition, London, 1871: Pottery. Observations on the Materials and Manufacture of Terra-cotta, Stoneware, Fire-Brick, Porcelain, Earthen-ware, Brick, Majolica, and Encaustic Tiles, Remarks on the Products Exhibited. (New York: D. Van Nostrand, 1872.) p 36, 42-43.
