The easiest and fastest way to tell a ceramic tile from a porcelain tile is to take a look at its edge. A ceramic tile, whether for floor or wall use, has a glaze on top of the surface, giving it its color and finish.
Porcelain tiles may be glazed but are frequently not. Even when glazed, the color of the clay body beneath the glaze will be similar in color, and the glaze applied only gives some additional detail to the surface.
Ceramic tiles come in two varieties. Glossy wall tiles have a thin glass-like glaze on top. Textured floor tiles have a matte finish, which has a duller glaze and possibly a slight texture.
Porcelain tiles may be matte, textured, or glossy in finish, but the biggest difference is that the color goes all the way through the tile. If you chip a ceramic tile, the glaze will come off, and the clay body will be exposed. If you chip a porcelain tile, no change in color occurs.
Ceramic tiles come in far more colors and sizes than porcelain, ranging from ⅜-inch mosaic to 16-inch or larger tiles. Porcelain comes in mosaics but usually starts at 2 inches in size, skips up to 6 or 8 inches, then 12 inches. It may eventually reach square sizes of 36 or 48 inches.
Contemporary porcelain tiles may have a wide range of styles, including those that are made to look like wood, fabric, glass, metal, and stone. Ceramic tiles may mimic the look of stone for some floor tiles but generally look like what they are, which is glazed clay tiles.
Ceramic tiles come in two types, monocottura and bicottura. Monocottura means that wet clay is pressed or extruded into the shape of the tile, dried, glazed, and then fired once. Terracotta is an example of a monocottura tile. Bicottura means that wet clay is pressed or extruded into the shape of the tile, then fired until hard. The glaze is then applied before a second firing. A bicottura tile is much harder and more dense than a monocottura tile. However, both forms start out as wet clay.
Porcelain tile is made of clay dust not wet clay. The dust is dyed or pigmented into the desired color, then compacted under extreme pressure, which makes the tile much more dense and durable. The resulting tile is then fired to much higher temperatures than the ceramic tiles, resulting in a non-porous, highly durable tile that can withstand high-traffic areas.