Porcelain tiles are composed of porcelain clays, which are more resistant to water than typical clay. Porcelain tiles are stronger and absorb less water than non-porcelain ceramic tiles, which makes the tiles a good choice for indoor and outdoor areas. Glazing is a technique applied to tiles to make them colored, glossy and protected from stains.
Porcelain is the name given to tiles that contain special clay that makes the tile resistant to water absorption. These tiles have a water absorption of less then 0.5% in order to be classified as porcelain. Porcelain is also stronger than other types of non-porcelain ceramic tiles and therefore it can be more difficult to cut through.
Liquid glass is applied to tiles and then heated with fire to create a glazed surface. Glazed tiles are shiny and can be made in a variety of colors. The glaze can be colored so that the surface of the tile has a different color than the body underneath the glaze. Glazed tiles are nonporous. Unglazed tiles do not have the protective, shiny layer like glazed tiles.
Since glazed tiles are nonporous, they resist stains. If a liquid is spilled onto a glazed tile it will not soak into the clay below, whereas on an unglazed tile the liquid can permeate the tile and stain the surface.
Brands of tiles are all rated for how well they hold up to wear and tear. In general, unglazed tiles show less wear than glazed tiles. Unglazed tiles are the same color throughout the body of the tile so that wear on the surface does not show since the color is the same. With a glazed tile, the surface of the tile is often a different color than the body of the tile. When wear occurs on the surface of a glazed tile, it can wear away the glaze so that the different color in the body of the tile shows through.
Unglazed tiles have a rougher surface than smooth, glazed tiles. The rougher surface allows for better traction when walking so that unglazed tiles offer better slip resistance than glazed tiles.