Ceramic (non-porcelain) tiles are thin slabs of red or white clay, in the form of shale, gypsum or sand, converted into a material known as bisque. This bisque is given the shape of tiles and hardened, through the process of firing, in a kiln with averaging temperatures of 2100 degrees F. Since ceramic tiles are porous in nature, they are often coated with glaze. Ceramic tiles are prone to wear and to chipping or cracking on forceful impact. The glaze on the tile does not go all the way through, so the core becomes obvious if the tile is chipped. Ceramic tiles are suitable for light to moderate traffic.
Porcelain is made by pressing porcelain clays and baking at a higher temperature in the kiln than ceramics, averaging 2350 degrees F. The tile is dense, impervious, fine-grained, and smooth with a sharply formed face. The color may run consistently through the body of the tile (full-body) to minimize the appearance of chipping. Glazed porcelain tiles are much harder and have more wear- and damage-resistance than ceramic tiles, making them suitable for any residential and light commercial application. Glazing also results in a porcelain tile usually has a much lower water absorption rate than ceramic tiles, making them more frost resistant.
The Differences Between the Two
Porcelain Enamel Institute (PEI) ratings are given to ceramic and porcelain tiles. There are six class ratings (0 to 5), altogether, which indicate how hard and impervious a tile is. A PEI Class 0 rating suggests a tile is delicate and not suitable for any foot traffic, while a PEI Class 5 rating indicates a tile is very durable and suitable for high foot traffic in commercial areas or perhaps even outdoor use. Most ceramic tiles receive a PEI class rating of 0 to 3, while most porcelain tiles receive a class rating of 4 or 5.
There are three water absorption classifications as defined by the American Society for Testing and Materials (ASTM) to be aware of: Impervious porcelain, vitreous porcelain, and ceramic. Impervious porcelain tile has less than 0.5% water absorption rate, vitreous porcelain being 0.5-3% and ceramic being 3-7%.
This is tested by first, weighing fired tile. Then it is boiled for 5 hours and let to sit in water for 24 hours. Finally, it is weighed again. If the tile weighs less than half of one-percent more as a result of water absorbing into its surface, it is considered impervious porcelain. Any weight increase between 0.5-3% is vitreous porcelain, while ceramic tile gains anywhere from 3-7% in water-weight.
It is important to note that all porcelain is ceramic but not all ceramic is porcelain. Specifically, porcelain is ceramic that has lower water absorption due to a denser body therefore it is ideally suited for outdoor installations.
Ceramic and porcelain tiles can be any color and even made to look like other materials, such as wood or natural stone. However, the design on a porcelain tile is more likely to withstand damage, as porcelain tile design goes throughout the entire tile. Not only is porcelain tile denser than ceramic tile, but due to its through-body composition, it is considered more durable and better suited for heavy usage than ceramic tile. While both porcelain and ceramic are fired, porcelain is fired at higher temperatures for a longer time than ceramic. Porcelain clays are denser and thus less porous than ceramic clays. This makes porcelain tile harder and more impervious to moisture than ceramic tile.