Porcelain and ceramic tile offer a wide variety of colors, textures, and patterns. Kiln-fired porcelain and ceramic tile are made from a mixture of clays and minerals which create a stable, durable, and versatile surface. Available in a variety of designs, it’s easy to find a ceramic or porcelain tile option that best serves your purpose.
Porcelain and ceramic tile has seen a variety of uses over the years, going as far back to Ancient Egyptian times, and continues to be a feature in many homes; from plain unadorned tiles in a wide range of colors, to those that mimic the look of stone or marble.
Porcelain and ceramic tile offer a number of significant benefits:
- A wide selection of colors, textures, designs, and styles
- Durability
- Heat and fire-resistance
- Will not fade when exposed to direct sunlight
- Low-maintenance
- Porcelain tile can be used in wet areas and areas where moisture is expected - kitchens, bathrooms, and pool areas.
- Resistant to abrasion wear and tear, making them a great choice for areas with high traffic.
- Slip-resistant quality of unglazed tile
In addition to their use as floor surfaces, porcelain and ceramic tiles are also used for walls (interior and exterior), roofs, balconies, patios, and countertops.
How Porcelain and Ceramic Tiles Are Made
The processes of making ceramic tile starts with mixing raw materials such as clay, and naturally present minerals. Sometimes water is added (a process called wet milling) but is later removed when actually making the body of the tile. Every type of ceramic or porcelain tile is the result of a kiln-firing process. There are two types of firing processes: monocottura and bicottura.
- Monocottura; individual ceramic tiles are fired and glazed at the same time. This produces a denser and more durable ceramic tile.
- Bicottura, on the other hand, is a two-step firing process. The clay is fired once, and then once again with a glaze added to the top layer of ceramic tile.
What Makes Porcelain Tiles Different From Ceramic Tiles?
Porcelain tile is a kind of ceramic but made with finer grain clay, and fired at higher temperatures in the kiln. It is a very hard tile option, and resistant to wear and tear, and completely moisture-resistant.
PEI Rating
The PEI (Porcelain Enamel Institute) rating is a system of classifying tiles based on how well a tile will perform in a specific area and under certain expected conditions – moisture levels, traffic, and abrasion. The PEI rating is assigned after the results of a series of tests on the tiles have been performed. Here are the ratings:
- Class 1 –suitable for use in interior commercial and residential walls. They are not meant to be used for flooring.
- Class 2 – interior commercial and residential walls, as well as low-traffic residential floors; areas where softer footwear is generally worn.
- Class 3 – interior commercial and residential walls, countertops, and residential floors
- Class 4 – all residential and most commercial applications that have moderate to heavy traffic such as reception areas, boutiques, interior walls, countertops, and residential floors
- Class 5 - tiles as classified 4+ are best used in areas with extra heavy traffic like shopping malls, public buildings, and building entrances
Water Absorption Ratings for Porcelain and Ceramic Tile
The water absorption rating gauges the capacity of water absorption of the body of each tile.
- Non-vitreous –an absorption rate of 7-20% of the total weight of the tile.
- Semi-vitreous –3-7%
- Vitreous – 0.5-3%
- Impervious – an absorption rate of less than 0.5%
"Impervious" Porcelain tile.
Porcelain tiles receive the impervious water absorption rating. This makes it a staple in wet areas like bathrooms, front entrances, and laundry rooms. Unglazed porcelain tiles are also popular as outdoor tiles, being:
- slip-resistant
- water-proof
- frost-resistant and resistant to shifts in temperature
Glaze Hardness of porcelain and ceramic tile
A tile's glaze hardness is determined by the Mohs scale scratch test. The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material.
Most ceramic tile glazes can be scratched by case hardened steel, which is used in drill bits. Case hardened steel falls on #6 on the scale, and so the hardness of most tile glazes must fall between the 5-6 range.
Certain features of ceramic tile can also account for its glaze hardness, such as:
- the temperature at which it was fired in the kiln – the higher the temperature, the harder the tile
- tile color – lighter colors are harder than darker ones
- tile gloss level – matte and satin finishes are harder than high-gloss
Color Shade Variation Grading of Porcelain and Ceramic Tile
Color shade variation grading, which classifies porcelain and ceramic tiles according to variation in color, texture, and tone between individual tiles. The gradings are as follows:
- V1 (uniform appearance) – there is minimal to no difference among pieces
- V2 (slight variation) – there are distinguishable differences in texture and/or pattern within similar colors of tiles
- V3 (moderate variation) – the amount of colors on each piece may vary significantly
- V4 (random or dramatic variation) – there are random color variations from tile to tile, therefore the look of resulting installations will be unique
Skid Resistance Scale
Yet another important consideration when choosing ceramic floor tile is that of slip resistance. The Skid Resistance Scale will help you determine the degree of slippage on a tiled surface. Along with the PEI rating, knowing which skid resistance category your ceramic tiles fall under will help you determine the proper area to install your chosen ceramic tile. All tiles must meet or exceed general safety and health regulations, ADA, and OSHA requirements.
- Slip Resistant – the coefficient of friction is 0.60 or greater when wet
- Conditionally Slip Resistant – the coefficient of friction is 0.50 to 0.59 when wet
- Questionable – when a tile has a coefficient of friction less than 0.50
It is important to note that the more textured the tile is, the less slippery it will be; and the greater the anti-slip finish, the more difficult it is to keep clean.
One may also employ the Pendulum Skid Resistance Test. It is also used to measure the dry and wet slip resistances of floor surfaces, as with the skid resistance scale. They offer the following values:
- <25 – very slippery
- 26-35 – average
- 35-65 – good skid resistance
- 66+ - excellent skid resistance