Tuesday, July 22, 2014

Porcelain Tile vs. Ceramic Tile


Since launching our new line of Porcelain Pool Tile earlier this month, we've been getting a lot of questions about what makes porcelain tile better than ceramic tile. More commonly, the question is simply, "What is the difference between porcelain and ceramic tile?" It’s a question I gladly welcome and one that is fairly easy to answer.

Glazed porcelain tiles, like the blue tiles used for this fountain, are good choice for pools and spas.
Glazed porcelain tiles, like the blue tiles used for this fountain, are a good choice for pools and spas.

Homeowners often discuss ceramic and porcelain interchangeably, as if they were one and the same. To add confusion, tile shop salespeople often extol the superiority of porcelain and claim there is a chasm that separates the two. Porcelain tile tends to be more expensive and this is one reason salespeople will try to "justify" porcelain to those not versed in tile’s technical details.

Porcelain tile is a type of ceramic tile and nothing more. In other words, all porcelain tiles are ceramic tiles; but, not all ceramic tiles are porcelain. Porcelain and ceramic tiles are very similar, especially when compared to cement tiles, quarry tile, glass tiles or stone. Porcelain, by definition, is a ceramic material made by heating materials, including clay in the form of kaolin, in a kiln to temperatures between 2,200 °F and 2,500 °F. Porcelain has high strength and translucence because of the formation of glass and minerals within the fired body at these high temperatures. Porcelain derives its present name from the Old Italian porcellana (cowrie shell) because of its resemblance to the translucent surface of the shell. While all of this might be interesting, it has very little relevance to porcelain tile.

What Makes Porcelain Tile – Water Absorption Rate
A tile can be a porcelain tile IF AND ONLY IF it has a water absorption rate of 0.5% as defined by American Society for Testing and Materials (ASTM) C373. To pass the test, a group of tiles is fired and then weighed. The tiles are boiled for five hours and then they sit in water for another 24 hours. Then, the tile is weighed again. If the tile weighs less than half of one-percent more as a result of water absorbing into its surface, then it is considered porcelain. No cowrie shells here.

Porcelain tile is typically extruded and will have less impurities than ceramic. It may be rectified and usually contains more kaolin than ceramic. However, the defining difference is that porcelain must have 0.5% or less water absorption rate.

Some ceramic tiles, like these decorative Malibu tiles, on the stair risers are rated for freeze/thaw cycles.
Some ceramic tiles, like these decorative Malibu tiles on the stair risers, are rated for freeze/thaw cycles.

Porcelain Tile Certification
Due to confusion and dishonest tile companies, the Porcelain Tile Certification Agency (PTCA) was created to certify tile as being porcelain or not. So, according to the PTCA, a tile has to meet ASTM C373 standards of water absorption to be branded as porcelain. A company does this by sending in five tile samples for testing, paying a fee, submitting a participation agreement, and renewing certification every three years. After certification, a company may use the "Certified Porcelain Tile" branding.

Only a score of North American tile companies have received Porcelain Tile Certification.

Why Tile Water Absorption Matters
Unless explicitly recommended, laying either porcelain or ceramic tile outside is typically not recommended in frosty environments. The primary concern: if the clay bisque or body absorbs water and you live in an area that freezes, your tile will crack when exposed to freeze/thaw cycles. That’s why it's imperative to know if the tile is rated for freeze/thaw cycles. You might argue that a glazed ceramic is imperious to water and it is. However, there is enough latent water in the bisque, often after installing, that can damage the tile when it freezes. If you live in an area, like Los Angeles or the Mediterranean, that is not subjected to hard freezing, then you don’t have to worry about this problem. Avente tiles that are rated for freeze/thaw cycles include:

  • Porcelain Pool Tiles – Plain (solid-color) porcelain tiles that have been freeze/thaw tested. They are great for spas, fountains or any outdoor application.
  • Yucatan Field Tile – Vitreous tiles are another type of ceramic tile that generally absorb very little water. We've used these tiles for projects in Colorado cabins at 7,000 ft. elevations that aren't used in the winter. The tiles are in great shape, year after year!
  • Malibu Decorative Tiles – Decorative ceramic tiles that have been freeze/thaw tested and pay homage to the Spanish Revival period of Los Angeles.
  • Malibu Field Tiles – Plain (solid-color) ceramic tiles that have been freeze/thaw tested and coordinate perfectly with our Malibu decos.

While conventional wisdom has been to keep porcelain or ceramic tile away from the outside, you can see there are lots of options for ceramic tiles that are suitable for exterior use.

Benefits of Porcelain Tiles
Porcelain does offer some benefits that you won’t find with ceramic. However, for most residential application most of these benefits are "gold cladding inside a steel suit of armor." In other words, while true, you probably won’t benefit from them – especially if using a glazed porcelain tile.

Porcelain clay is more dense than ceramic clay. Therefore, porcelain tiles are less porous than ceramic and this makes porcelain tile harder and more impervious to moisture than ceramic tile. The increased density also makes it more durable and better suited for heavy usage than ceramic tile. For instance, unglazed porcelain in a restaurant is the best choice for a hotel lobby or restaurant entry. Unglazed porcelain has through-body composition and color. Chip a glazed ceramic tile and you find a different color underneath the top glaze. Chip the porcelain and the color keeps on going--the chip is nearly invisible.

While both porcelain and ceramic are fired, porcelain is fired at higher temperatures for a longer time than ceramic. Additionally, porcelain has higher feldspar content, which adds to its durability. The strength in porcelain tiles means they resist wear and abrasion and the Porcelain Enamel Institute (PEI) ratings for porcelain tile tend to be at the top of the scale (4-5). The PEI ratings for ceramic tile can land just about anywhere on the scale from 1-5. The PEI ratings is commonly referred to as “abrasion resistance” and is probably the most commonly used industry rating for wear. PEI Ratings of 5 are good for heavy residential and commercial traffic, whereas a PEI 1 is recommended for wall applications only.

Porcelain tile and vitreous tile work well for an outdoor patio subjected to freeze/thaw cycles.
Porcelain or vitreous tile work well for an outdoor counter subjected to freeze/thaw cycles.

Find the Right Tile for the Project
I've had people request decorative porcelain tiles with a PEI 5 rating. I've asked them, "Where are you using the tile?" The customer replies, "On my kitchen wall. I want the best tile!" Different tiles and tile materials are manufactured for different applications to provide the best results. Take into account the application first and also who will be doing the installation. Ceramic tiles are less dense than porcelain tiles and usually a far easier material for homeowners and DIY installers to cut. Porcelain requires experience to cut because it is very hard and brittle compared to ceramic. Remember, ceramic tile will be less expensive than porcelain tile. While porcelain has many benefits, ceramic may the best choice for the job!

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