For many of us, the terms "ceramic" and "porcelain" are used interchangeably, as if they were the same thing. Tile shop sales people often claim a vast world of difference between the two in order to justify porcelain's cachet--and its higher prices.
As it turns out, the common idea of these materials is closer to the truth. Ceramic and porcelain are composed differently and do behave accordingly upon installation--but with only slight differences, the chief difference being that porcelain is more impervious to water infiltration than ceramic.
All Part of the Family of Ceramic
Porcelain and ceramic tile are both are part of the larger category of tiles we can call ceramic. For modern tile specifications, it is more a case of reverse-naming, whereby manufacturers take tiles that have certain qualities and then assign the ceramic or porcelain titles to them.
Add a healthy dose of marketing and branding. The tile industry touts porcelain's storied history, evoking its Italian etymology--porcellana, which means cowrie shell. Fine porcelain-ware is white, translucent, strong, and it has a fine, dense body. They mention how fine china is made of porcelain.
But none of that applies to the commodity porcelain tile of today. This is different ball game--a game of branding and certifying, and has nothing to do with fine china anymore. Certification is more than just protecting manufacturers' interests: it's a shortcut that consumers can use to quickly identify which types of tiles they are getting.
Let's break down the differences, point by point:
1. Porcelain Has a Low Water Absorption Rate
Porcelain tile has a water absorption rate of 0.5% as defined by American Society for Testing and Materials (ASTM) C373.
First, fired tile is weighed. Then it is boiled for 5 hours and let to sit in water for 24 hours.
Next, 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 porcelain.
Porcelain tile is often extruded; has fewer impurities than ceramic; is often rectified; and often contains more kaolin than ceramic. It is formed of quartz, clay, and feldspar that is fired at temperatures ranging from 1200-1400 degrees C.
But since that also defines many ceramics, again the difference is that porcelain has that 0.5% or less water absorption rate.
2. Porcelain Is Certified So That It Can Be Called "Porcelain"
Due to confusion from overzealous (or dishonest) tile companies and their marketing departments, The Porcelain Tile Certification Agency (PTCA) certifies tile as being porcelain or not.
So, according to PTCA, it is not simply enough for a tile to be "impervious" (a favorite tile term, meaning that it is good against water); it has to meet those ASTM C373 standards of water absorption 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.
At last count, only 28 North American tile companies had received certification as producing authentic porcelain tile.
Interior or Exterior: No Ceramic Outside
Laying porcelain or ceramic tile outside is typically not recommended. Ceramic is usually not durable enough for exterior use because it absorbs too much water. If you live in areas which freeze, your tile would likely crack on the first freezing night. Stone is a better option.
Even though conventional wisdom has been to keep porcelains/ceramics away from the outside, I'm seeing more that are for exterior use. I would still recommend buying porcelain that is expressly designated for exterior use.
Density: Porcelain Denser 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.
Durability: Porcelain Wins
Not only is porcelain tile more dense than ceramic tile, but due to its through-body composition, it is considered more durable and better suited for heavy usage than ceramic tile. Chip the 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. Also, porcelain has higher feldspar content, which makes it more durable.
Ease of Cutting: Ceramic a Softer Cut Than Porcelain
The aforementioned density has a good side and a bad side. While ceramic is less dense than porcelain, it's also a far easier material for DIY homeowners to cut--by hand, by wet tile saw, or snap tile cutter. Porcelain is more brittle and may require the experienced hand of a tile-setter to cut properly.
Which One Is Cheaper?
All other factors equal, ceramic tile is cheaper than porcelain tile.
- In a survey of porcelain and ceramic tiles at a major online tile retailer, I found that, on average and across all sizes, porcelain costs $5.20 as opposed to $3.24 for ceramic. Translated, this means that ceramic tends to be about 62% of the cost of porcelain.
- In fact, only the top 15% or so of the highest priced tiles from each group roughly matched. Going below that top 15%, prices began to dramatically diverge.
Unless there is some anomaly in pricing, ceramic tile will always be cheaper than porcelain tile. But again, you need to consider other factors in your choice of tile, not solely pricing.
PEI Rating: Porcelain Higher Than Ceramic
PEI ratings for porcelain tile tend to be around 5 (heavy residential and commercial traffic). PEI ratings for ceramic tile can range anywhere from PEI 0 (no foot traffic) up to PEI 5, but with most ratings in the lower end of the scale.