Porcelain Tile vs. Ceramic Tile: Understanding the Differences

For many, the terms "ceramic" and "porcelain" get thrown around interchangeably, as if they were the same. Tile shop salespeople often claim a vast world of difference between the two in order to justify porcelain's higher prices. As it turns out, homeowners are closer to the truth than the tile people. Here's why. The Family of CeramicPorcelain and ceramic tile are essentially the same, with one slight difference. Both are part of the larger category of tiles we can call ceramic. 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. All In The NameAdd a healthy dose of marketing-speak and sales pitch. Tile people often tout 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 porcelain tile. This is different ball game. It's a game of branding and certifying, and has nothing to do with fine china. (And certainly, porcelain tile and ceramic tile can be considered close cousins when discussing other, wildly different types of tile such as quarry tile, glass tile, or natural stone.) So what are the differences? 1. Porcelain Has a Low Water Absorption RatePorcelain 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 OutsideLaying 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 CeramicPorcelain 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 WinsNot 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 PorcelainThe 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 CeramicPEI 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.

Ceramic glaze

Ceramic glaze is an impervious layer or coating of a vitreous substance which has been fused to a ceramic body through firing. Glaze can serve to color, decorate or waterproof an item.[1] Glazing renders earthenware vessels suitable for holding liquids, sealing the inherent porosity of unglazed biscuit earthenware. It also gives a tougher surface. Glaze is also used on stoneware and porcelain. In addition to their functionality, glazes can form a variety of surface finishes, including degrees of glossy or matte finish and color. Glazes may also enhance the underlying design or texture either unmodified or inscribed, carved or painted.

Manufacturing Process

The manufacturing process for ceramic tiles The principal phases are as follows: preparing the raw materials, pressing, glazing, firing, sorting and finally packaging Draw of the processThe manufacturing process starts with the selection of the raw materials that make up the ceramic tile, essentially clays, feldspars, sand, carbonates and kaolins. As the raw materials are normally used exactly as they are extracted from the mines or quarries, it is essential to begin by ensuring that they are homogenised, in order to guarantee that their characteristics are consistent. They are therefore ground in order to disperse and reduce the particles. This grinding process may be wet or dry. Wet grinding is the most common method, whereby the clays are dissolved in water in a ball mill. The resulting suspension is known as ‘slip’. Spray-drying is used to reduce its water content for the later compacting and drying processes. The slip is pumped, sprayed and dried by a stream of hot gases inside the spray-dryer. These gases come from a conventional air-gas burner, or alternatively the exhaust gases from a cogeneration turbine may be used, thereby cutting the cost of the drying process. A spray-dried powder is produced, made up of spherical granules that are uniform in shape and hollow inside, allowing for a fine loose powder which makes the mould-filling and pressing processes easier. Dry pressing is the most common moulding method. Hydraulic presses are used, guaranteeing maximum compaction, high productivity rates and optimum consistency in the press cycle time. The tiles produced have a moisture content of between 5 and 7 per cent, which means they must be dried to reduce it to between 0.2 and 0.5 per cent in order to ensure successful firing, and, where appropriate, glazing. An excessively high water content would cause the tiles to crack or break. In the case of unglazed products, after drying, the next phase is firing. If the tiles are to be glazed, then they must first be covered with one or more layers of glaze. This gives the tiles a series of technical and aesthetic features including colour, gloss and surface texture. Glazed tiles are also impermeable and easy to clean, and are chemically and mechanically resistant. Ceramic tiles are line-glazed and the most common techniques are waterfall glazing, spraying, dry glazing or decorating. Firing is one of the most important stages in the manufacturing of ceramic tiles. During this process, a series of reactions take place that change the microstructure of the tile, creating the required final properties such as mechanical strength, size stability, resistance to chemical agents and fire and easy cleaning. During the firing stage, the key variables in the thermal cycle are the firing time and temperature and the kiln atmosphere, which depend on the composition of the raw materials and the type of product required. Today, fast firing is the most common method used in the production of ceramic tiles. Single layer roller kilns are now used, which have drastically reduced the firing cycle times to less than 40 minutes (thanks to the improved heat-transfer coefficients, as well as their uniform nature and flexibility). In these single layer kilns, the tiles travel over the rollers and the heat needed to fire them is supplied by natural gas-air burners located in the kiln walls. During this process, the heat is basically transmitted by convection and radiation. In order to guarantee maximum quality at each stage of the process, the next stage is to sort the tiles and detect any faulty pieces. Although sorting was originally done by hand, today this process is carried out automatically using recognition software based on a series of pre-determined parameters. This enables tiles that are irregularly shaped or with faulty colouring to be removed. Packing is the final stage in the ceramic tile manufacturing process.

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