How are Ceramic Tiles made?

How ceramic tiles are made.
Ceramic tiles used to be made by shaping wet clay by hand, sometimes with a mold then dried either by the sun or a small kiln. There are a handful of artisans that still craft ceramic tiles by hand but the majority of ceramic tiles now go through a process called “dry pressing” or “dust pressing.” The process requires much less labor and makes ceramic tiles affordable to more than just royalty.

Drying

Ceramic tile starts as a clump of earth. Each manufacturer has their own recipe for the tiles but typically the main ingredient is clay with other items such as sand, feldspar, quartz and water. The ingredients are mixed and ground up into a ball mill to create what’s known as the “body slip” which is
still about 30% water. That moisture helps adhere the ingredients to each other and once it completes this task it is put into a dryer and heated until it’s moisture content is reduced to about 6%. After drying out, the body slip becomes essentially powder or dust. The dust is then pressed together into shape with pressure ranging from a few hundred pounds per square inch to a hundred thousand pounds per square inch. This pressure provides the finished project with its tensile strength.

Glazing

Glazing is the process behind the shine of the tile. Glaze can be sprayed or silkscreened onto the tile, finished in matte and high-gloss. Pigments can be mixed into the glaze to color the tile. Though glazing is a standard step for ceramic tile, it’s not essential.

Baking
All ceramic tiles must be baked one way or another. Traditionally, ceramic tile baked for several hours in what’s known as a periodic kiln, such as a beehive kiln. Over the last century however, the continuous kiln has made the production process of ceramic tile more efficient. These new types of kilns are like the conveyor belt pizza ovens.  The tiles roll through the contraption. The heat inside the kiln is precisely monitored and controlled by computer. In the first half of the tile’s journey, maximum temperature can get as high as 2,500 degrees Fahrenheit. The higher the temperature, the stronger the tile.

Slip Class

Depending on the tile’s finish the tile can be slippery when wet. Manufacturers have a rating system that is based on or supported by the American Society for Testing & Materials (ASTM). Many times you can find these ratings on the tile sample or in the product catalog. The most common system rates ceramic tile abrasion, resistance and the overall durability of the tile.

Class 1: No foot traffic

These tiles are suggested only for interior wall applications — not for flooring. Serious slippage.

Class 2: Light Traffic

These tiles are suggested for interior wall applications and residential bathroom floors only. Minor slippage.

Class 3: Light to Moderate Traffic

These tiles can be used for residential floors and wall applications, including bathrooms, kitchens, foyers, dining rooms and family rooms. Slight chance of slippage.

Class 4: Moderate to Heavy Traffic

These tiles are recommended for residential, medium commercial and light industrial floor and wall applications, including shopping malls, offices, restaurant dining rooms, showrooms and hallways. Rare chance of slippage.

Class 5: Heavy/Extra Heavy Traffic

These tiles can be installed anyplace. They will work for both floor and wall applications in airports, supermarkets and subways. Zero chance of slippage.

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