Ceramic tile is made primarily from natural clay mixed with minerals like feldspar, quartz (silica), and water, then shaped and fired in a kiln at high temperatures. The exact recipe varies depending on the type of tile, but every ceramic tile starts with some form of clay as its base material, combined with other earth-derived ingredients that control how the tile looks, feels, and performs.
The Core Ingredients
Clay is the foundation of all ceramic tile. Two types of clay dominate tile production: kaolin and ball clay. Kaolin is a relatively pure, white clay that gives tiles their structural backbone. During firing, the minerals in kaolin transform into a crystalline structure called mullite, which is what makes the finished tile strong and rigid. Ball clay is darker, finer-grained, and more plastic, meaning it’s easier to mold into shapes. It provides the workability that lets manufacturers press or extrude clay into flat, uniform tiles. Ball clays also contribute to the mechanical strength of the tile before it even enters the kiln, holding the shape together during drying.
The best ball clays for tile production have very fine particles and high surface areas, which help them bind tightly. After drying, a quality ball clay body can resist bending forces of 3 to 10 megapascals, enough to survive handling and transport into the kiln without cracking.
What Feldspar and Silica Do
Clay alone won’t produce a durable tile. Feldspar and silica (quartz sand) are added as “fluxes,” materials that melt at lower temperatures and essentially glue everything together during firing. In porcelain stoneware tiles, fluxes make up 50% to 60% of the total weight. Sodium and potassium feldspars are the most common choices.
When the kiln reaches peak temperature, feldspar melts into a glassy liquid that fills the tiny gaps between clay particles. As the tile cools, this glass solidifies and locks the structure into a dense, hard body. Silica reinforces this effect, contributing to the tile’s final hardness and helping it resist scratching. Unglazed ceramic tile rates about a 5 on the Mohs hardness scale (comparable to a steel knife blade), while glazed ceramic tile reaches about a 6, roughly the hardness of window glass.
For the clay body to fire cleanly, especially for light-colored tiles, impurities need to stay low. Iron oxide should be no more than 1.5%, titanium dioxide no more than 1.0%, and organic carbon less than 0.2%. Higher levels of iron, for instance, would turn the tile body reddish-brown, which is fine for terracotta but undesirable in white porcelain.
How the Glaze Is Made
Most ceramic tiles sold for walls and floors have a glaze layer on top: a thin, glass-like coating that adds color, pattern, and water resistance. Glaze is made from a separate set of ingredients, starting with frit. Frit is a pre-melted glass that’s been cooled and ground into a powder. It’s produced from silica, feldspar, calcium carbonate, zinc oxide, alumina, and boric acid. These raw materials are melted together at very high temperatures, then rapidly cooled to form small glassy granules.
To make the final glaze, manufacturers mix this frit with crystalline minerals, a small amount of kaolin for suspension, pigments for color, and water. The mixture is ball-milled into a fine liquid slurry and sprayed or poured onto the tile surface before the second firing. In the kiln, the glaze melts, flows smooth, and fuses permanently to the tile body. Some glazes are designed to crystallize as they cool, producing a matte, satin, or textured finish rather than a glossy one.
Shaping: Dust-Pressing vs. Extrusion
There are two main ways to turn raw materials into a tile shape. The method used affects the tile’s density, texture, and typical application.
Dust-pressing is the dominant technique for most ceramic floor and wall tiles. The blended raw materials are dried to a near-powder consistency, then poured into a mold and compressed under enormous pressure. This produces tiles with sharp edges, consistent thickness, and a smooth, uniform surface. The process dates back to at least the 1840s, when it was used to make encaustic tiles with inlaid decorative patterns. A thin layer of colored clay dust was pressed into a mold with a relief design at the bottom, creating the pattern as part of the tile body rather than painting it on top.
Extrusion works differently. A wetter clay mixture is forced through a die (like a pasta maker) to create a continuous ribbon of clay, which is then cut to size. This method produces quarry tiles and other thick, rustic-style tiles. Extrusion ensures uniform thickness and works well for tiles that don’t need a perfectly smooth face. Quarry tiles, originally made from quarried stone, are now almost exclusively produced this way.
Ceramic Tile vs. Porcelain Tile
Porcelain tile is technically a type of ceramic tile, but it’s made with finer, more purified clays and fired at higher temperatures. The key difference comes down to density. Under the ANSI A137.1 standard, a tile qualifies as porcelain only if its water absorption rate is 0.5% or less, measured by weighing the tile before and after soaking. Standard ceramic tiles absorb more water, typically between 3% and 7%, because their body is more porous.
This difference matters in practice. Porcelain’s extremely low absorption makes it suitable for outdoor use, freeze-thaw climates, and wet areas like showers. Standard ceramic tile works well for indoor walls, backsplashes, and dry-area floors, but its higher porosity means it can crack if exposed to freezing water. Both types start from the same family of raw materials. Porcelain simply uses a more refined version of that recipe, fired harder and longer to eliminate nearly all internal air pockets.
What Gives Tiles Their Color
The natural color of a ceramic tile body depends on the clay used and its mineral impurities. Red and brown tiles get their color from iron oxide in the clay. White and cream tiles come from low-iron clays like kaolin. Beyond the body color, the glaze layer is where most visual variety happens. Metal oxides serve as pigments: cobalt produces blue, chromium creates green, iron yields yellow to brown, and manganese gives purple-brown tones. These are mixed into the glaze slurry before application.
Unglazed tiles, like traditional quarry tile or some porcelain, show only their body color. Their appearance is consistent all the way through, which means chips and scratches are less visible. Glazed tiles, by contrast, have their color and pattern only on the surface. A deep chip will reveal the differently colored clay body underneath.