Tile (nonfiction)
A tile is a thin object usually square or rectangular in shape. Tile is a manufactured piece of hard-wearing material such as ceramic, stone, metal, baked clay, or even glass, generally used for covering roofs, floors, walls, or other objects such as tabletops. Alternatively, tile can sometimes refer to similar units made from lightweight materials such as perlite, wood, and mineral wool, typically used for wall and ceiling applications. In another sense, a tile is a construction tile or similar object, such as rectangular counters used in playing games (see tile-based game). The word is derived from the French word tuile, which is, in turn, from the Latin word tegula, meaning a roof tile composed of fired clay.
Tiles are often used to form wall and floor coverings, and can range from simple square tiles to complex or mosaics. Tiles are most often made of ceramic, typically glazed for internal uses and unglazed for roofing, but other materials are also commonly used, such as glass, cork, concrete and other composite materials, and stone. Tiling stone is typically marble, onyx, granite or slate. Thinner tiles can be used on walls than on floors, which require more durable surfaces that will resist impacts.
Manufacture
Cavity mold
To make a cavity mold, make an original tile with the design of your choice out of clay, avoiding undercuts. Make the walls for the mold around a board that measures 1 1/2 inches larger than your tile on all four sides (use laminated wood as this eliminates the need for a mold release). Fasten the boards together with four spring clamps or C-clamps. If the boards are all cut accurately at right angles, the assembled form will keep plaster from leaking without the need to seal the joints with clay. Put a wad of clay on the outside of the base of each wall to keep the form secure. Rub some water on the bottom of your original tile to create a thin slip and stick it to the bottom board allowing a 1 1/2-inch border around all sides.
Pour the plaster at least 1 1/2 inches over the top of the tile – any less and the mold may crack during pressing. For most studio applications, I use #1 Pottery Plaster. Make sure the plaster is fresh (stored for no more than 6 months) and completely free of moisture.
Measure room-temperature water and plaster by weight in a ratio of 0.7 parts water to 1 part plaster. Use 1 lb water to 1.4 lb plaster for a 4 1/2-inch square mold and 2.1 lb water to 3 lb plaster for a 6 2/3-inch square mold. Note: I’ve used decimals not ounces.
Slowly sift the plaster into the water.
Once all the plaster is in, allow it to soak (slake) for one minute without any agitation. Mix the plaster with a clean stick until it becomes a heavy cream consistency (a milkshake consistency is too thick). This should ideally take 2 to 3 minutes, but can happen anywhere from 1 to 5 minutes.
When the plaster has reached a proper consistency, pour it into the form in a slow steady stream.
Shake the table (but not too much) to bring any air bubbles to the surface, and to settle the plaster out, making the top completely flat.
Swirl some water in the dirty mixing container immediately and dump it into a waste bucket (never down the drain!).
When plaster sets, it gives off heat. After about 30 minutes it will cool back down and you can then take the form apart. If the boards stick give them a quick tap away from the mold and they will pop off.
To use the mold, cut a slab of clay the same size as the opening. Cover the clay with canvas and use a rubber mallet and a block of wood to press the clay into the mold.
Use a wire cutter to slice off the excess clay. The homemade wire tool shown at right is based on one used at Moravian Pottery and Tile Works (where I had attended a workshop).
Use a wooden straight edge to scrape off and level the back of the tile. You may want to sign or stamp the back at this point. Give the clay some time to set. This may vary greatly depending on the weather and dampness of the mold.After the clay has set up to about leather hard, you should be able to easily pop it out of the mold.