The difference between clay and terra-cotta is that clay is the raw material, while terra-cotta is clay that is already modeled and fired.
Terra-cotta is an Italian term that means "baked earth." Terra-cotta refers to a glazed or unglazed piece of ceramic made using organic clay fired in a potter's kiln.
Objects made on the potter's wheel are called pottery. Terra-cotta also refers to the color of fired earthenware clay that contains a high amount of iron oxide.
The Process of Making Terra Cotta
Terra cotta, also commonly spelled terracotta, is a building material created from clay. This material has been used in architecture and building for thousands of years. Terra cotta has become widely utilized because when compared to other building materials, it is cheap and easy to shape; it is essentially just a clay product fired under specific techniques.
ClayTerra cotta is made from clay. However, different types of terra cotta have different names based on where the product is made. This is partly because clay harvested from the ground in any particular region will have a slightly different makeup than clay found elsewhere. However, wherever the terra cotta is made, the first step is finding suitable clay deposits and harvesting the clay from the ground.
Refining
The raw clay needs to be refined before it is made into terra cotta pots, tiles or other products. This process involves drying the clay and then screening and filtering it to remove impurities that affect the consistency, color and other properties of the clay. Depending on the purity of the clay pit from which the material is removed, raw clay has foreign matter, minerals, rocks and other items that need to be removed during this process.
Molding
Once it has been refined, terra cotta clay is often pressed into molds. Roofing tiles, flooring tiles and architectural embellishments are just a few of the mold types that are used for terra cotta in building material applications. The clay is firmly pressed into the mold so that it takes on the shape before firing.
Firing
Once the terra cotta has been pressed into the appropriate shape, it needs to be fired in order to cook and harden. Terra cotta falls into the category of low fire clay. This means that you must fire it at a lower temperature than many other clays or it will melt. This can damage the kiln as well as ruin the work. Normally, terra cotta is fired at a temperature between 2,048 and 2,079 degrees Fahrenheit.