What happens to clay during firing?

When the water content of clay is driven out during firing, the clay body loses a bonding agent. The clay particles are no longer being held together by water. However, the point in the firing schedule where clay has lost its water content is when another bonding process begins. This process is called ‘sintering’.

Is clay hardening a chemical change?

A physical change happens when matter changes size, shape, or form. You can make physical changes to clay by molding it into a pot or flattening it out. The substance is still clay—its shape is just different. The substance also has some of the same properties.

What happens when clay is heated?

As the clay is slowly heated, this water evaporates out of the clay. If the clay is heated too quickly, the water will turn to steam right inside the clay body, expanding with an explosive effect on the pot. This will result in the clay compacting and some minimal shrinkage.

What happens during the first clay firing?

Bisque firing refers to the first time newly shaped clay pots, or greenware, go through high-temperature heating. If it is heated too quickly, the water turns into steam while inside the clay body, which can cause the clay to burst.

What is the chemical structure of clay?

Clay minerals are composed essentially of silica, alumina or magnesia or both, and water, but iron substitutes for aluminum and magnesium in varying degrees, and appreciable quantities of potassium, sodium, and calcium are frequently present as well.

What happens when clay explode in the kiln?

The main reason that pottery explodes in the kiln is residual moisture left in the clay body even when it appears bone dry. Once the kiln reaches 212F, the moisture starts to turn into steam. It expands very rapidly and the pottery shatters to accommodate the steam.

Why does clay harden when fired?

The purest clay is made of the mineral kaolinite, KAlSi3O8. During the heating (firing) process to about 1400 degrees F, the feldspars melt, along with some of the quartz (silica), to form a glass phase that bonds the clay and silica into a durable ceramic.

How are chemical reactions used in pottery?

In ceramic glazes and vitreous ceramic clay bodies, the alkaline and acidic oxides react together and melt. The alkaline metal oxides are fluxes, which react with the acidic glass former, silica.

What are the firing stages of clay?

The Stages of Firing Clay

• Stage 1 – Drying Your Pottery.
• Stage 2 – Bisque Firing Pottery.
• Stage 3 – Glaze Firing Pottery.
• Final Thoughts on the Stages of Firing Clay.

What is the chemical formula of clay mineral?

Like all phyllosilicates, clay minerals are characterised by two-dimensional sheets of corner-sharing SiO 4 tetrahedra or AlO 4 octahedra. The sheet units have the chemical composition (Al, Si) 3O 4.

What is the metallic constituent of clay?

Aluminium silicate is the main Chemical constituent of clay.

What happens to H2O in Clay Firing?

At earlier stages, mechanically bound pore water, that is water between clay and mineral particles, is expelled. However, H2O is bound right into the clay crystal itself, as well as into other minerals that may be in the clay body. For example, kaolin loses 10\%+ of its weight on firing due to this crystal water.

What happens to clay in a kiln when fired?

As the temperature in the kiln goes up, the clay undergoes a lot of significant chemical and physical changes. Here are some of the changes that occur at different points in the bisque firing process: Residual moisture in the clay, called mechanical water evaporates. Organic carbons and sulfur burn out of the clay.

What are the different types of firing of clay?

1 Bisque Firing. Bisque firing refers to the first time newly shaped clay pots, or greenware, go through high-temperature heating. 2 Clay Transformation in the Bisque Firing. When a kiln reaches about 660 degrees Fahrenheit, the chemically bonded water will begin to be driven off. 3 Glaze Firing.

What is the firing process of ceramics?

The Firing Process for Making Ceramics 1 Bisque Firing. Bisque firing refers to the first time newly shaped clay pots, or greenware, go through high-temperature heating. 2 Clay Transformation in the Bisque Firing. When a kiln reaches about 660 degrees Fahrenheit, the chemically bonded water will begin to be driven off. 3 Glaze Firing.