What happens to clay in a kiln?

When pottery is placed into the kiln, it is almost always bone dry. However, there is still water trapped within the spaces between the clay particles. As the clay is slowly heated, this water evaporates out of the clay. This will result in the clay compacting and some minimal shrinkage.

Is Firing clay a chemical reaction?

Firing Clay Explained. Clay goes through several physical changes when fired. The first step is the evaporation of water from between the clay particles. Once this chemical change has taken place, the process cannot be reversed and the clay cannot be returned to its plastic state.

What happens to the clay used to make pottery when it is baked in a kiln?

Heat removes the molecular water in the clay. The heat converts clay molecules to molecules that do not dissolve or slake in water. In modern societies pottery and brick is fired in kilns to temperatures ranging from 1,800 F to 2,400 F. It is fired to 2,300 to 2,400 F., making it very strong and impervious.

What does heated clay turn into?

The purest clay is made of the mineral kaolinite, KAlSi3O8. Ceramic clays also contain quartz and feldspar minerals. 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.

Why does clay explode in the kiln?

When the clay is thicker, it can feel very dry on the outside while the inside still contains moisture. When the kiln temperature rises, the air pockets fill with water vapor, which builds pressure as water turns to steam. The pressure of the steam causes the clay to explode from the inside.

At what temperature does clay melt?

Clays vitrify at various temperatures depending upon their composition. A red clay high in iron and other impurities might fire to hardness at about 1000 degrees C (1832 degrees F) and melt to liquid at 1250 degrees C (2282 degrees F).

Is clay called ceramic after it is fired in the kiln?

Clay is normally fired twice. After the first firing, the clay is called ‘ceramic’. The first firing is called the bisque fire, and the clay becomes bisqueware. The second fire is the glaze fire, and this clay is called glazeware.

How does clay decay?

Like stone, clay is a chemically decomposed igneous rock, by firing the pottery we turn the clay back to a state similar to original state. Over time it will weather and decompose just as stone does but this usually takes a very long period of time.

How do you heat clay?

For Original Sculpey, preheat to 275 degrees F (135 C). Bake for 15 minutes per quarter inch of thickness. For example, a piece of 1/2″ thickness should be cured for 30 minutes. For Super Sculpey, preheat to 275 degrees F (135 C).

What happens when you heat up mud?

As you can probably guess, heating mud that contains organic matter is just going to cause that organic matter to combust and decompose. If you do this in a pottery kiln, the combustion will be incomplete, producing carbon monoxide and leaving you with char.