The Science of Raku

What makes fire?

• Fire happens through a process called combustion

• You need three things for combustion

• Do you know what they are?

Fuel

• You need something that will ignite

• Anything that can burn can be a fuel

• Wood, paper, oil, leaves, coal

Heat Source

• You need something hot to make the fuel start on fire

• We use the glowing hot pots

Oxygen

• Fire needs air to breathe or else it won’t stay lit

• Fire uses oxygen just like you and me!

What makes the glaze colors?

• The main color in raku glazes comes from a metal called copper

• Where can you find copper?

In Pennies…

The Statue of Liberty

What makes the color of copper change?

• A chemical process called oxidation

• Copper starts out the orange color like in a new penny

• When copper is exposed to lots of oxygen in the air over a long time it turns green like the statue of liberty

Normal Copper Oxidized Copper

Oxidation and Reduction

• In the kiln the copper doesn’t get oxidized, it gets reduced

• The fire consumes the oxygen in the trash can and changes the color of the glaze

• The reduced part of the pot will look red or like a copper penny

• The oxidized part of the pot will be green or turquoise

Which side was reduced?

Which side was oxidized?

What makes the white glaze crackle?

• The crackle comes from thermal shock

• Thermal shock happens when a temperature changes from one extreme to another

• The kiln is glowing red hot, but outside the air is much colder

• This shocks the glaze and makes it crackle!

Where else can you see thermal shock?

Ice Cubes!

• When you drop a frozen ice cube into a glass of water it creates thermal shock too!

• The ice is so cold inside a freezer, but the water isn’t as cold

• Thermal shock makes the ice cubes crack just like the white crackle glaze

• This is only a small part of raku science

• Get ready to learn even more when we fire YOUR pots!