The Science of Raku What makes fire Fire

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!