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!