Raku is a firing process before it is a clay, and the clay exists to survive the process. Work is taken out of the kiln glowing and put straight into combustible material, which is a thermal shock that would shatter an ordinary body. A raku clay is built open and heavily grogged so it can take it.
What the process does to the pot
A raku firing goes fast, the kiln is opened at temperature, and the piece is moved with tongs into sawdust or paper that catches immediately and is then smothered. That reduction blackens the unglazed clay and pulls copper in a glaze towards metallic lustre. The whole exchange takes minutes rather than the hours of a conventional firing, and every part of it is thermal shock.
Why the body has to be open
Grog and coarse particles leave a network of small gaps through the body, which lets it expand and contract without building the stresses that crack a dense clay. That is why raku clay is coarse in the hand and why a smooth throwing body should not be substituted for it. The same openness leaves the fired ware porous, which is why raku is decorative rather than functional ware.
What it costs, and why
Raku bodies sit at the expensive end of most price lists: CTM's list prices a raku clay well above its stoneware and earthenware bodies per bag. That reflects the materials and the smaller volumes sold rather than anything mysterious. Because raku work tends to be individual pieces rather than production runs, the higher price per kilogram matters less than it would on a throwing body.
The safety part, which is real here
Raku is the one process in this hobby with a fire and burn risk rather than a dust risk. It happens outdoors, with tongs, gloves and a fire-resistant surface, away from anything that can catch, with the reduction bin lidded and controlled. Nothing about that is unusual to anyone who has done it, and it is stated here because raku is often someone's first firing rather than their hundredth.
Questions people ask about raku
Can I use ordinary stoneware for raku?
Usually not. A dense body cracks under the thermal shock. Raku clays are open and grogged specifically to survive it.
Is raku ware food safe?
No. The body stays porous and the surfaces are not sealed, so raku is decorative. This site never describes a glaze as food safe except by quoting a manufacturer's data sheet.
What temperature is a raku firing?
Much lower and much faster than stoneware, typically in the region printed on the body, often quoted from around 900 degrees upward.