Raku Firing - Pat Armstrong

Raku Glaze Firing

Raku is a Japanese technique of glaze firing closely linked to the Tea Ceremony. It involves removing the glazed pot from the kiln when the glaze is molten (around 900 degrees Celsius). The glazed pot is then put in a reduction chamber and covered with sawdust. This action gives the typical black crackle.

Copper Fuming

Copper fuming is achieved by the application of a 90% copper oxide and 10% glaze mixture onto the surface of the pot, which is then fired in the normal Raku way. This gives beautiful vibrant colours and a velvet texture finish (sometimes). It is notoriously difficult to control.

Naked Raku

This term is given to the pots which have had the glaze removed after firing. To make this possible the pots are coated with slip (liquid clay) at leatherhard stage and burnished with pebble until shiny. The pot is biscuit-fired in the normal way. A second slip is then applied to the pot and after 24 hours it is glazed. After Raku firing the pot is removed from the reduction chamber and the glaze will (hopefully) come away easily. Black crackle marks are then revealed. The residue of slip is removed and a coating of wax is applied to protect the pot.
Because Raku is a low temperature firing technique the body does not fully vitrify and even the glazed pots may be porous. If one is required to hold water then it is suggested a plastic bottle be cut to fit and inserted inside the pot. This works very well. Also, strong sunlight may fade the carbonisation - it is (as one well know Raku potter suggested) best to treat Raku pots as you would a fine painting.