150°C-650°C (3 hours)
Short pieces of wood are used to avoid flame in the kiln. Only a slight draft is allowed through the kiln (i.e. several of bricks are removed from the base of the chimney to reduce its pull).

800°C-900°C (2¹/₂ - 3 hours)
Very slow and 'clean' burn to give time for trace impurities in the clay (e.g. compounds of Carbon & Sulphur) to burn out. Failure to achieve this will probably result in bloats (see NOTE at end).

900°C-1050°C (1¹/₂ hours)
No likely problems.

± 1050°C (1 hour)
Reduction (see note 2) achieved by constricting the chimney so that the chamber fills with smoke. Stoking only enough to achieve this. The temperature will fall during this time but over stoking causes further fall in temperature.

1050°C-1300°C (3 hours)
Maximum draft up the chimney. This is a clean burn phase and all of the elements are fully oxidised.

~1280°C (half an hour)
The soak - were the temperature is held steady

Temperature
Monitored by digital pyrometer checked by the use of cones (at the reduction temperature and approaching the top temperature)

Wood

• Offcuts from sawmill used.
• Mostly split for faster burn (e.g. 1" & 3")
• Short stocky pieces used at the start to avoid flame into the kiln
• About ²/₃ ton required.

The pots are 'raw glazed' or 'single fired' i.e. there is no 'bisc.' firing, for this reason the slight impurities in the body have to burn out before vitrification begins at about 1000°C. If this is not done the finished product is likely to have 'bloats' - i.e. blisters caused by trapped impurities.

The reason for caution at the early stages is that even though the kiln temperature may read 600°C the hot face temperature due to flame can easily approach 1000°C and so cause localised sealing of the surface (vitrification) resulting eventually in bloating.

NOTE 2

Reduction - A chemical term meaning that oxygen is removed from the glazes and clay body. This is achieved by starving the kiln of oxygen before the surface begins to vitrify. Reduction alters the colour of the body and of the glazes causing them appear 'softer' or more subdued.