Preset Cone Fire Programs - Orton AutoFire Plus User Manual

AutoFire® Kiln Controller
Lo Fire
Decals or lusters are normally applied following the second or third firing. They add to the final beauty and
value of the object. These firings are done at low temperatures, around Cone 019, and normally produce a
distinct odor. Firings can be made relatively fast. The presence of oxygen throughout the firing is essential.
Good ventilation of the kiln is also necessary, as oils and other organic materials are burned off. Some decals,
lusters, and gold have a limited firing range. If too large of a temperature distribution exists inside the kiln, the
firing capacity or load placement must be altered or limited.
The preset firing program for Lo Fire is shown below. The standard firing time is about 3 hours, 20 minutes
depending on load and other variables.
540 °F/hour (300°C/hr) for about 2 hours
108 °F/hour (60°C/hr) for about 1 hour, 20 minutes
The firing speed based on load size adjustment will vary the firing times from about 2 hours, 40 minutes to
about 4 hours, 10 minutes.
Mid Fire
This firing range is used to fire earthenware and packaged glazes. When glazes are applied to a bisque body
that has already been fired, the firing can made be relatively fast. The ware should be thoroughly dried prior to
firing. The heating rate is slowed during the quartz phase change, 1063 °F (573 °C). Air is needed in the kiln to
develop bright shining colors, such as reds and yellows, so venting is particularly important. Slow firing rates
can produce poor quality glazes. With lead-free glazes, a 10-15 minute hold is beneficial. Cooling too fast can
produce glaze defects such as pinholes, blisters, and craters.
When earthenware or other bodies contain ball clays, talc, and kaolin, then compounds such as water, carbon,
and sulfur will be burned-off during the firing. In addition, a phase change (physical change) in any silica
present must be considered and the heating rate slowed during this reaction which occurs near 1063°F (573°C)
or cracking can occur. This phase change occurs during both heating and cooling.
During the firing, the material will loose about 10 percent of its weight. This weight loss occurs due to:
• Water coming off between room temperature and 212 °F
• Binders coming off between 300 °F and 500 °F
• Chemically combined water coming off around 900 °F to 1000 °F
• Carbon and sulfur coming off between 1100 °F and 1600 °F
• Carbon dioxide evolving from calcite and dolomite around 1700 °F
The preset firing program for Bisque firings is shown below. The standard firing time is 7 hours, 30 minutes.
360 °F/hour (200°C/hr) for 2 hours, 20 minutes
180 °F/hour (100°C/hr) for 1 hour
297 °F/hour (165°C/hr) for 2 hours, 40 minutes
108 °F/hour (60°C/hr) for 1 hour, 30 minutes
The firing speed based on load size adjustment will vary the firing times from about 5 hours, 40 minutes to
about 9 hours, 20 minutes.

PRESET CONE FIRE PROGRAMS

User's Guide
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