How to Choose the Right Bisque Firing Temperature

What is the best bisque firing temperature? For many pottery clay bodies, Cone 06 to Cone 04 is a common bisque range. The right choice depends on the clay body, glaze, application method, and firing schedule. A lower bisque generally leaves the ware more porous; a higher bisque generally makes it stronger and less absorbent. Always start with the clay and glaze manufacturers' recommendations, then test in your own kiln.

Many potters continue using a familiar bisque cone because it has worked in the past. That is a reasonable starting point, but understanding how bisque firing affects absorption, strength, and glaze defects can help you make better choices when changing clay bodies or glazes.

What Bisque Cones 08, 06, and 04 Mean

A pyrometric cone measures heatwork, the combined effect of temperature and time. It is not a single fixed temperature. Also, Cone 06 is much cooler than Cone 6; the zero makes a major difference. For more on interpreting cones, see the related lesson below.

Q&A on Pyrometric Cones

These are tendencies, not guaranteed outcomes. Clay composition, heating rate, soak time, and kiln conditions can change the results.

Choosing a Bisque Temperature for Low-Fire Pottery

Some commercial low-fire systems recommend bisque firing to Cone 04 and glaze firing to Cone 06. In those systems, the hotter bisque can help complete the burnout of organics and other gas-producing materials before the glaze melts. This is not a universal rule: other low-fire clay and glaze combinations use different schedules.

From our studio experience: I have bisque fired some low-fire pieces to Cone 06 and glaze fired them to Cone 06 in the same kiln load, with satisfactory results for the clay and glaze combinations I used. That experience does not mean the same schedule is suitable for every clay body.

Low-fire glazes may be brushed, dipped, poured, or sprayed. The right bisque porosity depends partly on how the glaze is applied and how the glaze slurry is formulated. A less absorbent bisque can require more drying time or a different application technique.

Choosing a Bisque Temperature for Mid-Range and High-Fire Pottery

For stoneware and porcelain that will receive a higher glaze firing, the goal is often to retain enough porosity for reliable glazing while making the bisqueware strong enough to handle. A common starting range is Cone 08 to Cone 06, but some clay bodies and glaze processes perform better with a hotter bisque, such as Cone 04.

When bisque firing is too low for a particular clay body, the ware may remain fragile or absorb glaze water too rapidly. When it is too high, the surface may absorb water slowly, making some glaze applications more difficult. Neither outcome is determined by cone number alone.

Transformation of Ceramic Materials Relative to Temperature

Advantages and Limitations of a Higher Bisque Temperature

A hotter bisque, such as Cone 04, can increase handling strength and allow more of the clay's gas-producing constituents to burn out before glazing. However, the ware may absorb glaze water more slowly, so the glaze mixture, application thickness, or drying time may need adjustment.

Higher bisque firing does not automatically prevent dunting (cracking caused by thermal stress). Dunting also depends on clay composition, piece thickness, kiln loading, and heating and cooling rates.

Advantages and Limitations of a Lower Bisque Temperature

A lower bisque, such as Cone 08 or Cone 010, generally leaves ware more porous and may make some glaze applications easier. However, pieces may be more fragile during handling, and the glaze may build up too thickly if the bisque absorbs water very quickly.

For Raku and other rapid-temperature-change processes, thermal-shock behavior depends heavily on the clay body, its grog content, form, and firing and cooling procedure. Lower bisque porosity by itself is not a reliable predictor of thermal-shock resistance.

Troubleshooting Glaze Absorption and Firing Defects

If glaze remains wet on the bisqueware for an unusually long time, the surface may be too dense for that application method. A slightly lower bisque temperature might help, but first check the clay body, glaze slurry, and application method.

If glaze develops pinholes, blisters, or bloating, incomplete burnout during bisque firing may be one contributor. Other causes include glaze chemistry, excessive glaze thickness, trapped gases, ventilation, and firing schedules. Raising the bisque cone is not a guaranteed cure. Test one variable at a time before changing a production firing schedule.

Pinholes and Pitting: Causes and Solutions

How to Choose Your Bisque Temperature

If your present bisque schedule gives consistent results, there may be no reason to change it. When trying a new clay body or glaze, start with the manufacturers' recommendations. Fire small test pieces at two or three suitable bisque cones, apply the same glaze consistently, and compare drying time, coverage, handling strength, and final fired results.

Use witness cones to check the heatwork actually reached in your kiln, and record the clay, bisque cone, glaze, application method, and firing schedule. That record is more useful than relying on a cone number alone.

Relevant Lakeside Pottery Lessons