Kiln Firing Schedule

Firing a kiln isn't a single steady ramp to peak temperature — this calculator breaks the climb into four distinct phases because clay behaves differently at different temperature bands. From room temperature (70°F) to 250°F, the schedule runs at half your entered ramp rate to slowly drive off physical water still trapped in the clay body; heating too fast here is a classic cause of exploded greenware. From 250°F to 900°F it climbs at your full ramp rate, then slows again to 60% of that rate through 900–1100°F to ease through quartz inversion — the point near 1063°F where silica crystals abruptly change structure and can crack ware if rushed. Above 1100°F it ramps at full rate to your target peak, which the calculator maps from a simplified cone selector (1 = Cone 06 at 1828°F, 2 = Cone 6 at 2232°F, 3 = Cone 10 at 2345°F), then holds there for your specified soak time.

A kiln-size multiplier (0.85 for small, 1.0 for medium, 1.2 for large) stretches the ramp phases to account for larger kilns heating more slowly. Cooling time is estimated as a flat 1.5x the total ramp time, a common rule of thumb for safe cool-down without thermal shock, not a physics-based simulation of your specific kiln's mass and insulation. The four-phase ramp/cool structure holds regardless of kiln brand, but the exact hours will drift with your kiln's actual insulation, element condition, and elevation, so always cross-check against your kiln manufacturer's schedule and watch pyrometric cones in the actual chamber rather than trusting the clock alone.