Kiln Controller: High-Temperature Pottery Automation

A pottery kiln controller automates the complex temperature ramp-soak-cool profiles required for firing ceramics, glass fusing, and heat treatment. Precise control prevents cracking, warping, and incomplete vitrification. This guide covers building an Arduino-based kiln controller capable of managing temperatures up to 1,200°C.

What Is a Kiln Controller?

Ceramic firing follows strict temperature profiles: slow ramp to drive off moisture (room temp to 600°C over 4-6 hours), faster ramp to vitrification temperature (600°C to 1,000-1,200°C), soak at peak temperature, then controlled cooling. Deviating from this profile cracks pottery, wastes glaze, and can damage kiln furniture.

Temperature Requirements for Ceramics

• Bisque firing: 900-1,000°C (first firing to harden clay)
• Glaze firing: 1,000-1,280°C (melts glaze coating)
• Glass fusing: 700-850°C
• Annealing (metal): 300-800°C depending on alloy
• Heat treatment (steel): 750-1,050°C for hardening

Components for High-Temperature Control

• K-type thermocouple (high-temperature rated, 0-1,200°C)
• MAX6675 thermocouple module (₹229)
• Arduino Mega (more memory for complex profiles) or Uno for simple profiles
• SSR 40A or higher (kilns draw 15-30A at 230V)
• SSR heat sink (₹110) — essential for continuous high-current switching
• OLED or LCD display
• Rotary encoder for profile selection

K-Type Thermocouple and MAX6675

The MAX6675 module with K-type thermocouple reads temperatures up to 1,024°C. For kilns firing above 1,024°C, use the MAX31855 module (reads up to 1,350°C) or an analog thermocouple amplifier (AD8495). Place the thermocouple tip in the kiln chamber, routing the wire through a dedicated thermocouple port.

PID Control for Kiln Ramp Profiles

Kiln profiles are defined as segments: each segment has a target temperature and ramp rate (°C/hour). The Arduino steps through segments sequentially, using PID to maintain the ramp rate and soak temperatures.

// Example bisque fire profile
struct Segment { float targetTemp; float rampRate; unsigned long soakMinutes; };
Segment profile[] = {
  {120, 80, 30},    // Ramp to 120°C at 80°C/hr, soak 30min
  {600, 100, 0},    // Ramp to 600°C at 100°C/hr, no soak
  {950, 150, 20},   // Ramp to 950°C at 150°C/hr, soak 20min
  {0, -100, 0}      // Cool at 100°C/hr (kiln off, natural cooling)
};

SSR Switching for High-Power Elements

Kilns draw enormous current — a small pottery kiln runs at 15-30A at 230V AC (3,500-7,000W). Use an SSR rated for at least 40A with proper heat sinking. The SSR heat sink (₹110 on Zbotic) is essential — a 40A SSR at full load dissipates 40W as heat. Without a heat sink, the SSR will overheat and fail.

Recommended Components

Safety for High-Temperature Operation

• Kilns reach 1,000-1,200°C — everything near the kiln gets extremely hot
• Never open a kiln above 200°C — thermal shock cracks ceramics and can shatter kiln shelves explosively
• SSR failure mode is typically short-circuit (always on). Add a backup contactor or thermal fuse on the kiln element circuit.
• Ensure proper ventilation — some glazes release toxic fumes during firing
• The kiln enclosure must be on a non-combustible surface with clearance on all sides