Low Mass Glass Kiln



  • Large hearth: 3x6 feet
  • Operable to 1800F+ (for casting)
  • Limited power supply: 80 Amps at 240 VAC, or about 19kW
  • Affordable

Design Overview

  • 3x6 foot hearth shifts design from clamshell to top hat to provide better access
  • Top and bottom elements for more even heat distribution
  • Bottom elements imply a high thermal conductivity hearth
  • Ceramic fiber insulation to reduce lid weight and lower power consumption

Design Details

  • Heating elements all inserted from a detachable top
  • Kanthal AF elements, 11 AWG, on 1" OD mullite tubes
  • 3 Ohms total resistance yields 18.4 kW
  • Fiber insulation implies a floating hearth
  • Recrystallized silicon carbide tiles for hearth (2x3 x 18x18")
  • Individually adjustable mullite hearth support posts (10)
  • 2300F rated end-cut ceramic fiber insulation modules, 6" thick
  • Gold coated quartz viewport windows
  • SG-70 composite panels support internal machined ceramic parts
  • RA330 alloy internal metal parts
  • Mild steel frame with expanded steel mesh tension panels
  • Lid lift mechanism: 2-ton screw operated lift jacks
  • 6 top vents under computerized control
  • Watlow CLS 208 ramping controller with 50A PWM solid state relays
  • Thermal profile equalized via element positioning and resistance 

Kiln Design

Initial CAD

Finished Kiln with viewports



Hearth frame skeleton, with silicon carbide tiles on mullite posts

Hearth supports

Nickel Plated Frame



Insulated hearth bed, with 2 hearth tiles


With hearth elements

Sub-hearth detail - heating elements, fiber, supports, and hearth posts 

Fiber wall modules and silicon carbide hearth


Insulation dance

Top Elements - Kanthal on mullite tubing

Element support hooks: RA330 versus carbide router bit


Watlow CLS208 controller and thermal cutoff




50A SSR switches & main power cutoff relays

Control Station 

Power Busses

As Dr. Frankenstein imagined them

As Igor deployed them

Ceiling Vents

Threaded rod tails


Thermal Simulation

1505F - 1509F

2F variation

Mechanical Simulation

0.01" Deflection of frame when fully loaded

Final Assembly/First Firing

Hearth rolled out

First Glass - even heat at 1400F