170-pound Silicon Carbide Electric Glass Furnace | Instructional Video
Instructional video for the construction of a 170-pound Silicon Carbide Electric Glass Furnace.
- 240 minutes
- ©Mark Lauckner
- Available as: 2 DVD Set $45 post-paid
- Online Viewing coming soon
Have a look at the sample clips from the video and the photos below. The door bricks and fiber panels are all painted flat black. This provides a few functions. Firstly, a crust which prevents airborne fibers, secondly, a bit of mechanical protection against erosion of the fiber exposed by the expanded mesh. Thirdly, the color and texture of the paint aids in the ability of accumulated heat to radiate from the insulation’s outer surface. When I place my hand on the furnace sides, the temperature is just slightly warmer than room temp. Compare this to furnaces with shiny sheet metal skins that you can’t even touch! Notice the photo of the hearth brick. It is a hard firebrick “split” and is positioned right in front of the curved trough brick casting, and directly under the door. Ladle gathers often result in a thin thread of glass following the gather out of the furnace. (There is no flame in electric furnaces to burn off this thread.) The tight closure of the door can be affected by an accumulation of hardened stringers in this location. If the door is open even a wee bit, there can be convection cooling by escaping hot air. These “consumable” bricks are just over $1.00 each and can easily be swapped while the furnace is hot, as required. There is 1/2″ of sand sitting on the fiber insulation beneath the region where the cast curved trough brick meets the front brick, in case there is any glass seeping down between them. A small bed of sand is really useful for the removal of any gummy parts like this, and can also easily be replenished while the furnace is hot.
The total cost to build this in 2003 was $4000, including controller and crucible. Also below is a picture of the furnace at operating temperature. Note the build-up of stringers below the yoke bar. These are cleaned off regularly along with the gunk on the sill brick.
As of 2019 I have replaced the crucible twice and again a 3rd time in the summer of 2020. I have melted a little over 60,000 pounds per crucible, well over 300 charges per crucible. Because of the hard refractory investment around the crucible, I continue to use it for at least 150 charges after it starts to show signs of cracking.
Parts list is provided with the DVD set, PDF version is available here.