Kiln building
For recycling / remelting glass
Temperatures 2200 F – 2350 F (1204 C – 1288 C).
Need a S type thermocouple (up to 1450 C). ebay, $25
Glass blowing temperatures
“The transformation of raw materials into glass takes place around 1,320 °C (2,400 °F); the glass emits enough heat to appear almost white hot. The glass is then left to “fine out” (allowing the bubbles to rise out of the mass), and then the working temperature is reduced in the furnace to around 1,090 °C (2,000 °F).”
Refractories
Ceramic Fiber Board, good to 2600 F
CeraMark Ceramic Board, 2300 F 2″, 16 sq ft / $400; 2600℉ 2″ 16 sq ft $584
Simon Store Ceramic Fiber Board, 2300 F 5.4 sq ft / $140; 2300F, Ultra Strength board; 2600 F 5.4 sq ft / $126
Sources for Kanthal A1 wire (FeCrAl wire)
https://kilnparts.com, 15 gauge, $0.56/ft
ebay, 15 gauge, 66 ft / $52.; 16 gauge, 50 ft / $22
Kanthal A1, max temp 1400C
Kanthal A1 Wire Specs
| Wire Gauge (B&S) | Ohms/Foot | Ohms/Inch | Diameter – Inches |
lbs/1000 Feet |
| 13 | .1673 | .01394 | .072 (1.83 mm) | 12.6 |
| 14 | .2123 | 0.0177 | .064 (1.63 mm | 10 |
| 15 | .2639 | 0.0292 | .057 (1.45 mm) | 7.93 |
| 16 | .3312 | 0.0276 | .0508 (1.3 mm) | 6.28 |
| 20 | .8661 | .07215 | .032 (0.81 mm) | 2.49 |
Kanthal D, max temp 1300C
ebay, 1-5mm: 2.5mm, 10m $110
Silicon Carbide heating elements
Made with a hot area (alpha-silicon carbide, sintered at 2100-2300C) and cold areas (beta-silicon carbide, sintered at 1700C) with lower resistance, and thus less heating. Connected with aluminum braid clamped to the ends. Ends are often coated with aluminum (sprayed on). Sintering can be aided by added a little carbon (powder or cellulose binder) and boron carbide, at 1-2% each. Sintering is typically done in a graphite furnace (with inert atmosphere).
Silicon carbide powder used as abrasive can be used to form elements. (see Shake the Future kiln building video). Heats up in a microwave–this is the heating element in microwave kilns.
Resistance varies with temperature.
Can be used to 1650C.
References
Vacuum Kiln
Estimate 2″ – 3″ insulation, reduces kiln size by 4″-6″ in each dimension.
Vacuum chamber out of sheet steel
20″x20″x20″ (15″x15″x15″ interior) — 12 gauge mild steel hot rolled, 20″x60″ and 20″x40″ ($185), door of 21″x21″x3/16″ ($71). Bike inner tube for a gasket. Add 1″ tubing diagonal to reinforce sides, 28″ x 6, $42. Weld sides to make open box, weld on 1″ tubing for reinforcement. Weld hinges to door.
Ceramic fiber board, 2″x19.7″x39.4″ x 3 = $375.
Fire brick, soft insulating, (2.5″x4.5″x9″) 2×4 per side x 6 sides = 48 x $5 (2300F) or $6.50 (2600F) $200 – $275 + 1/2″ ceramic board (2300F), 19.7″x39.4″ x 3 = $240
24″x24″x18″ vacuum kiln (18″x18″12″ interior)
vacuum oven, with 2″ insulation interior 5″x8″x5″