Dealing with Cold Spots in Long Glass Tunnel Kilns
Most infrared lamps stop at 1 or 1.5 meters. That’s fine for small projects, but if you’re running oversized glass sheets through a tunnel kiln, you hit a wall. Literally. Those gaps where one lamp ends and the next begins create “cold spots.” When your heat isn’t consistent, your glass suffers. We fix this by building custom infrared units that stretch well past 2 meters, so the heat stays steady across the entire surface. No gaps, no surprises.
The trick to long-form tubes
You can’t just stretch a standard lamp and hope for the best. If you do, the filament will either sag or just burn out. To make a 2-meter tube actually work, we have to get nerdy with the voltage and wattage. We usually move to higher voltage setups or split the internal circuitry into different zones. It’s all about the ohms. We recalculate everything to make sure the power doesn’t spike at the ends, keeping the heat density the same from the first centimeter to the last.
Giving the glass room to breathe
Since these spans are so long, we use heavy-wall quartz glass. It’s tougher and handles the mechanical stress better. But here is the tricky part: heat makes things expand. If you bolt these tubes down too tight, they’ll snap the second they hit operating temperature. It’s a loud, expensive mistake. We use specialized connectors and mounting brackets that let the quartz “breathe” and shift slightly while staying perfectly centered.
The honest trade-offs
Here is the reality: longer lamps move a massive amount of heat, but they’re fragile. A tube over 2 meters is way more sensitive to vibrations or a stray bump than a short one. You need a rock-solid structural frame for your kiln. And don’t forget your power supply. These arrays pull a lot of inrush current. If your wiring isn’t beefy enough to handle the load, you’ll get voltage drops. And when the voltage drops, your annealing becomes uneven, and you’re right back to square one.