Dealing with Cold Spots in Glass Annealing
Ever have a piece of glassware—maybe something with a tight neck or a weird flare—that just refuses to heat evenly? It happens. Those tricky shapes create “dead zones” in standard annealing lehrs. You think the whole piece is up to temp, but those cold spots leave behind internal stress. Then, out of nowhere, the glass just snaps. It’s frustrating. To fix this, we don’t just crank up the oven. Instead, we use targeted infrared (IR) lamps to punch heat exactly where it’s needed. It’s about making sure every single inch of the glass hits that annealing point at the same time. Getting the heat where it actually matters The trick is getting a lot of power into a tiny space without cooking the rest of the piece. We use quartz halogen lamps for this. Why? Because they put out short-wave radiation. Instead of just warming up the air around the glass, this energy actually sinks into the surface. By tweaking the wattage and voltage, we can aim the heat right at the spots where the oven’s airflow gets blocked by the shape of the glass. The nitty-gritty on hardware We usually stick with R7s or Sk15 connectors. They’re basically plug-and-play. Your maintenance crew can swap out a burnt-out tube in seconds without having to rip apart the wiring on the rack. One heads-up: keep those quartz tubes spotless. A few fingerprints or a bit of oil might seem like nothing, but they create hotspots that’ll kill the lamp way faster than they should. Finding the sweet spot Here’s the catch. When you add IR arrays to a cooling zone, you’re adding more heat to the system. That puts a bit more pressure on your exhaust. You have to play a balancing act between how hot the lamps are and how fast the conveyor is moving. If you go too aggressive trying to kill a cold spot, you might accidentally create a new hot spot that warps the glass. But once you get the wiring and the timing right, that generic cooling tunnel becomes a precision tool. No more guessing. Just uniform stress relief and glass that actually stays in one piece.