If you’ve ever worked with a glassware annealing kiln, you know the frustration of “dead zones.” It’s a nightmare. You’ve got a piece with a tricky neck, a handle, or a tapered base, and no matter what you do, the heat just doesn’t reach every spot. Standard convection heating is great until it isn’t. The air simply misses the tight corners. That’s where medium-wave infrared lamps come in. They basically bridge the gap. Here is why we go with medium-wave. Short-wave lamps are too aggressive—they can shock the surface of the glass. Long-wave heaters, on the other hand, just don’t dig deep enough. Medium-wave hits that sweet spot. It actually penetrates the glass wall to heat the bulk of the material. This means the core of a thick piece reaches the annealing point without you accidentally cooking the outside. But it’s not just about the type of heat; it’s about where you put it. To kill those cold spots, we don’t just blast the whole kiln. We wrap the lamps around the workpiece. By using quartz tubes with the right wattage, you can aim the heat directly into the “shadows” created by the shape of the glass. It’s a great way to fight off the heat sink effect you get from the kiln’s own supports. Now, there is a catch. High-wattage IR lamps put out a lot of localized heat. That solves your cold spot problem, but it puts a real strain on your control system. If you’re pushing a ton of power into a narrow neck, your PID controllers need to be tuned perfectly. If they’re off, you’ll overshoot the temp and end up stressing the glass all over again. Plus, you’ve got to make sure your wiring can handle the current. If you get voltage drops, your heat will fluctuate, and that’s the last thing you want. The easiest way to handle this? Wire the lamps into zoned circuits. This lets you crank the heat exactly where the dead zones are while letting the other lamps idle where the ambient heat is already doing the job. It’s a simple, drop-in way to finally get a flat thermal profile.