Fixing Those Annoying Cold Spots in Glassware Annealing
If you’ve ever worked with complex glass—think weirdly shaped flasks or custom lab gear—you know the struggle. You put everything in the kiln, you wait, and then you find a “dead zone.” It’s that one stubborn cold spot where the glass geometry just blocks the heat. The result? Internal stress. And we all know how that ends: the glass shatters. It’s frustrating, and it’s a waste of time. To stop this from happening, we’ve started using shortwave infrared (IR) lamps as a kind of “backup” heat. Getting the heat where it actually needs to go Most kilns just heat the air. But air is slow. IR lamps are different because they hit the glass directly. By tucking these emitters around the vessel, we can push heat right into those recessed nooks and crannies that a standard kiln simply can’t reach. We aren’t trying to heat the whole room; we’re just filling in the gaps. We use high-power density lamps in a small package so the glass hits that annealing point evenly across the board. The trade-offs (because there’s always a catch) We usually go with quartz-halogen tubes. They’re great because shortwave light sinks into the glass way faster than longwave options. But you have to be smart about the wattage. If you go too heavy, you’ll clear those dead zones quickly, but you’ll put a lot of strain on your power supply and cooling fans. Plus, if you just blast the heat without cycling it properly, you might end up with “hot spots.” That’s just swapping one problem for another. Setting it up We use standard industrial connectors, so these are pretty much drop-in replacements. The best part is wiring them into your existing kiln control loop. That way, the support heaters only kick in when the glass hits the critical temperature zone. It saves a lot of electricity. One quick tip: keep an eye on your shielding. If those quartz tubes get hit by debris or chemical splashes, the filament will burn out way too soon. Keep them clean, and they’ll keep working.