Why glass cracks in annealing

Thu, 23 Jul 2026 12:43:01 +0800

Ever had a piece of glass just… snap? It’s a nightmare. Usually, it happens during annealing because the temperature is jumping around too much. If the outside of the glass gets hot while the core is still cold, the tension builds up until the material just gives way. It happens a lot with infrared (IR) heaters, especially when the control isn’t quite right or the voltage is off. The voltage trap I see this all the time: engineers trying to force a heater to work on a power grid it wasn’t built for. If you plug a 110V lamp into a 480V or 575V line without a transformer, you’re going to fry that filament instantly. Poof. Gone. But going the other way is just as bad. Under-powering a lamp means your heat isn’t spreading evenly. To keep your glass from cracking, you need a steady, predictable flow of heat. That’s why we customize our voltages (110V/480V/575V) to match your setup. When the wattage bounces around, your annealing curve shifts, and that’s when the glass breaks. Dealing with heat density Shortwave IR is great because it digs deep into the material. But if it’s too intense in one spot, you get “hot spots.” We spend a lot of time spec-ing our lamps to make sure the power is balanced across the whole tube. Now, high-wattage tubes move a ton of heat, but they put a real strain on your cooling system. If your machine can’t get rid of that ambient heat, the housing can actually warp. Once that happens, your focal point shifts, and suddenly you’ve got localized overheating. Not a good look. The trade-off Here’s the thing: there’s no such thing as “set it and forget it” with heating. If you crank up the voltage to speed up your cycle, you’re cutting into the time the glass needs to stabilize. You’re basically trading safety for speed. To keep things from shattering, I always recommend ramping the power in stages. And for heaven’s sake, make sure your lamp voltage matches your local grid exactly. It keeps the heat climb smooth and linear, which means no internal stress and no broken glass.

Cracks on Infrared Heating Tubes

Why glass cracks in annealing