On the glass line, drying after external spray is where you either make yield or watch it disappear. If the heat isn’t even, thermal stress builds and bottles start to crack. If convection takes over, the coating cures unevenly and optical quality goes sideways. We built our external spray drying modules around one hard requirement: keep temperature uniform across the bottle surface, with no hot spots and no cold zones. What actually matters under the hood We run medium-wave infrared emitters in quartz envelopes—fast response, predictable output. The emitters are laid out so power density maps to the bottle profile, and every square centimeter gets the same energy flux. Temperature control holds ±2°C across the drying window, and the system keeps up with line speeds from 300 to 2,000 bottles per minute. Power density is tuned to the coating’s emissivity and the mass of the glass, so you don’t get runaway heating that drives warpage. Here’s why that matters. Uniform heating keeps those sharp thermal gradients from forming—the kind that cause fractures during tempering and bending, and the kind that wreck dimensional stability while the coating cures. The payoff is fewer rejects from stress fractures, optical distortion, and surface defects. Plus, the fast ramp-up shortens the drying dwell, so you keep throughput without having to crank the temperature. Energy use drops because the energy goes into the glass where it’s needed, not into heating air and the conveyor hardware. A few practical notes for install and upkeep Alignment has to be dead-on to the bottle path, and the power zone needs to stay clean and dry. If it’s off, you get shadowing—and that shows up as curing variation. Commissioning is short, but you’ll want to dial the emissivity settings for different glass colors and coating thicknesses. Once it’s set, the module stays honest with routine lamp inspection and reflector cleaning. That’s it—keep those two items in check and the performance stays repeatable.