Getting Glass Tempering Right After Screen Printing
If you’ve ever run glass tubes through a screen printing line, you know the headache. You’re stuck in a tug-of-war. You need enough heat to cure the ink and get the glass tempered so it doesn’t snap, but if you push it too hard? Your patterns bleed and the glass warps. It’s a nightmare. We’ve found that the secret is using short-wave IR sealing lamps to hit that narrow window where everything just works. The battle with heat and shock The goal is to get the tempering done without ruining the art. We use high-density quartz halogen lamps because they don’t mess around. Think about a standard convection oven—it heats the air, which then heats the glass. That’s too slow. These lamps hit the glass surface directly. You can go from room temperature to tempering heat in a few seconds. But you have to be careful with your wattage. If you go too hot, those crisp ink edges start to blur. Too cold, and you’ve got residual stress in the glass that’ll cause it to shatter the moment someone touches it later. We spend a lot of time tuning the lamp placement so the heat hits the tube evenly all the way around. The trade-offs you should know about We stick with quartz envelopes because they can handle the brutal heat needed for sealing. We also use the short-wave spectrum because it actually sinks into the glass rather than just bouncing off the surface. Now, there’s a catch. High-wattage lamps get the job done fast—which is great for your throughput—but they’re thirsty for power and they throw off a ton of heat. If your cooling fans aren’t up to the task, your connectors are going to oxidize and burn out. It’s a frustrating way to kill a machine. Making it work on the shop floor To get a clean finish, you can’t just flip a switch. You have to dial in your belt speed against the lamp intensity. Here is what we suggest: use a staged approach. Start with a pre-heat zone to steady the ink, then hit it with a high-intensity sealing zone for the actual tempering. It stops the glass from “shocking,” which is usually why patterns get distorted. And a pro tip: use high-temp leads for your wiring. Otherwise, the insulation near the lamp heads will just melt right off.