Dealing with Cold Spots in Glass Annealing
Ever tried annealing a piece with a narrow neck or a really deep base? It’s a headache. You’ve got your kiln running, but those awkward geometries create “dead zones” where the heat just doesn’t reach. You can’t just hope the air in the kiln does the job—it won’t. That’s why we use targeted IR heating lamps. They basically bridge the gap, making sure the whole piece stays at the right temperature, not just the easy-to-reach parts.
Getting the Heat Right
When you’re working with borosilicate or soda-lime glass, you need some serious punch. High-intensity shortwave radiation is the way to go. We set up the IR lamps in arrays that wrap around the vessel, which lets the heat soak right into the glass rather than just sitting on the surface. But here’s the tricky part: the distance. If the lamp is too close, you’ll fry one spot and risk a thermal shock. Too far? You lose the heat density you need for a proper soak. We use adjustable mounting brackets for this. It lets you tweak the distance on the fly based on how wide your piece is.
The Trade-offs
We stick with quartz-halogen elements because they’re fast. Like, “flip a switch and it’s hot” fast. You aren’t sitting around waiting for a massive heating element to slowly warm up. But there’s a catch. These tubes put out a ton of waste heat. If you cram too many lamps into a small space, your control system is going to struggle when it’s time to cool things down. You’ll feel it. To keep things under control, you’ve got to make sure your fans and venting can actually handle that extra heat load.
No More Shadowed Areas
To really kill off those cold spots, you have to attack from every angle. We layer the lamps at different heights so the radiation hits the “shadowed” areas that usually stay cold. It saves you from that sinking feeling of seeing a piece crack after it leaves the kiln because of internal stress. To keep it precise, we wire everything into a PID controller with a laser pyrometer. It gives you real-time feedback so you don’t accidentally overshoot your target and ruin the work.