A Laser That Doesn’t Burn? The Weird Science of “Cold” UV Engraving

When I tell people our laser doesn’t really “burn” things, they look at me like I’ve invented a new law of physics. But here’s the trick: light comes in different colours, and every colour carries a different amount of energy per particle of light (a photon).

Our xTool F2 Ultra UV uses a 355 nm ultraviolet laser, and each of its photons carries roughly 3.5 electron-volts of energy. That’s about three times more than the photons from an infrared laser at 1064 nm, and it’s in the same ballpark as the energy holding many chemical bonds together.

That matters because a laser can remove material in two very different ways. An infrared laser mostly heats a spot until it melts or vaporises, which is why it can scorch a surface. A UV photon has enough punch to help break molecular bonds directly, so the material can be removed with far less heat spreading to its surroundings. Engineers call this “cold” processing, though the spot isn’t literally cold. The result is crisp edges, tiny details and much less of the browning or melting you get with heat-based marking.

For us in the workshop, that means we can engrave glass, crystal, acrylic and other delicate materials with fine text and sharp lines. It’s also why the same machine can write inside a glass block, which I explain in this post. Next time somebody says “laser equals fire”, you can tell them it’s more like a very, very precise bond-breaking light pen.

Thank you for being with us.

William Alexander Toys