"How can colours be marked on stainless steel?"
Annealing colours are superficial colourations on stainless steel, resulting from heat. The ability to generate these colours with a laser has been possible for a while now, and is always being scientifically investigated and improved upon. Today, it is easy to mark exact colours again and again, with perfect results every time. This is done with MOPA lasers, which are powerful and fast, but also give you the option to select your pulse durations. The laser parameters can be tuned very precisely, so that marking your desired colours can be quick, easy and trouble-free - and you'll always have perfect, high-quality results.
A large focal length (and large spot diameter) along with small filling line distances mean that the annealing colours can all be generated directly in focus. Thanks to these small filling line distances, colour marking by tempering takes a somewhat long time.