7.3 Watt cutting metal

[Benm]

Those IR thermometers aren't very accurate on shiny metal surfaces though, nor on pools of liquid metals. By the time you get over 1000 C or so you'll probably be able to tell rough temperature by the glow color you see.

Magnesium should be interesting as it's auto-ignition temperature can be quite low depeding on form factor. Something like magnesium ribbon or fine shavings can be set on fire around 500 C. I suppose it's possible to set a thin sheet of magnesium on fire when trying to laser-cut it in air. Probably a nicely satisfying thing to watch, but be careful as those fires are hard to put out once blazing.

 

[DashApple]

I remember lighting magnesium ribbon strips with the 60W co2 laser I had , did take a good 20 seconds or so but that was probably due to the poor absorption of the 10.6um light

 

[Benm]

Possibly - it's also quite reflective to visible light, though ribbon will slowly tarnish a bit which normally makes it more difficult to ignite with a flame, but perhaps easier with a (visible) laser.

 

[VirtueViolater]

I've lit mg shavings with a 7w 445