> I am surprised it can cut paper without causing ignition.
As a kid, I had a lot of difficulty trying to ignite paper with lenses under the sun (white notebook paper). I then gave up and used the lenses for cutting instead. So I'm not that surprised.
To this day I wonder what would be the correct set of conditions that would make it easier to combust. I remember trying black paint - that only made the cutting part easier.
I had really no problem using a magnifying glass to burn printer paper as a kid, as long as it was the summer, trying to do that in the winter was for some reason impossible.
As a kid, I had a lot of difficulty trying to ignite paper with lenses under the sun (white notebook paper). I then gave up and used the lenses for cutting instead. So I'm not that surprised.
To this day I wonder what would be the correct set of conditions that would make it easier to combust. I remember trying black paint - that only made the cutting part easier.