The bar is clamped in a metal vise, so the vise is very slightly heated and that side of the bar is much cooler.
Taken using the Topdon Android attachment.
Once I used an oscillating multi-tool to saw a 1x2 wall stud that had water damage. It hit a nail and sparked a bit, then started to smoke, and then ignited the sawdust with a little flame shooting out from the cut.