This looks like a cool little thing to make if you ever need to cut up some foam. As is so often the case, I saw this video on some POS freebooting Facebook page first, but this appears to be the original.
“Do all appropriate safety things” (how’s that for a disclaimer?)
Here’s a nice looking, less temporary build…
I like that! (Looks lots cheaper than the one I bought, that’s for sure.) 
Very cool
Kinda interesting because 9v batteries have relatively high internal resistance (they’re actually 6 tiny 1.5v cylinders mashed together) so you’re going to limit the current to levels that probably won’t make anything but the wire irretrievably hot. (I once accidentally shorted some AAs and melted part of the plastic case they were in, also melted a connecting wire’s insulation.)
I once was carrying several 9v in my chest pocket. I stopped when there was a loud pop and two of them were very bulged.
You can buy ni-chrome wire on Amazon instead of using the stainless wire and it will last longer with less thermal deflection over time.
I rewound my kiln elements with NiChrome, a good high temperature alloy.
This is my version:
I use stainless steel wire. It seems to work well. Seems sturdier than nichrome but I haven’t used that enough to know how long it lasts.
we built a really crude one about 8+ years ago. Way better than using a saw. No snow to clean up.
https://goo.gl/photos/jF8VuDfnRoABw7ZD6
so cool wish I had a reason to build one however I don’t work with foam as its not animal safe 
So… How does this smell?
Toxic. Very toxic.
Literally the same as burning plastic does. Really nasty.
What voltage do you have for that one? 12v?
Yeah I use <12V for that one. I have cut with some longer lengths of wire which required a 24V supply to get to temperature.
