Check out the blog post:
This is the arc furnace I built with a friend, based mostly on The King of Random's plans. I melted some copper scrap and cast a Cu tile for my element collection. It took about four minutes to completely liquify. The sand is the standard play sand/ground cat litter mix. The white furnace body is a soft alumina fire brick.
I also tried iron. It melted, but I burned myself a bit trying to pour it, so the pour was incomplete.
Although TKOR's design is great, it still has a lot of room for improvement. For example, the furnace body and electrode holders get much too hot to handle through fireproof gloves when I try to melt iron. Check out the video documenting these important improvements here: