The high E string on my little guitar was sacrificed Wednesday night for my first attempt at hot wire ice cutting. The strings needed changing anyway as they have miraculously survived more than 2.5 years of frequent travel without a case. With an old cell phone charger (5.7V, 800mA) as a power source, the wire warmed up enough (maybe 150°F) to easily cut through foam peanuts, but it did nothing to a block of ice.
More electrons were required, so I dug around until I found a bigger power supply (18V, 1111mA) from an old DSL modem. With that much juice, the wire became red hot in less than a second! I gently cut through the corner of a 10 pound ice block and noticed that the wire went dark where it came in contact with the ice. After penetrating about an inch, the wire broke. It seems that it became extremely fragile at the edge of the ice where there was a high temperature differential. After it broke, I noticed that the ice had re-frozen behind the wire, leaving the wire trapped within the ice.
Encouraged, I glanced around for some sturdier wire and decided to try some 1/16" picture hanging wire. This turned out to be a poor choice as I stupidly failed to measure the wire's resistance prior to hooking up the power supply. It didn't heat up at all, and the power supply completely stopped working. Oops. I then discovered that the wire had no measurable resistance, so I had probably blown a non-serviceable fuse in the power supply by creating a short circuit.
At the office the next day, I happened upon Noel throwing out a 15V 1.2A power supply with a damaged DC cable. Perfect! I also picked up some nichrome wire and a couple sizes of steel wire at a hobby store. Hopefully I'll be able to come up with an effective but less fragile combination of power and wire.