My staff and I conduct homeowner workshops in conjunction with the Preservation Alliance of Philadelphia 8 evenings a year. When the topic turns to window repair, we always know that there are going to be a dozen questions concerning the removal of old, hardened putty. I know that there are a number of techniques including steam, chemical, heat gun (careful!) Fein multi-master reciprocating blades, and everyones favorite, slowly picking away with a cheap chisel and a utility knife. About a dozen years ago I stumbled upon a 50's era electric putty softener at an antique tool auction. I actually wasn't certain what it was and the list of auction lots wasn't that helpful. It is an "L" shaped tool with a heating coil tucked into a "V" shaped recess around 2 sides. When it was plugged in (no switch) the coils glowed red. You can set it directly on the glass and slide it up against the hardened putty. Within 30 seconds the putty was as soft as clay and easy to scrape away. I was hooked. Since then I've purchased a modern version from CR Laurence which is a bit larger and heats on 3 sides, and I've used it frequently. I'm curious to know if anyone else has any secret tools or techniques for removing old glazing. Incidentally, the putty softener greatly lessens the chance of differentially heating the glass and cracking it, but it doesn't eliminate it. Used with care it can make a difficult task much easier to take.