For classic antique pane windows,
I never figured out anything that worked well enough at softening putty 
to be worth the trouble.
And I have changed at least 100 panes of glass in old windows in my time.
  Just dig in

  A "nooker knife" or window chisel is good
or just a regular chisel (maybe not your favorite chisel) and care.

  You are going to break them now and again. Comes with the territory.
Regular old school window glass though, just cut you a new pane.
Cutting glass is part of the antique life.
  If I had you here for even a few minutes, you'd be doing it too.

  Cool news about window and stained glass work.
  Right now, for the first time in my life, (and probably not for long 
as these things go),
  glass cutters are available from China.... heroically cheap!

   Usually when a new product hits the market they offer it for 
practically nothing to see if it sells at all.
  It it doesn't sell they quit making them and if it does sell they 
quadruple the price, sometimes more.
           I bought a whole sack of them.   :)

Here are my regular setting window tools.
Homemade window hammer. You slide it along the pane of glass to drive in 
the points that secure your glass.  A driver I made up, to hold the 
point in place for driving.
  My points box and my window chisel.
  These have served me very well for a long time

  http://users.snowcrest.net/kitty/sgrandstaff/images/house/windowstuff.jpg

I also have an embarrassing number of putty and pallet knives lol
  yours Scott

-- 
*******************************
    Scott Grandstaff
    Box 409 Happy Camp, Ca  96039
    scottg@s...
    http://www.snowcrest.net/kitty/sgrandstaff/
    http://www.snowcrest.net/kitty/hpages/index.html