It's a massive difference on sash windows. Here's a few pics of my local type of sash window which I restore a lot. The putty had failed on both sides of the glass in this sash so all the glass had to come out, I think it's 21 panes in the top sash. The IR heater softens the putty and it comes out a treat. You can see I'm using a bit of glass wrapped in mirror backing to stop the pane on the other side of the beading from cracking due to heat.
It's a massive difference on sash windows. Here's a few pics of my local type of sash window which I restore a lot. The putty had failed on both sides of the glass in this sash so all the glass had to come out, I think it's 21 panes in the top sash. The IR heater softens the putty and it comes out a treat. You can see I'm using a bit of glass wrapped in mirror backing to stop the pane on the other side of the beading from cracking due to heat.