I have a piece of glass out of an old termo-pane window that I would like to cut, but I have found that when you try to cut old glass with a glass cutting tool that you have a hard time getting it to cut(or break apart) with a straight edge, I have tried scoring both sides and that is no help, I would hate to have to take it to a glass cutter because this is something I would like to learn how to do . Does anyone have any ideas? The glass is about 30 yrs. old.

Have you cleaned the glass? I have found that with old glass the most important thing is that it be very clean at the cut line. I use 00 steel wool with Goof-Off first and then a glass cleaner. Also make sure that your cutter is oiled at all times. Hold the cutter at 90 degrees to the glass and make one single pass from start to finish. Never try to re-cut the same line. Breaking within seconds after the cut is very important. When you score your glass you are causing the molecules in the class to line up along the score so breaking as soon after is needed. Hope this helps.

It also breaks better is it's warm.