I was doing a rose window over the weekend and I got in a wrestling match with some Spectrum red ruby waterglass and it just about whupped me. I produced scrap on about a quarter of the pieces, having to redo some three times.
To be honest, it wasn't all the glass's fault. I'd been lucky with easy cutting glass before that and I got into bad habits like not doing preliminary cuts on concave parts. I also found out that I just about had to do just one cut and break at a time. Multiple cuts before breaking broke into the other cuts.
Anyway, this window is my third now and I can see the quality of my work improving. Very satisfying. I'm getting closer fits with less grinding.
Michael