I've been reading this thread with interest and trying to think if I've done anything dumb, I was pretty sure I hadn't but then remembered something today. Before I discovered the pro-gres grinder blade, I used to use vitrex glass cutting blades on my grinder, they gave a very clean cut but didn't last long at all. When they were worn they used to spit red hot bits of molten tile everywhere. On one occasion I was cutting inside the customers garage as it was raining outside, he had a classic motorbike which I'd covered over so it didn't get dusty. The tile I was cutting was a glass border and the hot bits were flying all over the place, I'd done my cut and took it back upstairs only to find it needed a bit more off it, back downstairs I went. I walked back into the garage to find the dust sheet covering the bike was in the early stages of an inferno, obviously caused by the grinder sparks! I quickly whipped it off the bike and dunked it in my wash bucket. If that cut had fitted first time, I wouldn't have been back outside for maybe another half an hour and I have no doubt that the house and it's contents would have burnt to the ground. A lucky escape.