If you really want to see sparks, get a blast match!
I was showing it to someone last night about 12:05am and I was using it on the cement with embeded stones.....I pushed the thing down and the sparks kept burning for over 10-15 seconds!!!!
They just sat there sparking and glowing while the person I was showing it to just stared. <img src="/images/graemlins/grin.gif" alt="" />