In this week's WSJ column, I wrote about how the engineered weaknesses in chocolate bars (the grooves) help break it, & now I have an inbox of cross people telling me they break chocolate by bending towards the groove (pushing down directly on the groove), rather than pushing on the side that doesn’t have a groove. I spent a lot of time drawing diagrams of cracks & fracture zones & it's never occurred to me to push on the groove. How do you do this?
