In general, it's much more difficult with white people. It's not racist, people of African descent just have a better gene for scaring. It's why most scaring as decoration started in Africa, and Europeans turned to ink. However, there are several ways to encourage a good scar on white skin.
Ash or charcoal is one, it encourages infection, which is really what you're going for. The infection makes a better scar. If you don't want a huge painful, swollen, pussy cut, lemon juice mixed with salt, hydrogen peroxide, and constant breaking open the scarb also helps. Not peeling or picking, stretching the skin tight and making the top break. Beyond that, jsut making sure the initial cut is 1/8th to 1/4 an inch deep is a major help. Anything 1/8th or less is only semi-perm to nothing. Deeper you get better results.
I'm guessing with mine, it was just hard to press the scalpel as deep as they could in the couple of small lines without pressing too hard. Everything except fo those couple of small lines at the top of the hammer scarred very well.
And that's your daily lesson from your friendly neighborhood modern primitive. Next week, tune in for hook pulls and suspension! ;D