Review (5/5): Really remarkable!
I repeatedly saw alum as a recommendation on shaving sites and shaving tip videos. Having little lose, I gave it a try to combat my razor bumps. The first time I tried this stuff it was AMAZING. I used it before shaving, applying it before the creme, and the shave felt better, smoother, and closer. Afterwards, I had less razor bumps and after a few months they had practically vanished. So the least I can say is that it worked for me.
After losing it while traveling, I shaved without it for a few weeks and did my typical aftershave routine. Bam! Razor bumps. And I agree with other reviews: these things are so dense that as small as it is, it will last you a long time! After a few months, I couldn't even tell it had been used.