I recently ordered a shave kit from Bespoke Post and it included something I had never used before — a so-called “alum block.” The actual item was Gentleman Jon Alum Block .
To start, as a fan of design, I really like the tough guy logo.
The block itself looks like some kind of crystal rectangle. The product claims to be 100% potassium alum and is made in China. I try to avoid products made in China whenever possible. (Am I being unfair?)
I already use potassium chloride crystal cubes, also known as KCl, in my water softener, and have looked a bit into KCl as, among other things, a source of beta radiation.