Just wanted to pass this on after seeing some relatively expensive prices for alum blocks. I was at Whole Foods the other day browsing the shaving section and they didn't really have much I wanted, including an alum block. So I asked the guy standing there offering to help if they sold alum. He said no. But I went ahead and looked around anyway and found some. Not in shaving, not in Asian cuisine, but in the deodorant section. Apparently alum is one of the key ingredients in deodorant and for the close-to-nature folks they had pure little cubes of alum, about 2"x2"x2" with rounded edges. I think it was around $2.25 for the cube.
Works like a charm and I don't see it dissapearing very soon. I actually like the size of it because it doesn't take up too much precious counter space and it fits along the nooks in my neck nicely.
Other local natural grocery type stores (Sprouts, Natural Grocers, etc.) may have them as well, just don't forget to check the deodorant section.
Spencer