There are two (common, at least) types of alum -- potassium and ammonium, but they are not each specifically for one use or the other. Both types are sold as deodorant and can often be seen side-by-side on store shelves.
Originally Posted by elsmooth
Most (but perhaps not all) places that sell alum blocks for the purpose of shaving sell the potassium variation, at least in my limited experience. I suspect little difference in practice but have heard that the ammonium version stings a bit more. Some may see this as a disadvantage and others may see it as evidence that it is more effective than the potassium alum.
The alum block I use for shaving is potassium alum, called "Thai Crystal", and is sold as a deodorant. Its packaging (as mentioned earlier by luvmysuper) makes it ideal. It closes up tightly and when in use you can hold on to the plastic case instead of the block itself.
Last edited by Bertilak; 07-01-2010 at 02:02 PM.
Somebody's nuts. I don't know whether it's me or them, but somebody is definitely nuts. I just wished I knew, so I'd know, you know?