Alum is still used in industrial paper-making. It acts as a deflocculating agent, separating the pulp fibres.
Those “natural crystal deodorant” sticks you see at places like Whole Foods are generally ammonium alum.
If you get a block of potassium alum, you can rub it all over your wet face after shaving- it stings a little, but generally cuts WAY down on razor burn and irritation.
Just a note, this is the same material as a styptic pencil. Personally I can’t really see rubbing styptic all over my face (I use an astringent liquid aftershave instead), but it’s great for tiny cuts (it does sting, but closes them right up).
If you don’t thrash your face, it may sting a little bit in the places where you’ve angered your skin, but it’ll look and feel better during the day.
I generally rub it on my wet face, and rinse it off a few minutes later.
Alum is my mother’s no-fail cure for a canker sore in the mouth. When I was a kid, she would wet a Q-tip, dip it in the alum, grip my head with amazonian strength while I fought and kicked, dabbed the alum on the canker sore. Yes, it hurts like no other. Yes, it immediately dries up all saliva in that area and if you touch it with your tongue, your tongue goes immediate and completely (it seems at the time) dry. But next day, no matter how big and painful the canker sore was the night before, it was gone and forgotten.
I woke up one morning to a small popping sound in my face followed by a nosebleed that couldn’t be stopped. The source was beyond the soft part of my nose so pinching did nothing but cause the bleeding to back up into my throat. Yup, had to go to the emergency room for a nosebleed. Not the highest priority on the triage list. Eventually, they cauterized the wound with an alum tipped cotton swab. That was easily the second most painful sensation I’ve endured in that part of my face.
You sure it was alum? I thought silver nitrate was always used for chemical cauterization.
Seconded. I’ve been plagued with canker sores all my life and finally tried alum and I haven’t dreaded them since. I moisten a Q-Tip, dab it in some alum and hold it to the sore for five minutes. The sore immediately starts dying and by the next day I hardly know it’s there, though the mostly painless carcass remains for a few days. Still, no more irritated days, pain-filled nights and waiting weeks for the damn things to go away.