I also tried tawas (Potassium Alum) but the sharp edges only aggravates my already traumatized underarms. The powder form just feels too weird, it's like having sand in my armpits.
Then one day while channel surfing, I chanced upon a DIY Tawas Spray and it's easy as 1-2-3.
Tip: Instead of buying bottled distilled water I make my own by leaving the water out for at least 4 hours. It's not exactly distilled water but this dissipates the oxygen. I think the reason for this is, oxygen makes the spray go bad after some time. This was taught to me by my tita who works in a laboratory. I'm no chemist here, I just follow instructions.
Tip: Tawas is sold in bulk either in Quiapo or Divisoria. I got this ginormous rock in Quiapo for 25 pesos.
First, cut a small chunk of tawas from its big mommy.
Tip: I don't really follow an exact measurement but a little goes a long way. This huge rock has been with me for about two years and up to now mukha pa din syang tawas.
Crush the tawas using the butt or blunt end of the knife.
Tip: Paper makes everything less messy and prevents tawas particles from flying all around.
Pour the crushed tawas in the atomizer bottle.
Tip: Notice how easy it is to pour the tawas.
Shake! Shake! Shake!
Tip:You'll know if you put too much tawas, it won't dissolve and just settle at the bottom. But no biggie, just add more water when there's space.
Voila! Spritz! Spritz! Spritz!
I've been using this home made deodorant for over three years now and so far so good. There are days when it's terribly hot and humid, like last summer, I feel the need to respray but other than that, the "protection" can last up to the wee hours of the morning. My underarms is not "artista" flawless (yet) but the appearance has improved considerably. It also works as a foot spray.