Alum needs to be dissolved in order to be applied to your face. I think dissolving it before applying it to you face makes perfect sense.
Nice. I just tried to make one. The super cheap Walmart olive oil brand for 4 bucks with their Castor Oil from the incontinence section for $2.69 for a 6oz bottle. I need to go grab their glycerin from the band-aid aisle that's in the same bottle for the same price.