Novice: The alchemist has become very adept at fighting with his grenades. He receives the Accuracy (Grenades) focus if he doesn't already have it and adds his Perception to damage rolls with grenades.
Journeyman: While delving into this unpredictable science, the alchemist has most likely experienced is fair share of explosions. When subject to the Kaboom! stunt, the alchemist only takes half the amount of damage (rounded down).
Master: The alchemist knows the recipes for his grenades like the back of his hand and can make brew a new one at a much faster rate. Once per encounter, the alchemist can use an Activate action to make a TN 13 Intelligence (Brewing) test. The alchemist creates one kind of grenade they can normally make on the spot on a successful result.