Prerequisites: Alchemist 8.
When you create a bomb, you can choose to render the bomb and its explosion invisible. The bomb itself remains visible until thrown. Your target is denied its Dexterity bonus to AC against an invisible bomb, though you do not gain the +2 attack bonus that invisible creatures typically gain unless you yourself are also invisible. In addition, creatures struck by an invisible bomb or within its blast radius suffer a -2 penalty to Reflex saves against the bomb. Creatures able to see invisible objects or creatures treat an invisible bomb as a normal bomb, as do creatures with uncanny dodge, Greater Blind-Fight, or, if you are within 30 feet, Improved Blind-Fight.