A DC controlled unit is ideal but for batteries a 9 Volt set up in series is best. But one 12 volt will change it to a dull bronze color so yes it will work by itself. The titanium will actually start to turn at 9v and it gets more and varied colors on up. 18volts gets up to the purple color. 25 blue 28 lighter blue and so on.
You can use dish washing detergent for mixing in distilled water. Use a glass or plastic jar and scrap piece of titanium for the negative wire if dipping. If not and you are using a touch method you reverse the connections.
Use the search engine and there are lots of other threads on this already posted here with great info.
STR