A charge director injection system includes a charge director tank, a liquid toner tank, a charge director pump to pump charge director from the charge director tank into the liquid toner tank, and a control system configured to measure a change in charge density per amount of charge director injected into the liquid toner tank, and create a charge profile indicating a relationship between amount of charge director injected into the liquid toner and change in charge density of the liquid toner within the liquid toner tank.