Abstract: A detection system for measuring a dry time of a printing composition used by a printing device is disclosed. An embodiment of the detection system includes a source, a sensor, and a controller. The source is configured to transmit a first light signal toward a quantity of printing composition deposited on a print medium. A sensor is configured to detect a second light signal reflected by the printing composition in response to illumination by the first light signal, the second light signal having a magnitude that decreases to a substantially constant value as the printing composition dries over a period of time. The sensor is also configured to convert the second light signal into an electrical signal having a value proportional to the magnitude of the second light signal. The controller is coupled to the sensor and configured to receive the electrical signal from the sensor over the period of time the printing composition dries.