The temperature profile over time of gypsum boards is monitored as the boards harden, to facilitate effective curing of the boards prior to removing excess water therein in an industrial dryer. A substrate is moved by a curing conveyor beneath a gypsum slurry mixer, and the mixer pours slurry onto the substrate. Just prior to the substrate passing under the mixer, an operator places a temperature monitor onto the substrate. The temperature monitor includes a temperature sensor and a microprocessor that receives and stores the signal from the temperature sensor. The temperature monitor is configured such that the height of the sensor is equal to one-half the height of the hardening boards. The slurry that has poured onto the monitor hardens into a test board, and when the test board arrives at the end of the curing conveyor, an operator breaks open the test board, removes the monitor, and connects the microprocessor in the monitor to a computer via a serial port cable. The computer outputs a temperature profile as recorded by the monitor, with the temperature profile being representative of the efficacy of the curing of the boards in the particular batch of boards that were poured with the test board.