Planarizing workpieces, e.g., microelectronic workpieces, can employ a process indicator which is adapted to change an optical property in response to a planarizing condition. This process indicator may, for example, change color in response to reaching a particular temperature or in response to a particular shear force. In this example, the change in color of the process indicator may be correlated with an ongoing operating condition of the planarizing machine, such as excessive downforce, or correlated with an endpoint of the planarizing operation. Incorporating the process indicator in the planarizing medium, as proposed for select applications, can enable relatively simple, real-time collection of information which can be used to control a planarizing operation.