From the moment of purchase, pristine objects are subjected to an array of stimuli including wear, impact, heat, light, water and air which alter their tactile and aesthetic properties. Material change is often regarded as ‘damage’ or ‘degradation’, but has potential to be used as a tool to engender emotional engagement to an object and extend product lifetimes. The potential benefits, and complications, associated with material change in the context of designing for the circular economy and other sustainable product service systems is discussed. We present a framework for designers to better understand how materials change with use, and in turn how people respond to materials as they change. Key challenges are identified which must be overcome to use this framework in design practice: people's physical interaction with objects is poorly understood, it is difficult to simulate material change, materials resources for designers do not provide information about material change, and people's responses to aged materials depend on a complex web of interacting factors.