A new process is disclosed for successively measuring the environmental exposure of environmental indicating devices. Environmental indicating devices that may be measured by the new process include devices that have at least one variable region of reflectivity and at least one non-variable region of reflectivity. Upon exposure to chemical, radiation or time-temperature stimuli, the reflectivity of the variable region relative to the reflectivity of the non-variable region is correlated to an incremental change in the environmental exposure of an indicator device based upon a preestablished relationship between the relative reflectivity and the incremental change in the environmental exposure of the device.; The incremental change in the environmental exposure of the indicating device is then correlated to a remaining shelf-life or extent of processing value for a product that undergoes progressive quality changes upon exposure to environmental stimuli. Other information such as the identity of a product and/or of a material comprising the variable region of reflectivity may be read and determined by the correlation process.