Here we describe the manufacturing process of planar temperature sensors using plain photocopy paper as a proof of concept. Apparently, the obtained sensor foils are not 100% homogeneous (Fig. 5) due to the structure of the paper yielding uneven distribution of the optical brightener. A possible solution is the use of more sophisticated lifetime based imaging systems. However,more homogeneous sensor foils may also be obtained by employing finer paper types such as e.g. microscopy lens paper. As those papers often do not contain optical brightener a second dye would have to be included in the sensor for referencing.