Figure 2. Use of water as a self-erasable fluorescent writing ink.

(a) Photographs of hand written images on a PE1 coated fluorescent paper under illumination at 365 nm over a period of 4 h. A secondary plot of the corresponding changes in the fluorescence spectra is shown in the middle. (b) Changes in the fluorescence colour of paper upon repeated cycles of writing with water and erasing with hot air. (c) Changes in the photoluminescence colour of paper upon exposure to different relative humidity.