| abstract |
According to one aspect of the present invention there is provided a coating material comprising: a functional coating component; and a fluorescent additive component whose fluorescence is substantially unquenched by the coating component, the fluorescent additive component having a peak fluorescence emission under excitation by visible or infrared light, the wavelength of that peak fluorescence emission being greater than 500 nm and lying outside the principal fluorescence absorption and emission wavelengths of the coating component. |