Laser-induced fluorescence (LIF)-based spray vol. and droplet-size measurements rely on assumptions about the evapn. or accumulation of fluorescent tracers during the evapn. of the droplets. The authors study the time-dependent variation of droplet-size and LIF signal intensity of CO2-laser-heated evapg. H2O droplets doped with rhodamine 6G. After an initial decrease of fluorescence intensity by 30% due to temp.-dependent diffusion of O into the droplets, the LIF signal remains const., indicating that the tracers have fully accumulated in the droplet. This evapn.-independent signal can be used as a ref. for Mie-scattering-based droplet surface-area measurements that will allow the sensitive observation of spray evapn. and droplet breakup.