Fugitive pigments are impermanent pigments that lighten, darken, or otherwise change in appearance or physicality over time when exposed to environmental conditions, such as light, temperature, humidity, or pollution. Fugitive pigments are present in types of paint, markers, inks etc., which are used for temporary applications. Fugitive inks which washed away when soaked in water were sometimes used deliberately to prevent postage stamps being removed from envelopes by soaking, and reused.