Art conservation uses Ultra-violet lighting in a similar way that a detective uses a black light to inspect a crime scene. Awash with the electromagnetic radiation, i.e. light in the form of wavelengths, the painting's secrets are revealed; artist materials fluoresce distinct colours in the visible spectrum depending on the age and type of material present. A conservator is able to approximate the age of a painting (e.g. the milky green-yellow glow of varnish intensifies with time) and discern what is original, artist applied material versus those subsequently added to the painting, such as a restorer or conservator's touch.