In Helen of Troy: Goddess, Princess, Whore, for instance, historian Brettany Hughes puts the legendary descriptions of "radiant" Helen in real-world context:
The Mycenaeans’ was a magpie culture. Great sea journeys would be undertaken to bring the finest raw materials and manufactured goods back to the Greek mainland. The more successful a clan-leader was, the more his palace would have glittered—storerooms and tombs would have been stacked with relucent treasure. Cult images were dressed in cloth that had been impregnated with olive oil to give the material a distinctive sheen; privileged mortals too would have worn clothes treated in this way. Those of the highest rank are—for the first time—literally, illustrious. Perhaps this is what the bards meant when they recalled that Helen was ‘radiant’, ‘fair’, ‘shimmering’, ‘golden’....
The ruling classes of the Myacenaeans had access to precious raw materials from across the Eastern Mediterranean—of a calibre and variety never before imagined. And so in marked contrast to the rest of the population, the high-born made sure they gleamed, perpetually, with an artificial lustre. A girl like Helen, sparkling and glinting as she would have done, would have had it reinforced day in and day out, from a very early age, how important, valuable and desirable she was.
The thirteenth-century French vernacular vocabulary included an even broader collection of descriptive terms conveying light-producing and reflecting properties: clere, luisant, polis, blanc, sors, not to mention a constantly varying repertoire of similes to snow, metals, gems, and so on….examples of light imagery and terminology in vernacular literature, from the light reflecting off armor in battle to the gleaming blond tresses and bright complexion of the lady in cansos and romances.
In the Middle Ages, Heller reminds us, "Light was a tangible experience, something that could be purchased by individuals rather than something provided without cessation by anonymous public power companies." As I've noted previously, many glittering objects that seem gaudy under today's electric lights were more mysterious--and, hence, glamorous--in the half light for which they were designed, and in which they represented rare and precious illumination. Nowadays, we create glamour by dimming the lights to add mystery and heighten the specialness of the scene. Once, though, light itself was a special effect. (And even today shiny accessories, though apparently not the Marc Jacobs bag, are generally reserved for evening.)