These subtly spiritual works, when properly lit, are thought to offer a similar lofty experience that one gets in a place of worship, like a cathedral. Only their refusal to associate with language, or any period in art history, mean they transcend the specificity of religion. But like religious icons, they don't stand up to reproduction. Physically, they rank among the most precious objects in contemporary art. In our age of mass digital reproduction these works are valueless when reproduced as printed copies, but to behold them in the flesh is the closest you will come on earth to having your retinas singed (without gazing into a hot sun).