Back in the Kodachromagnon Age, when film was both alpha male and alpha female, transparencies were born as slides, but could transform — by the mystical power of Kodak Labs — into framable prints whose faces were either glossy or matte.
Without intending to, some anonymous, incompetent, color-blind photo lab worker gave me the key to understanding the eternal (since 1839 or 1840, anyway) complaint:
Space, Time, and Raspberries 