Writes Viola: "Sodium Vapor was recorded over a period of several weeks in the hours between one and five in the morning on the streets of an industrial area in lower Manhattan. The title derives from an interest in the particular qualities of sodium vapor street lighting — its characteristic color temperature, the shadows it casts, and the eerie quality it seems to impart to the objects it illuminates. The essence of the work is the spell which the hour has over the physical spaces of the streets in the early morning. There is always the unseen presence of the large number of people surrounding you, most of them sleeping; the camera is awake in their dreamtime. The recording of these locations in the middle of the night rather than in daylight represents a transformation — like figure/ground reversal — of these physical spaces from the familiar thoughts and activities of the day to the nighttime shadows of emptiness and obscurity."