By 1963 Flavin’s work consisted of simple, unadorned, commercially produced fluorescent tubes. He preferred fluorescent light because it softened and suppressed shadows in an even radiance, thereby producing a different perception of spatial volume. In his light installations, which rely totally on the interior architectural spaces of the gallery, the relationship of object and environment becomes crucial. Flavin summarized his experiments with fluorescent light:
In time, I came to these conclusions about what I had found with fluorescent light, and about what might be accomplished plastically: now the entire interior spatial container and its components wall, floor, ceiling could support a strip of light but would not restrict its act of light except to enfold it … Realizing this, I knew that the actual space of a room could be disrupted and played with by careful, thorough composition of the illuminating equipment. The fluorescent light tube ceases to function as art the moment it is turned off. It is the light, not the tube that occupies the space and is the material of art. And the meaning of Flavin’s work is clearly dependent on its being placed within an art context, such as an artist’s studio or a gallery.