When I was renovating my last house I tore down most of the kitchen and stripped all the wiring out of the ceiling. For a long time the only light we had in there was a fluorescent strip light that I had plugged in and leaning against the wall.
It gave off a harsh headache enducing white light. It was good that the only cooking facilities were via microwave. You wouldn't want to be in that kitchen too long.
But I used to refer to that light as my Dan Flavin. (I also used to refer to the pile of bricks I had stacked outside the back door, ready for that never-to-be-finished garden wall as my Carl Andre but that's another story).
At the Hayward Gallery there's a Flavin retrospective. It's hard to explain how good it is. Flavin's idea to use commercial fittings as a light environment was simple enough and if you see the works on paper or crammed into the corner of a mixed room at a major gallery space it's easy to dismiss them as mere minimalist pretence. But in situ, properly spaced and carefully curated Flavin's precise arrangements of standard strip lights turn the works into a funhouse of shadows, shapes and subtly vibrating colour.
Flavin was famously dismissive of attempts to define his art. "It is what it is. And it ain't nothing else". But he was protective of his ideas, creating complicated systems of certification and restoration contracts ensuring that the seemingly simplistic and easily constructed works that he sold were not duplicated without his consent.
Indeed much of the work on show here has been created specifically for this show based on Flavin's documentation. Most of it will be dismantled and disposed of rather than being shipped to the next venue. What you are physically looking at could well be worth less than the fittings in the foyer coffee shop, but what you experience is where Flavin's greatness rests.