While I'd agree the dish soap idea was not something I'd ever recommend, I think Nolan should experiment in whatever way he'd like. Everyone is drawn to use film for different reasons, often looking for different results. There is an orthodoxy which crops up, here, on a regular basis. There is no single right way... no single right camera... no single right developer...no single right photograph. The beauty in our choice to use film/darkroom is in the vast options it offers. The creative advantages lie in it's flexibility. That's what we should be conveying to new visitors. And, we should be encouraging their experimentation.