A bill for 20 grams of Pure Gold, for one painted area of sensibilized immaterial. [about 1958, text on a bill for selling 'air'] - Yves Klein

It was then that I remembered the colour blue, the blue of the sky in nice that was at the origin of my career as monochromist. I started work towards the end of 1956 and in 1957 I had an exhibition in Milan which consisted entirely of what I dared to call my 'Epoque bleue'.

I made the flames lick the surface of the painting in such a way that is recorded the spontaneous traces of the fire. But what is it that provokes in me this pursuit of the impression of fire? Why must I search for its traces? Because every work of creation, quite apart from its cosmic position, is the representation of pure phenomenology – every phenomenon manifests itself of its own accord. This manifestation is always distinct from form, and is the essence of the immediate, the trace of the immediate.

I want to take as the canvas for my next picture the entire surface of France. This picture will be called 'The Blue Revolution'. It isn’t the fact of my taking power in France that interests me, but rather the possibility of creating a monochrome picture in my new manner: ‘The Refinement of Sensibility’.