From the exhibition webpage:
The abbey church of Conques, the place where Soulages found his vocation, is also the place where he consecrated his career. The stained glass windows commissioned by the State in 1986 were installed in 1994, after eight years of research. Wishing to place this work within the logic of his artistic development without thereby making the windows a mere extension of his painting, he decided not to make any preparatory drawings before having determined his material or rather having been determined by it. This material was a colourless glass whose translucency could be modulated. This glass did not yet exist, but he had it made for the occasion.
Intended for the abbey’s 104 openings, Soulages’ windows are made up of large bands of untinted glass. These bands have gradations of variable opacity present in their very thickness. Thanks to the material, translucent and not transparent, the openings give the appearance of surfaces which are their own source of light. The parallel bands have the same width and are grouped in horizontal compartments. Their sloping angle and their curvature vary depending on their position in the window, producing, more often than not, an effect of upward tension. Seen from inside in the evening, the panes can simultaneously take on different red and yellow hues on one side and blues and greens on the other. Seen from outside, they reflect the light of the sky like so many opaque mirrors, becoming as impenetrable as the stone façade. It is a factor which Soulages was very interested in, as his windows were made to be seen from both sides: thus the yellow on the inside can look blue on the outside, as it reflects the sky. Once again, by reducing the means employed and letting the environment play its part, he reveals the infinite richness of light.