Had Louis been a politically calculating monarch, he would have weighed carefully whether his investment in relics might generate a sufficient temporal return. Louis IX was not politically calculating. He was devoutly religious, and probably would have spent more for his prized relics if it was necessary. As the most pious of the French monarchs (which probably isn’t saying much), the Catholic Church saw fit to grant Louis IX sainthood, so it is to Saint Louis that we owe what is left of his reliquary, which is nothing if you consider most of what he bought were fakes, but everything when it comes to Sainte-Chapelle, the most astounding collection of stained glass windows in all of Christendom.
To uncover the architectural secrets of Sainte-Chapelle, we need to know something about the architectural style of its day and age, known as Rayonnant, which is French for radiant, and refers loosely to the radiant rose windows that appeared in Medieval cathedrals from around 1150 to 1250. We should first, however, take a tour of Sainte-Chapelle, with the understanding that no photograph or film can completely capture the sense of being surrounded by colors when you are standing within Sainte-Chapelle. We will see, in succession, views of the exterior, the interior of the chapel from the floor, the altar with the four-posted reliquary for the Crown of Thorns, the Crown of Thorns (no longer displayed in the chapel), three of the fifteen stained glass windows, and the Rose Window at the rear entrance to the chapel.
In the next two pictures, compare the flying buttresses at the rear of the cathedral of Notre Dame de Paris, which is within walking distance of Sainte-Chapelle on the Ile de la Cité, to the walls of Sainte-Chapelle. The posts between the window panels at Sainte-Chapelle are very thick and come outward from the building. In a sense, the architects for Sainte-Chapelle chose not to put up a lengthy wall and set stained glass windows within a defined, but wide, expanse of wall necessary to carry the weight of the building. Instead, they took what would have been the length of each segment of wall, and turned it sideways, on a perpendicular line to the windows. The supporting weight is still there – it merely comes out from the building, but without any of the distraction of a flying buttress. You don’t notice this when you are inside the chapel, because these perpendicular supports are hidden behind thin half-columns.
The stained glass windows themselves are among the best preserved such windows from the Gothic, or Medieval, era. As is the case with windows in Gothic churches, they tell Biblical stories from Genesis on to the New Testament. I present next some close-up views of the stained glass, to give you a sense of the detailed work in each of the rondels and the variety of colors used, especially blue, which was the most expensive color to produce because it required cobalt to be added to the glass during the firing process. Cobalt was difficult to obtain.