How to Read Stained Glass

Stained glass is something you read. To the 13th-century people who couldn't read, these windows were far more than pretty pictures: they were a real Bible. Just as a printed book has letters, words, sentences and pages, stained glass has its own grammar.

Pick one large window and look closely. It is actually made of several tall, narrow windows joined together, and each narrow vertical window is called a lancet. Each of the eight large side windows is divided into four lancets, and each of the seven small windows in the apse at the front into two. So one big window is four long, thin picture books standing side by side.

Each lancet is packed from top to bottom with small pieces of imagery. Each piece is called a medallion or panel, and it's the equivalent of one page in a book. A single window typically has anywhere from a few dozen to over 100 medallions, and across the 15 windows and the rose window they add up to 1,113. That is where the famous number 1,113 comes from.

What order do you read in? Not top to bottom, but always from the bottom up. You begin with the lowest medallion and climb steadily. For medieval people, rising from bottom to top symbolised human prayer ascending from earth to heaven, so the act of reading the images was itself a prayer, and with each scene you climbed, the prayer reached a little closer to heaven. But you don't simply go straight up: you read in a zigzag. The bottom row runs left to right, the next right to left, the next left to right again, climbing in a zigzag, much like following the lines of a book.

Colours carry meaning too. Blue is the colour of heaven and appears often, marking sacred figures or events, which is why the Virgin Mary's robe is always painted blue. Red stands for royal authority and sacrificial blood, the blood of Jesus, the Lamb, at once. We'll come back to yellow when we reach Window 0.

Have you reached Window 13? Here we'll look together at the story of the beginning of humankind: Genesis.