Stained glass makes an impact on the senses unlike any other art form because of its brilliance and ever-changing movement as it responds to the light of the sun. Reaching many people simultaneously through the use of light to power the generation of bright colours, it was arguably the first modern medium of communication. Not until the invention of cinematography could a greater number of people view images transmitted by light, and not until the invention of television could more people view the same images simultaneously, as in a medieval cathedral. Wall paintings use reflected light to illuminate a mixed palette and have never been able to rival the brilliance of glass.

Stained glass uses a technological breakthrough whereby oxides held in clear glass can absorb the light waves of one colour to create another. Natural colours cannot rival the arresting power of stained glass because it is a filter that produces a frequency of light that has been isolated in a pure form. Stained glass was the ideal mode of expression for the complex ideological messages that the community at Canterbury wanted to promote about itself at the end of the twelfth century. The international reputation of the Cathedral was enhanced by its stained-glass windows, and despite the depredations of time, iconoclasm and war, the glass remains one of the cultural treasures of Europe.

A living tradition of stained glass at Canterbury, inspired by the past, has also produced some of the most important windows of the past two centuries. The creation, care and conservation of stained glass, as an essential part of the fabric of the Cathedral, started in the twelfth century and has remained at its heart.