A glass half empty at the National Gallery's Art of Light,Yazzy's at www.williamverdult.com

According to Timesonline.com, you probably know that God said “Let there be light” – and there was light. And you may also know that God saw the light and decided it was good. Indeed, it was very good. But what you may not know is that this happy state of divine affairs, described in the Bible’s first breaths, continued for many millennia, until about 1500, when, in Germany, a group of glass artists emerged who took the light thing somewhere else. If you don’t believe me, pop along to the National Gallery, where a small display devoted to German stained glass of the Renaissance demands a big examination.

I should probably admit immediately that when it comes to stained glass, my judgment is unreliable. I’m besotted with the stuff. There’s something that happens to light when it passes through coloured glass, particularly blue glass, that seems to focus it on my heart and turn me all queer.

A particularly cranky Swiss modernist called Johannes Itten ran a course in stained glass at the Bauhaus, and a few years ago the Guggenheim in Venice hosted an exhibition devoted to Bauhaus glass that included his fascinating ramblings on the subject. Itten insisted that each colour of glass affects you differently. His contention was that stained glass avoids the brain altogether and appeals directly to the nervous system. In other words, you can’t help feeling what you feel in front of coloured glass. It doesn’t matter if the artist who made it is good or bad. When light passes through glass, it does something to you.

I can personally vouch for the truth of this claim. The first time I stepped into Chartres cathedral, as a young art-history student on a class outing, dutifully doing my rounds, I started crying. Not from sadness or pain, but from sheer, breathless awe. The windows attacked me. It’s happened again on numerous occasions. Regular readers of this column will know I am not generally a wholehearted admirer of Matisse, whose work I often find decorative and limp. But the stained glass that Matisse installed in his gorgeous Chapel of the Rosary, in Vence – where it isn’t any old light streaming through the blue glass, but the particularly dangerous Mediterranean light – left me blubbing like an abandoned toddler. Light becomes something physical when it passes through glass and hits you in your chest.

Fully aware of this weakness in my critical faculties, I approached the National Gallery’s small survey of German stained glass expecting to be quickly and fully intoxicated. Interestingly, it didn’t happen. The show’s thesis is that the art of stained glass reached its apogee in Germany in about 1500. Not just because the craftsmen of the era invented and perfected a range of techniques that took stained glass to extraordinary levels of possibility, but because these pioneering glass artists were being influenced, and abetted, by their famous brethren in the painting fraternity: Dürer, for instance, and Hans Baldung Grien.