As medieval builders became more confident they built their buildings higher and airier as though they were soaring heavenwards. This was a tricky thing to do architecturally speaking – the last thing that the average medieval bishop wanted was to be haranguing his congregation only to have the roof come crashing down round his ears.
The outcome was Gothic stonework called fan vaulting that reminds me of an avenue of elegant stone trees spreading out their branches to make a canopy.
My technical adviser (yes – that’s you Adam if you’re reading this) explained to me that you can create large spans that open up the space with fan vaulting. Each rib acts like an arch, meaning that the weight which might otherwise be disastrous effectively adds strength to the structure. Therefore you require fewer columns and can achieve taller buildings. You could compare fan vaulting to an egg-shell, in the sense that it gains its strength in its unity, it is form-active, so therefore less bulk is required for it to be structurally stable. The first fan vault that is still standing in the world can be found in Gloucester Cathedral.
A boss, which is after all what this particular blog is about, is a block of stone or wood, found on ceilings, at the intersections of the ribs of a vault. The more ribs that there are in a ceiling, both structural and aesthetic, the more opportunity there was for medieval masons to produce intricately carved roof bosses.
In Tewkesbury Abbey there are approximately 250 roof bosses many of them telling the life of Christ. The cathedral boasting most bosses is Norwich. 
Bosses may be foliage filled, depict green men with their mouths sprouting foliage, have birds, beasts and fabulous creatures as well as depicting scenes from the Bible – in fact the images on roof bosses depend on the imagination of the men who carved them. In the aftermath of York Minster’s terrible fire in 1984, the viewers of Blue Peter were asked to design some new roof bosses so one of them depicts Man landing on the moon.
Originally the bosses would have been painted but in the aftermath of the Reformation roof bosses often returned to the natural colours of wood and stone – some within reach of iconoclasts have lost their heads and hands. However, the majority of roof bosses are so high that the carvings remain in tact and there are often hints of the original paint as well.
Of course the downside of roof bosses is that you end up with a crick in the neck and lots of blurred photographs where your hands have shaken too much while you’ve been holding the camera at arm’s length – more photographic aerobic exercise. However, some cathedrals provide a tilted mirror on wheels so that visitors don’t need to do themselves a mischief to see the ceiling in all its glory. Provided that there aren’t lots of grubby paw prints on the mirror (and I have been known to clean them off) it is much easier to take a picture of the reflection of the ceiling than of the ceiling itself.
This blog contains three images. The first shows a roof boss depicting an angel playing a musical instrument that has been removed from the ceiling of Tewkesbury Abbey – there are several dotted around the building. The second image shows the ceiling of the nave in Tewkesbury. The ceiling has been restored to the way it would have looked before the Reformation. Medieval congregations must have been filled with awe when they entered vast colour filled spaces like this one – I certainly was. The final image – thanks to ‘he who is occasionally obeyed’- shows a boss in close-up in situ.
