Piero della Francesco will always stand out in my memory of studying the History of Art at Oxford University. In the first module of the first term of the Certificate course we listened to the wonderful Mary Acton explaining how to look at paintings. She used a number of themes to illustrate her lectures:  composition, space, form, tone and colour, as well as subject matter.

The Baptism of Christ, by Piero della Francesco, she used to illustrate composition and, in particular, the interplay of verticals and horizontals. This great painting in the National Gallery in London, in her words, “radiates stability and peace combined with spiritual tension and mystery”.

We were then invited to describe the vertical and horizontal elements. See if you can find five of each. The most important is the vertical of the tree trunk. It seems to establish two differing scenes. The first, the familiar one of John baptising Christ in the River Jordan, with the dove, the Holy Spirit, vertically above, and a second one of the angels on the left.

The proportion of the scenes on either side of the tree trunk act to illustrate what Mary Acton called the Golden Section. This emphasises Piero’s love of mathematics and perspective. He in fact gave up painting in later life and wrote treatises on mathematics. 

The Golden section has been used by many artists from the renaissance to modernity to portray what might be called a pleasing proportion. The section is based on the ratio between the two portions being the same as that between the larger portion and the whole. Difficult to quantify exactly mathematically it is close to the ratio between unity (one) and the square root of two. Try it out for yourself. Piero della Francisco used this same section in his masterpiece at the Palazzo Ducal in Urbino, The Flagellation of Christ. Look for the pillar Christ is tied to within the frame of the building. This very enigmatic painting has confounded art historians for centuries but maybe an allegory for the Turks mistreating the Christian church in the fifteenth century. A debate for a future post, maybe.

Mary Acton’s revelation about The Baptism of Christ, though, is that while the painting is composed of key vertical and horizontal elements, they are not straight or continuous which delivers the work from the risk of being an autonomously mechanical work. Look for the angels clothes trespassing to the right hand side of the tree trunk, the weight shifts away from the vertical of both Christ and the Baptist. These variations are not accidental but carefully planned out by the artist.

When in front of paintings by Piero della Francesca, also look for his trademark expressionless faces. The emotion is only hinted at.

When someone as inciteful and enthusiastic as Mary Acton asks you to ‘learn to look at paintings’ it becomes a truly enjoyable experience. Try her book; Learning to Look at Paintings (Routledge, 2009}