Great Works: Head Study for St John the Evangelist (c1579) by Federico Barocci

National Gallery of Art, Washington, DC

Such hair! Who in his right mind would ever volunteer to do without it? Yes, in life, as in art, hair is of great moment. Think of the hair of Bacchus in Titian's Bacchus and Ariadne at the National Gallery, how the flight of it, partially interwoven with leaves, seems to embody his wildness, his outrageous proposal to Ariadne that she might wish to wed him in exchange for receiving the sky as a nuptial gift.

The impulsive movement of his body as he leaps headlong out of his chariot towards her seems to be given that much more energy by the nature of his hair. Or think of the awful burden of hair that is suffered by Dante Rossetti's disgustingly syrupy womenfolk, how it drenches them in grossly immoderate sensuality as if they were so many over-rich cakes heaped up on a groaning table.

The hair on this page is very special too. The image itself, which is a head study for St John the Evangelist, was later incorporated into a great altarpiece of The Entombment of Christ, and it is currently being used – in fact, somewhat misused thanks to the characteristic crassness of the advertising man – to draw attention to a magnificent show of work by Federico Barocci at the National Gallery.

You can see it on every poster, this wonderfully ebullient hairscape. Except that, alas, you cannot quite see it because it has been cropped, and then partially obscured by information. This is tragic because the hair helps to give emotional definition to the work. Cropped, we concentrate upon the flushed cheek – this flushing of the cheek happens again and again in Barocci, and so when we see it in near isolation from the full swing and fling and fly of the hair – as on those posters – it shrinks to a slightly tiresome mannerism.

At the National Gallery itself, the study hangs beside a second one of this exact same pose and, just a couple of metres away, the dramatic altarpiece itself. Often a study for a painting looks more vitally alive than the near-perfect copy of it which subsequently appears in the painting itself. This happens a great deal in Rubens. His enormous, finished canvases often feel like little more than bravura exercises. Their emotional impact is much less than that of the detailed studies in which they began their lives.

Something similar has happened here. This first study is a wonder. It looks and feels impulsively provisional, a wave of feeling that has been caught on the ebb or the flow. The second study is much more resolved, much closer to the head that we can see in the painting itself. (It may even have been painted after the work was finished.)

So much of the emotional impact of the earlier study on this page depends upon how he has painted this blurry cloud of auburn hair – its soft, hazy, wispy featheriness; how it spirals away from the crown of the head in an unruly fashion, or slips down, partially concealing the right ear, in thin, wayward threads. This is hair as indicative of emotional disarray, hair that has been slept on, hair that is not being attended to because there is the terrible, distracting burden of everything else.

The altarpiece shows us what that else is: the young St John, Christ's most beloved apostle, is helping to bear the weight of the dead Christ's body, which is being carried on a sheet towards its resting place. We know nothing of all of this in the study, and it is good that we do not because the altarpiece is not entirely successful.

In fact, there is bathos at its centre. Christ himself looks as if he is taking a post-prandial snooze in a convenient hammock. Oh well, this is hardly the first time that a great painter or writer has failed to lend conviction to the embodiment of overwhelming goodness. We can appraise the study without the burden of all this religiosity, admire it for itself alone, as the capturing of a mood and a moment.

About the artist: Federico Barocci (1535-1612)

Federico Barocci was born, like his great predecessor Raphael, in the town of Urbino in the Marches of Italy in 1535, and much of his life was spent working in that area. In the 1550s he moved to Rome, but during a second visit to the Eternal City he was poisoned during a picnic, allegedly by jealous rivals, and in 1563 he returned to the city of his birth, where he remained for the rest of his career, influential and extremely highly paid.