SECRETS BELOW THE SURFACE

"BECAUSE the X-ray machine can penetrate the surface of a painting without doing any damage, it has long been an indispensable tool for art historians. Layers of paint on canvas (including the liberal amounts of white lead used by old masters to lighten their pigments) absorb X rays in varying amounts, thus producing on a negative a revealing shadowgraph. To the trained art scholar's eye, an X ray of a painting can often reveal its whole history, from the first unseen priming coat the artist put on the canvas, through the artist's corrections and overpainting, to the final surface that meets the gallerygoer's eye. Last week two questions that have long been debated by art scholars were answered by X ray.

In Chicago & London. One answer came in Chicago, where the mystery was whether Georges Seurat had originally included his only self-portrait as a mirror image in his famous painting of his mistress, Young Woman Powdering. Chicago Art Institute Director Daniel Catton Rich and Painting Conservator Louis Pomerantz, taking advantage of the loan of the painting from London's Courtauld Institute for the Chicago Seurat show (TIME, Jan. 20), decided to test the legend by X ray. To their delight, they found beneath the paint the blurred outline of a man's head. The discovery tended to confirm the tale that Seurat had painted it over after a friend had pointed out that it would be in dubious taste.

The day after the Chicago Institute announced its discovery, the Courtauld Institute announced in London that it had found an answer to an older puzzle. Among the paintings owned by Queen Elizabeth is one attributed to Titian, titled Titian and Friend. For generations scholars have been troubled by the disturbing blank area at the right of the painting. Placing it under X ray, the London institute discovered a long-suspected third figure, a man younger than the others. Experts have guessed that Titian's first friend was Venetian Grand Chancellor Andrea dei Franceschi, but Friend No. 2, and the reasons why he was brushed out, are unknown.

At Ferrara. One of the most impressive feats of art sleuthing by X ray is reported by John Walker, director of Washington's , National Gallery, in his book, Bellini and Titian at Ferrara (Phaidon; $6.50). Sleuth Walker tackled one of the world's great masterpieces, Giovanni Bellini's Feast of the Gods (see color page), now at the National Gallery, managed to prove through X rays what no scholar could hope to do with the naked eye.

Art historians long ago confirmed the ties between Bellini and Titian. Bellini, the master of 15th century Venetian painting, was more than 80 when he delivered his Feast to the proud, warlike

Duke Alfonso I d'Este of Ferrara and his wife, Lucrezia Borgia. Bellini had called on the young talent of Titian to help finish the great canvas. After Bellini's death in 1516, Titian--who became the new Venetian master--won the commission to paint three other large, allegorical paintings for the duke's Renaissance study. As an added service, Titian repainted sections of the Feast to make it accord with the more luxury-loving tastes of his time--and, incidentally, to accord more with his own oils.

With these facts to go on, John Walker decided that he would try to separate Bellini's original work from Titian's later additions. By meticulously X-raying the canvas (14 negatives were used to cover the figures), Walker was able to pinpoint those aspects which made Bellini seem oldfashioned, and reveal Titian's solutions for bringing them up to date.

Over the static row of trees that Bellini had used as background (see X ray opposite), Titian painted a tremendous, craggy landscape that historians consider "an epoch in the history of art." Slicing down across the canvas is a torrent of light leading the eye to the fertility god Priapus in the act of surprising the sleeping nymph, Lotis. (The rest of the story, i.e., that the satyr Silenus' hollow-backed ass, at left, would bray at the critical moment, thus awaken the other gods and put Priapus to flight, was then too well known to require illustration.) Elsewhere, Titian lightly brushed in the gods' symbols, e.g., the trident for Neptune, lowered the decolletage of the nymphs, changed legs and arms to weave the static figures into a more rhythmic whole.

Loveliest Nude. Using his X-ray evidence, Walker was able to give art scholars a full report on one of the greatest art criticisms ever delivered. Moving on from Titian's embellishment of his master's work. Walker points out that the younger painter challenged Bellini even more directly with a nude figure in The Andrians, the painting which originally hung alongside Feast in the duke's study. Considered one of the loveliest nudes painted during the Renaissance, it seems to be Titian's statement to Bellini: "This is how your Lotis should have reclined if she were to charm Priapus."

In time, even Titian's resplendent nude became oldfashioned. A century later, when the great northern baroque artist, Peter Paul Rubens, copied The Andrians, he rendered the nymph as a quite human figure. Pointing up the changes, Walker writes: "Titian's maenad seems wrapped in dreams, the marvelous sensuality of her pose dowered with a poetic beauty. Rubens alters slightly the position of her head and arm, and suddenly the nymph assumes the heavy somnolence of intoxication. She has fallen into a drunken slumber wonderfully expressed."

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