Sir Joshua Reynolds, the painter who persuaded 18th-century society that it was OK to have its portraits painted by a British artist, was a man obsessed with process.
In order to discover the technical secrets of Titian, Rubens and Watteau, "Sir Sploshua", as the wiseacres called him, bought works by them and dug into the layers of paint. And to produce in double-quick time the effects achieved by the old masters, he dabbled with a variety of materials, including solvents, resins and eggs.
The artist Benjamin Haydon reckoned that some of Reynolds' paintings were "varnished three times with different varnishes, and egged twice, oiled twice, and waxed twice, and sized 6, perhaps in 24 hours!"
Exaggeration from a jealous rival? It seems not. Even in his own day, the extent of these dubious techniques, and some of their more unfortunate consequences, were common knowledge. Chief culprit was a tarry substance called asphaltum, lumps of which were dissolved in oil and turpentine and applied as a glaze. In the short term, this gave the work the mellow tone of a Renaissance masterpiece, but it very quickly resulted in fading and worse. One aristocratic sitter returned in poor health from abroad to discover his once youthful portrait, like that of Dorian Gray, had aged even more than he had. And the story was told of how a boy, delivering a Reynolds portrait, knocked into a railing, whereupon the entire face fell off.
Sir George Beaumont, recommending the artist to a friend, brushed aside such worries: "Take the chance," he said. "Even a faded picture from Reynolds will be the finest thing you can have."
But when the artist died, this enviable reputation deteriorated as rapidly as his colours, so dull and lifeless did his legacy now appear. William Blake, never an admirer, wrote somewhat gleefully that, when Reynolds passed away, "All Nature was degraded; The King drop'd a tear into the Queen's Ear, And all his Pictures faded." Everything he achieved in his lifetime was now spoiled, and all for a ha'peth of tar.