The artist often swapped painting for etching as a way to rediscover his craft. Now a new exhibition shows these flashes of inspiration in all their intimate gloryAt home one evening in 1951, Lucian Freud did three drawings of fellow artist Francis Bacon. The biographer William Feaver recounts the anecdote as Freud told it to him: Bacon had stood up, undone the buttons on his trousers, rolled up his sleeves and wiggled his hips a little, saying: “I think you ought to do this, because I think that’s rather important.”By Freud’s own admission, the older painter was provocative in more ways than just this pose: “I got very impatient with the way I was working. It was limited and a limited vehicle for me,” Freud told Feaver. He felt his drawing stopped him from freeing himself, he said, “and I think my admiration for Francis came into this. I realised that by working in the way I d...