ART / Exhibitions: Whaam] Pop] The bubble bursts: Comic books could give Roy Lichtenstein style, but not substance. A retrospective at Liverpool's Tate charts his progress to immaturity

THE Liverpool Tate has put on a well-judged retrospective of Roy Lichtenstein, but something is missing - a large chunk of his artistic life. Lichtenstein was a quite different painter before his controversial cartoon-like pictures appeared at New York's Leo Castelli Gallery in 1962. For a dozen years he had painted and exhibited, with no success, canvases that crossed French influences with American themes, mostly taken from the cowboys-and-Indians painter Frederick Remington. There is no sign of this in Liverpool; and the more one looks at Lichtenstein's later paintings the more intriguing seems the absent (suppressed?) art of his novitiate.

So this is not a complete retrospective, especially since we expect a chronological account of an artist's work to show growth. The satisfaction of any retrospective is to see how someone reaches maturity. To say that Lichtenstein became mature when he first started to imitate comic books would be idiotic. Some things have changed since those days. His design is bolder and often more complex. He has given up comics and turned to imitating earlier fine art. But the essentials of his manner remain the same, and it looks to me as if Lichtenstein's maturity consists only of the degree of sophistication he employs in criticising other people's paintings.

For these reasons alone, I hesitate to call him a major or an innovative artist. There is a simpler reason why we cannot see Lichtenstein on the level where art really matters. His pictures do not move us. They shock some people, as we know. They intrigue and excite. I like them for other reasons too. But they have no heart. The older he has grown - he is now 70 - the less he engages with the emotions of humankind. 'Oh, Jeff . . . I love you too . . . but . . .' 'I know how you must feel, Brad . . .' 'That's the way . . . it should have begun] But it's hopeless]' Such comic-book sentiments filled his first famous pictures. Obviously he could not have continued them for ever. None the less, those trite declarations had their point. For one thing, they signalled that adults could sympathise, at a remove, with the new world of Sixties adolescence. When the captions disappeared, something was lost. I feel that Lichtenstein then became an adolescent in art, clever but also chilling.

Significantly, the most genuine picture in the show is the first, a small one from 1961 called Red Flowers. Here are the elements of Lichtenstein's Pop art, the Ben Day dots, the flat colours, the bold upfront design suitable for mechanical reproduction. However, Red Flowers is evidently hand-painted, and its manner is that of a person who knows how to do art-painting but has dropped most of that knowledge in favour of naivety. This was an exact transcript of Lichtenstein's situation. He was nearly 40. For years he had been toiling at this highbrow modern art business, and it had got him nowhere. He liked popular American culture. But he did not have an American way of painting. Could it be that comics, rather than Remington, might provide him with such a style?

Yes; but note that there is now a further confusion about his artistic (as opposed to his chronological) age. We know Lichtenstein began the paintings of Mickey Mouse and so on to amuse his children. The tender feeling of Red Flowers may come from this. But Lichtenstein also found he was diverting himself, and becoming younger. It wasn't exactly child's play, this comic art, but all the years of his apprenticeship fell from his shoulders. The burden of being a laborious adult artist was lifted. Pop was born. And after his first Castelli show Lichtenstein was rich and famous. Was this because he had become an artist at the height of his powers and imagination? No.

Pop art in general declined as soon as it appeared. Individual Pop artists have never been more interesting than they were in their first heyday, a short period that coincided with the end of the Kennedy administration. Lichtenstein's return to a boyish outlook was not unique in early Pop. Andy Warhol had been an obscure artist for just as long as Lichtenstein. His first little gold pictures of Marilyn Monroe, still his most affecting works, must have been inspired by the cheap icons of the Catholic Pittsburgh in which he had been raised. Jasper Johns's first American flag paintings, so much better than their later variants, were like naive art preserved in an ethnographic museum. Such reversions to childhood, or to the condition of being untutored, look good to this day. It's the subsequent careers of Warhol, Johns and Lichtenstein that turn out to be disappointing.

They were never a group and had no temperamental affinities. Lichtenstein's course after the invention of Pop has been especially lonely. He had no comrades within the enterprise of modern art: nor, I guess, within the world of comics. Commercial artists must have been dismayed to see that their sort of work, usually done anonymously and with little reward, could be so easily transferred to uptown Manhattan galleries. For the Sixties Lichtenstein was a faultless star in the public arena. His paintings thrilled everyone, except other painters.

Perhaps this is why he was to turn on art, mocking other people's pretensions and the icons of modernism. First, though, he went through a phase that seems today to be dated and socially off-key. Like the comics that were his models, Lichtenstein's paintings were either for girls ('I tried not to think of Eddie . . . I'm not hungry mother] Please, I just want to go to my room]') or for boys ('Takka Takka, Varoom] Okay, Hot-Shot, okay] I'm pouring]') The best of the male type is Whaam] of 1963, very familiar on this side of the Atlantic because it belongs to the Tate and is among the gallery's best-selling postcards.

Technically - ie, in terms of its design, organisation and professional facture - I count this the best of Lichtenstein's comic-book paintings. Perhaps I also like it because I'm reminded of being a boy. Takka Takka] But apart from the painting of a school exercise book, Composition II, this show does not contain many more of the juvenile themes of the Sixties. It has been selected by Judith Nesbitt, who has sought loans with great care and created an impressive installation. Her concern, I fancy, has been to concentrate on the Lichtenstein paintings that take an ironic look at modern art. Thus he is placed squarely in the post-modernist camp - as a cool but entertaining critic, an artist who shuffles previous images and would not be so old-fashioned as to actually create them.

So Lichtenstein's career takes a different shape. He proceeds from being a failure to being a committed anti-modernist, with three or four intervening years when he mulled over Mickey Mouse. His critiques of modern art are superbly done, even though they make no lasting point and would look terrible if set beside the real work of the masters Lichtenstein is concerned to deconstruct. So here, all in Ben Day dots, are deadpan parodies of Mondrian, Picasso and the purist art of Twenties Paris, so efficient that they might have been painted by machine. That, of course, is part of the game.

One modern master above all haunts Lichtenstein. This is Willem de Kooning, the abstract expressionist who was at the height of his fame when Lichtenstein was a nobody. De Kooning's brushstroke was parodied from 1965 onwards and a 1981 picture takes off his 'Woman' series. Next to the later false de Kooning hangs a painting I don't understand, perhaps because it appears to have been made without the aid of stencils and with no original in mind. Could it, like the demure Red Barn of 1969, refer to the regionalist painting that Lichtenstein was doing before he turned to Pop? Is it possible that he still sometimes tries straight painting, as a hobby or a relaxation?

Liverpool Tate to 18 Apr (051-709 3223).