ARTS / Exhibitions: Metaphorically speaking: Tony Cragg picks up prosaic things and hammers out a kind of poetry. Which is more than can be said for John Bellany

Fruit-juice squeezers, toy trucks, eye-baths, Walkmen - Tony Cragg is still using found objects in his sculpture. But the usage has been changing. His two new exhibitions in Glasgow, a big one in the great hall of Tramway, and a small one in the galleries of the Centre for Contemporary Arts, give an overview of the last few years' output. Cragg is only 42, but he is a senior figure in British sculpture, and his recent work is showing senior tendencies - away from playfulness towards something more monumental.

The earliest work on display, Crowd (1984), shows the Cragg who is still probably best known: the Womble with vision, the creative scavenger of urban jetsam, collecting thrown-away bits and pieces of coloured plastic, and using them as mosaic material - in this case stuck on the wall to make a frieze of larger-than-life people shapes. As found-object work, this was original but still in the classic mould (of which the classic example is Picasso's bull head made from a bicycle seat and handlebars). The found elements are assembled into some new form, but not themselves transformed. The improvised, half-mischievous ingenuity of the art requires that you use what you pick up, and no tampering with it. The operation is essentially witty, the effect one of surprise, a revelation of unexpected new possibilities. It's partly an artistic revenge on the world of manufacture with its confident functionalism, partly a rescuing of the object-victims of waste and obsolescence. Cragg's activity in this field was never too skittish or jokey (an occupational hazard). Minster (1987) creates three solemn spires from car tyres, cogs, tubes, a lot of round things with diminishing diameters, piled upon each other. The reassemblage is economical and convincing, but doesn't allow the incongruously un-churchy nature of its constituent parts to be forgotten.

What happened to Cragg's art in the meantime may be to do with what happened to Cragg: he got famous, he got rich, he got an atelier of assistants in the German town of Wuppertal where he now lives. And he began using more traditional, more costly and more laborious materials and processes - carving in stone, casting in bronze and steel. The world of already existing things still remains the basis of his work, but they are not its literal components. Now they lend only their forms, which are remade in these solid materials, often on a greatly enlarged scale, often in a very different form. Look at Subcommittee (1989): a towering cluster of office rubber stamps, cast gigantic in rusted steel, their bulbous handles suggesting a group of blank heads knocking together (a monument to bureaucracy). Or Walkman (1992): a block of grey-black limestone, carved with the features of a personal stereo, its buttons, cassette spools, headphones - a neat and beautiful piece, which takes the real Walkman's aspirations to be a compact solid little brick and remakes them, huge and hard. A Walkman in marble? You might expect the effect to be bathos but instead it looks (and feels - the temptation to touch is irresistible) like the destiny of the Walkman.

Cragg is not now so interested in the play of incongruities. The point, as he puts it, is to raise things out of their man-made designs, and to release their poetic or metaphorical potentials. Sometimes, as in several variations on laboratory flasks, he overworks the obvious sexual connotations of curvaceous, mouthy vessels. And sometimes the poetry is quite elusive - for example Untitled (Sugar Beet) of 1989, where sugar beets with Hallowe'en faces gouged in them and cast in a green patinated metal are laid along the shelves made by a stack of three I-bar girders. But the point itself is a good one - when it happens, which is not always. For in other pieces it looks as though his source objects are increasingly providing not metaphors, but only a vocabulary of pure shapes, with the echo of their original nature becoming fainter and fainter. He may use the forms of a juice- squeezer and toy trucks. But the idea of these things is actually submerged in the weight of their steel and stone enlargements, and in the sober authority of Cragg's formal compositions. You forget what they once were; often there seems little reason why Cragg should not simply be inventing his own forms, with no borrowings from the outside world. He is moving back into the tradition of abstract or semi-abstract work, the mainstream of Moore and Caro, with the found object as a habit that is hard to kick. Kondensor (1989), a construction of iron lumps and spirals, might easily be from Caro's factory. Though even in the newest work straightforward 'findings' still do crop up. There is a weird piece from this year called Angels and Other Antibodies, where wooden angels, appropriated presumably from an ecclesiastical suppliers, are porcupined all over with household hooks. But what the exhibitions show is a sculpture poised between appropriation and abstraction, and teetering too much in the second direction.

There is nothing submerged about John Bellany's metaphors. They are as plain as pikestaffs - or as skates or lobsters, to mention two of his favourite animal symbols. At 50, Bellany is a grand old man of Scottish figurative painting, a reputation that is (to me) mysterious. His exhibition at the Kelvingrove Gallery is called after one of his pictures, A Long Night's Journey into Day. It is not a retrospective but focuses on three key episodes in his artistic career - the nightmare allegories of the early Seventies, the pictures made around his near-death from liver failure and a subsequent transplant operation in 1988, and the more celebratory images of the last two years. The movement is from torment to exuberance, but they don't look so different.

Without being told, I don't think that you would naturally assume that Lovers (1991) was a celebration of sex, or that Woman with a Skate (1972) was an image of terror and disgust, as opposed to one of humorous gruesomeness - her response to fish-rape is an expression of prim irritation.

The trouble is not that, whatever the mood, Bellany's sensibility is lurid, or that the imagery is overt. These things can be done with conviction, but it does matter that the drawing is a very rough- cut kind of caricature, that the physiognomies employ a narrow range of devices, and that the colour schemes conform to a seldom varying recipe. The primaries - red, yellow and blue - predominate with an unpleasant bias towards yellow, and they are put down with little tonal contrast, which tends to remove focus from the compositions. Almost every element of the picture is emphasised, as though the painter were reluctant to let in a low key lest he should appear less than absolutely intense. But surely you need some discrimination of energies. And to come across a single living face in these pictures - which you do occasionally, for instance that of Bellany's wife in Sunset Song (1989) - puts the rest of the palaver into perspective.

Cragg: Tramway, 25 Albert Drive, Glasgow (041-422 2023), and CCA, 346-54 Sauchiehall St, Glasgow (041-332 7521), both to 6 Sept. Bellany: Kelvingrove Gallery, Glasgow (041-357 3929), to 30 Aug.