Power, surfing and French knitting: South African sculpture is diverse in the extreme, writes Chris Roper

If you were scripting a showdown between the young guns of sculpture in South Africa, you couldn't do better than the current scenario. There are four superb exhibitions on in Cape Town at the moment: Paul Edmunds's Cloud at the João Ferreira Gallery, Wim Botha's Speculum at the Michael Stevenson Contemporary, Jacques Dhont's DecoDhont at the Dorp Street Gallery, and Alan Alborough's work[ing/in] pro[cess/gress] at the Sasol Art Museum.

Visit all four in a 24-hour period, as I did recently, and you'll be reeling from the impact of the works. There's nothing restrained about the work these sculptors are doing and they are uncompromising in their artistic vision. Indeed, the danger for a critic is that you are tempted to lapse into effusive poetic metaphor in an attempt to convey the beauty and power of the majority of the works. But superlatives would not really do these artists justice. The most successful of the works aren't compromised by the necessity of having a thematic or narrative structure attached to them.

True, Botha's sculptures are created around the motif of the coat of arms. Edmunds's almost amorphous creations speak of a rigorous examination of warp and weft. Dhont's strange insectile shapes are invested with organicism that allows, even encourages, viewers to imagine that they recognise what they are looking at, and Alborough's clinical, industrial construction is a take on the craft of knitting. But the best of their work achieves that almost miraculous simultaneity of opacity and surfeit of meaning that characterises great abstract sculpture.

Botha's Speculum is made up, in the main, of variations on the traditional coat of arms. These range from a work consisting of nine rich red stained glass windows with gilded frames - each representing a section of the coat of arms - to Scorched Earth, a scarred and distorted neon and plywood sculpture of the United Nations' crest. The finest work, though is made up of lengths of silvery fishing line strung taught between two walls dividing the room with a dangerous looking, shimmering barrier.

The line is attached to the outlines of a coat of arms pricked out on each wall. The effect is that the air appears to be sliced by almost intangible lines of force holding together the essence of what a coat of arms can stand for. It is a work that challenges and pleases, but the initial impact of its beauty is not reliant on any obvious ideological or narrative point.

This contrasts uncomfortably with the obvious visual puns in Fatherland and Motherland - two artificial marble renderings of the coat of arms, the one characterised by a phallic protrusion, the other by a vaginal declivity.

One of the dictionary definitions for Clouds - the title of Edmunds's exhibition - is "something that obscures". This is not what the works on show do. If anything, they strike the viewer with blinding clarity. Granted, you're not precisely sure what has become clear, but you are aware that some great universal secret has been revealed and that you are happy.

Hmm ... I sense that I have just fallen out of reason into emotion. And yet, one can't help it, when confronted by a sprawling and shimmering piece of woven silver mesh, or a squatting, vaguely ovoid and milky white construction of cable ties and plastic mesh.

The latter work, Sieve, is beguiling. A mesh is rendered in three dimensions. The angle at which you look at it changes what you see as well as the depth to which your glance penetrates. The way light bends around it creates an adequate metaphor for the way the work bends your understanding and experience of time and space. Its meaning is made less dense by a companion work, a video that loops two simultaneous screenings from a surf movie on a split screen, making the two streams ebb and flow against each other.

One of the strengths of Edmunds's work is the way in which his art stands eyeball to eyeball with incomprehensibility, and wrests a grudging meaning from it. The surf video compromises this confrontation, while providing the nervous viewer with a welcome visual lexicon to articulate a response to the larger works.

Alborough's tediously named work[ing/in] pro[cess/gress] is marvellous. A constantly evolving sculpture that manages to suggest haphazard growth and scientific precision at the same time. Based on the concept of French knitting, Alborough's sculpture is difficult to describe. From spindles attached to the balustrade of the central aperture hangs a plastic rope and attached to the ropes are numerous small, blue buckets.

The sculpture is made up of a number of shapes, elements and materials, producing a dizzying array of surfaces, lines and planes to discipline the eye. The work seems only tangentially about knitting and more about the proliferation of objects that are necessary to create a utilitarian product.

In an annexe, there is a display of children's art, the products of workshops run by Alborough. Their amateurish work contrasts dramatically with the laboratory-like precision of Alborough's vision and accentuates the importance of materiality in understanding what his work is about.

Three sculptures, three descriptions. They exist on a continuum from the entirely abstract to the marginally representational, but are characterised by a depth of vision and studied economy of execution. They also display great beauty, and award the viewer with equal amounts of satisfaction and frustration.