Oak is the Wonderbra of the wine world. It offers shape and comfort to the user and provides wine with seductive padding, support and contours. In the past 20 years, oak has run rampant, dominating wines from Europe to the southern hemisphere. While there is no question oak enhances wine's 'silhouette', many winemakers push it to the extreme, with Domaine Laurent of Nuits-St-Georges boasting use of '200 per cent oak'. Overtly buxom appeals to some, but beware: there must be something interesting beneath. Otherwise, one is left with a sagging structure and the inevitable droop. Why are oak and wine so intimately acquainted? For centuries, Mediterranean producers relied on clay jugs called amphorae to ship wine, while those in inland regions, such as Rioja, Spain, used pig skins. As wine production spread, forested northern Europe opted to store wine in oak barrels. Fine-wine producers soon realised that oak imparted flavours to the wine far superior to those of pig skins and clay. The two dominant oak suppliers are the United States and France, although barrels are sourced from many other wooded regions around the world, including Central and Eastern Europe. American oak has a vanilla and coconut influence on wine, whereas French oak imparts a spicy character to the liquid. Modern science argues that flavour is dictated by the technique employed in a barrel's production rather than the oak species used. How the wood is cut, dried and seasoned has much to do with the barrel's ultimate flavour profile, but the most important influence is the heat used to shape the casks. To configure stiff, corset-like oak staves into a pleasing round shape, the barrels are warmed over open flames before being forced into a series of heavy steel bands. Any woman with an underwire support system will appreciate the effort this requires. Heat levels facilitate pliability, but also change the wood's inherent character. Thus, an oak barrel that was shaped over high flame will infuse a smoky, almost coffee-like flavour into wine. Oak shaped with minimal heat will inculcate a delicate vanilla profile and oak with 'medium toast' is likely to impart a spicy, clove-like flavour. While oak can lift and separate the sublime from the ordinary, many contemporary winemakers are reining back their exuberant use of oak, especially those in Australia, where wines were once so overtly laden with oak flavour that Yarra Valley winemaker Serge Carlei referred to them as 'wines with breast implants'. 'They hone you in and get your attention,' Carlei says. 'But when you touch them, they're not the real thing.' These days, many Australian winemakers are producing classic oak-matured wines as well as a range of 'unoaked' labels. The Wonderbra was hugely - no pun intended - popular in the 1990s. At present, we're in the reactive, burn-your-bra 00s. Neither look is sexy without underlying fruit and structure; it's all a question of balance and proportion.