Most wines get more complex, developed, dimensional, and enjoyable as time goes on, but before our favorite wine makes it to the pretty bottles that fill our wine cellars and scatter our tabletops, it needs to age. This important stage between fermenting and bottling is called élevage, which can take a few months to several years.

The material of the barrels is a very intentional choice by the winemaker, as oak barrels require a longer aging process for the wine to benefit from the flavors and aromas of the wood. Oak barrels allow for oxygen exposure, provide tannins, and impart flavor to the wine when aging, but it comes down to how the grapes respond to the barrel and what type of final product is desired.

Stainless steel barrels are the opposite as they don't expose the wine to oxygen, affect tannins, or impart flavor. They are more common for white wines and are used for grapes with no or low tannins that are already fruity or aromatic, such as sauvignon blanc or grenache — something with a flavor the winemaker doesn't want to mask or obscure with oak.

Meanwhile, oak barrel aging adds more texture and an oaky flavor to grapes that benefit from that maturation. For example, it can give more complexity to a neutral, aroma-less grape, such as Chardonnay, or add notes of vanilla, caramel, or smoke to a cabernet sauvignon, which can withstand the oak's strong flavor.