Everyone talks about oak in wine, or the lack of it. It is such a prominent matter of conversation that any wine-tasting in the world will inevitably be seasoned with talk of the wood that has become the number one natural container of choice in the world for winemakers. But what is oak? Why is it so important? Why do some winemakers use oak while others eschew it in favor of other containers like stainless steel?

It should be said that oak was not the first container to ferment or store wine, nor will it be the last. Through the ages, wine has been kept in terracotta urns, glass bulbs, porcelain boxes, stone holes in the ground, and a multitude of various woods. Oak just so happens to be the perfect sibling for a wine that seeks depth and character.

Inventive ways of making specific varietal wines using new technologies and myriad storage options are being created every year. That being said, there are few aids in a winemakers toolbox that carry the weight of an oak barrel.

Now, when we talk about oak in wine, we are speaking more specifically of a flavor compound in the wine that imparts a bit of the character of a charred oak barrel, when that barrel has been used to ferment and/or age the wine we are drinking.

There are various means by which that oak flavor can be communicated into a wine. One popular way among contemporary winemakers is to line the inside of a stainless steel tank with charred oak boards and ferment or age a wine in that tank. Slowly, over time, the wine absorbs into and passes through the wood and adopts the flavor of the wood.

Home winemakers sometimes use oak flavoring (powders, concentrates), or toasted oak chips that they can float in the wine. This easy and inexpensive method begins to impart flavor in as little as a few days and can really save a wine that might otherwise be undrinkable.

However, when it comes to the oak barrels that wineries use, the methods and techniques for getting the best attributes from each barrel and each wine is slightly different and more complex.

The easiest way of putting it is that as the wine ferments and ages inside an oak barrel it also oxidizes and concentrates by natural osmosis through the grain of the wood.

Keeping this in mind, the thickness of the staves of wood (that each barrel is constructed from) is of great importance, as is the tightness of the wood grain, and the humidity of the room in which the barrels are stored. For instance, a wine in a barrel with thin staves in a dry environment would concentrate and oxidize faster than the same wine in a barrel with thick staves and a room with higher humidity.

Ah, but what of temperature? Yes, the temperature of a storage room is also important. A barrel in a hot room will concentrate faster than it would in a cool room. This is one reason winemakers have used cellars to store wine rather than attics (Although some wines – Madeiras, in particular – are made in heated lofts), cellars are cool and humid.

About the char of the barrel – this too is an important note to make. How a wine barrel is built, shaped, and toasted is also relevant. One standard of tradition is aging a stack of oak staves for three years (one year for every centimeter of water loss in a one-inch-thick stave), then assembling the staves in hoops and bending the staves over heat.

Now, how much heat tells us the char or “the toast” of the barrel. The more a barrel is toasted the less it retains the grassy character of raw wood. However, a barrel toasted for too long can turn a wine bitter.

There are a lot of questions to ask when it comes to pairing wine and oak. For example, did the cooper (a barrel maker) leave the barrel over the flame for five or ten minutes? Was it a medium or heavy toast? Did he also char the heads (ends) of the barrel? Where did the wood come from? Is it American Oak, or Hungarian, or French? What forest did the wood come from? Did the trees grow long and thin or short with many limbs?

There are so many variables to the options of oak – it may seem daunting to also contemplate the thousands of coopers to choose from, and which wine to put in the barrel when it is new (barrels lose their oakiness over time), and how to treat the barrel when it is old and simply a neutral permeable container – that some winemakers decide not to use oak barrels at all.

One popular option is stainless steel. Wines made in stainless steel typically feature a more varietal-specific character because stainless steel does not permit oxidation or osmosis and therefore preserves a kind of static, young, fruity wine.

But let’s get back to barrels, and oak, and particularly the size of an oak barrel.

The standard barrel that most wineries use today will hold about 227-liters/60 US gallons. There are larger and smaller barrels, but this size seems to be perfect for aging most any wine by today’s standards.

So what does that mean? What are today’s standards? What is it that we are tasting that is so important?

For some, oak imparts tannin (Gallic acid) in a wine – a gritty backbone that parches the tongue.

For others, oak is a term used to equate a sweetness from the wood sugars that has absorbed into the wine and flaunts aromas of vanilla and smoke.

Ultimately, oak is what gives weight to wine. When used appropriately, it can rejuvenate what might otherwise be a bitter, insipid wine. Some purists suggest that using oak at all masks a wine’s uniqueness of place or terroir and the art of the winemaker.

The real question should be: Does the oak complement the wine or steal its thunder? Is the oak flavor a part of the wine or does it stand out and hide the fruit?

The end result is and always should be a balanced wine that leaves your palate wanting more.