Since the beginning, wine has needed a vessel.
Thousands of years ago grapes were first crushed in shallow troughs, fermented in large clay urns, then stored or transported in slender amphorae or even animal skins. Early wine containers for were highly practical, typically made of clay, and function trumped form. Clay was used as a wine vessel long before wood, and while being watertight (as long as the seal was good), clay was heavy, breakable and unwieldy. Unlike wood, which was the next logical progression.
Due to the perishable nature of wood, the evolution of the barrel is not easy to pinpoint. The wooden cask seems to have been first used by the ancient Mesopotamians, fashioned from palm trees. Romans were then the first to use oak (discovered as Roman legions pushed north and west from Italy), a tighter grained wood that had the advantage of bending more easily than palm, and weighed far less than clay. Eventually, the flavours that wine absorbed from oak and the mellowing effects of slow oxygen contact were deemed beneficial, and the cask became not just a vessel for transport, but a means of enhancing wine.
Today, two millennia after the oak barrel became widespread, vessels used to ferment, age and store wine are now made of many materials, they come in diverse sizes, and it should be noted, they cost little or a fortune. But in general wine vessels fall into three camps:
- vessels that allow contact with oxygen
- vessels that prevent contact with oxygen
- vessels that allow contact with oxygen and also add beneficial aromas and flavours to wine
Here’s a quick rundown of vessel choices winemakers enjoy, and their primary benefits. As always in life, what’s old is new again, and in addition to the many other innovations, clay and concrete have made a comeback.
First, a few matters of size and purpose. Vessels can be very small (like the foot stool-sized quarter casks that some whiskies are aged in) or enormous (imagine 2.6 million litres) stainless steel tanks. The material can be old (one of the oldest continually used oak barrels dates from the late 1700s, and a 400 year old giant barrel was recently repaired and refilled), or brand spanking new, such as a 225 litre oak barrique. In general, oxygen is the enemy of wine, but small amounts of exposure (such as the miniscule amount that is transferred through wood, clay and concrete) can be beneficial. Temperature control is also part of the vessel equation. Cost is highy variable, and plays a role in winemaker choice. Many wines are fermented in a particular vessel, and then aged or matured in a differing one. For example, a Chardonnay wine may be fermented in a steel tank, and then aged in a small, new oak barrel. There are implications for every choice, making the selection of vessels one of the most important of all winemaker decisions.
Vessels that do not add flavour to wine, but allow limited contact with oxygen
Clay amphorae - clay is a fine-grained natural rock or soil material that includes organic matter and trace oxides. Clay is malleable due to its water content and becomes hard upon drying or firing. Grain size varies, as does colour and water impermeability, but the dominant advantage of clay in a historical sense was wide availability. Amphorae offer two to three times greater oxygen transfer rates compared to barrels. Amphorae can be lined with beeswax to seal, but most agree this adds a subtle flavour to the wine. Just to clarify some naming issues: terracotta is a type of clay, and ceramic refers to clay that has been fired.
Used wooden barrels will not infuse wine with flavours, but the slightly porous grain will allow slow oxygen transfer into wine. When is a barrel considered used? It depends on things like origin, thickness and seasoning of the wood, but generally by the fourth or fifth use, the wood flavours have diminished rendering the barrel largely neutral.
Concrete vessels are both old and new in wine making. Concrete is inert and flavourless, provides ease of temperature control, and offers straightforward cleaning. Concrete also allows oxygen transfer, but about half as much as a European oak barrel. Shape matters: the egg shape encourages movement of the fermenting wine, and enhances texture-building lees contact. Tanks can be made in many shapes and sizes, and include cooling systems within them. The origin of the concrete can play a role in the degree of breathability and cost. Cement and concrete are not the same thing - cement’s mass is only about 15% of the total mass of concrete, and concrete is stronger and less porous than cement alone.
Vessels that allow aroma and flavour transfer and also provide limited contact with oxygen
New or slightly used wooden barrels can contribute attractive aromas and flavours to wine. Oak contains lignins and lactones and, because the inside of barrels are toasted to varying degrees, smoke and toasty characters also. European oak and American oak are widely used and each has distinctly different flavour profiles, grain size and oxygen transfer rates.
Vessels that prevent oxygen contact and add no aroma or flavour
Stainless Steel tanks provide a completely inert fermentation or ageing environment for wine. There is no flavour transfer at all, the tanks can be easily temperature controlled, and they can be easily fitted with devices to stir lees or maximise extraction. Steel tanks are typically sealed to inhibit oxygen contact. Stainless steel is often the vessel of choice for aromatic grapes like Gewurztraminer or Sauvignon Blanc, as the focus is kept on the desirable floral and fruit characters.
Lined concrete tanks were widely used before the development and adoption of the more easily maintained stainless steel tank. Epoxy or glass or wax prevented the direct contact of wine and concrete, so there is no oxygen transfer, assuming that the cover was also airtight. These tanks are seldom used these days.
The Vessel was selected as the topic for the Fifth Annual Grape Debate, hosted by Alumni UBC on Thursday, January 26, 2016. DJ moderated the lively discussion between Mission Hill’s Darryl Brooker, Okanagan Crush Pad’s Christine Coletta, Sandhill’s Howard Soon, Sid Cross, Tony Holler, David Scholefield, and several other knowledge wine folks. Get more information here.