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First published in the February/March 2013 edition of Classic Wine magazine

When it comes to wine cellars, gravity flow is a common catchphrase, with most wineries proclaiming to use gravity flow in the making of wine. But what does it mean? And what does it do for winemaking?

Gravity n. The force that attracts a body to the centre of the earth or other celestial body
Flow v. & n. Glide along as a stream

In gravity-flow winemaking, gravity is used for some or all of the winemaking processes in place of pumps and other mechanical tools. The cellars are made up of two or more levels to allow gravity to play its role.  When building a gravity-flow cellar, winemakers have the options of building up, down or into a slope (if the terrain allows it), or a combination of these. The first two options each pose a similar challenge; either getting the grapes to the top of the building to start the process, or getting the wine to the surface at the end of the process. Many winemakers resolve that challenge by using pumps, although ski-lifts, cranes and industrial elevators are options, if cost allows it.

When considering the drivers behind building a gravity-flow cellar, the possibilities were: environmental considerations, cost-saving, quality winemaking and marketing. On visiting a few of the cellars, it was very soon apparent that cost-saving could not be a driver; even the smaller gravity-flow cellars are engineering and architectural feats, each one unique, beautiful and mostly high-tech. Using gravity is more environmentally friendly than using pumps, but for many, that factor alone would not warrant the expense of building a dedicated gravity-flow cellar. That left two possible motivators: quality and marketing, and the question as to which played the bigger role.

The answer turned out to be complex and unquantifiable. There is no standard by which a wine cellar can claim to be a gravity-flow cellar. By placing a press on a table with a bucket beneath it, one can claim to be using gravity to make wine. Therefore it is possible that some cellars claim to use gravity flow for marketing purposes, to cash in on the consumers’ perceptions of higher quality and environmental friendliness. But what of the bigger and wealthier producers, who spend large fortunes on installing state-of-the-art gravity-flow cellars? Many of those producers already have reputations that transcend the need for marketing hype. It was time to visit some gravity-flow wineries and speak to the winemakers themselves.

Bilton Cellar 1

Bilton cellar

Rudi De Wet, former winemaker at Bilton Wines, presided over a cellar consisting of two levels, designed by Herbert Fueg engineers. The upper level is constructed out of stainless steel, as are the stairwells and girders. The concrete floor is extremely thick, as it needs to support the weight of the fermentation tanks that are positioned on a steel lattice on the upper level. The grapes are pressed at ground level. The must is then pumped through a mash cooler to the tanks at the top. The liquid in the tanks can be released downwards via gravity for subsequent pressings or into casks for barrel fermentation or maturation.

Rudi outlined some of the pros and cons of a gravity-flow cellar.  On the positive side, the process is gentle, and causes less oxidation than would occur using heavy-duty pumps. The grapes experience less friction throughout the process, leading to less ‘green’ wine. Electricity costs are lower as the use of pumps is minimal. On the negative side, Rudi explained that gravity-flow cellars are costly to build, and from a practical point of view, the design of the cellar makes for frequent trips up and down the stairs, which during the height of harvesting can be fairly slippery.

Charl Theron, an oenology adviser, agreed that gravity-flow was all about softer handling of grapes. When asked about the fact that some wineries need to use pumps to get the grapes up to the crushers, and whether that did not cancel out the subsequent gains from the gravity-flow processes, Charl replied that modern pumps are far better and softer than they used to be, and typically winemakers will use a combination of gravity and pumps, depending on what makes the most sense in practical and economic terms.

Antonij Rupert, Terra del Capo

Antonij Rupert, Terra del Capo

The next visit was to the exquisite Antonij Rupert estate in Franschhoek. The state-of-the-art cellar is called Terra del Capo (Land of the Cape) and from outside resembles a Martello Tower, set against the magnificent backdrop of vines and the Groot Drakenstein mountains. The cellar, designed by Johan Wessels, an architect and structural engineer who specialises in winery construction, is built onto and into a slope, and is therefore easily accessible from both the top and bottom levels. Grapes are easily transported to the top entrance where the sorting tables and press are.  The wine is bottled on the lowest level, and can be collected from the lower entrance.

The impressive interior of Terra del Capo incorporates both a central spiral stairwell and a lift. The cellar design was inspired by the mechanics of a watch wheel; above the second level, there is a 32-ton cast iron revolving mechanism that rotates gondolas above a circle of large alternately arranged wooden and stainless steel fermentation tanks. The grapes are fed into the gondolas from the top floor and then rotated above the tanks, into which they are released. Oak casks are filled with wine at the top level of the cellar and lowered gently through manholes using an overhead crane and clamp to the lowest level, which houses the glass-partitioned maturation cellar.

Antonij Rupert - Dawie Botha

Antonij Rupert – Dawie Botha

Dawie Botha, winemaker at Antonij Rupert, said that as a winemaker, it was wonderful to work with gravity. The entire process was gentler and more natural. He explained that gravity was just one aspect of the art of quality winemaking. In his opinion using gravity makes for better wine, but it is one tool of many that a winemaker can choose from, and cannot be divorced from the whole process. It is an expensive way of making wine, and a slow one, and at Antonij Rupert gravity flow is used for their best wines.

Vergelegen cellar

Vergelegen cellar

Vergelegen built the first formal gravity-flow cellar in South Africa in 1991. Designed by architect Patrick Dillon Erbe, at the time it was amongst the first custom-designed gravity-flow cellars in the world. For André van Rensburg, Vergelegen’s winemaker, much of the value of the design lies in the environmental benefits and aesthetics. The winery is 30 meters high, 20 meters of which is under ground. The roof is covered in grass and ponds, both of which serve to cool the building interior. The layers underground are extremely well insulated – in winter remaining up to 10 degrees higher than the outside temperature and in summer up to 10 degrees lower. The cellar is extremely beautiful and attracts visitors from all over the world, featuring in several coffee table publications on architectural design.

André said that the idea that gravity-flow leads to better wines is based on gut feel and cannot be scientifically proven, in the same way that many winemakers believe that older vines make better wines. He agreed that some aspects of gravity-flow wine making are expensive and impractical, and said that the process is too slow to handle the entire 35 tons processed at Vergelegen per day. Like most other wineries, the process is used for the premium wines. André agreed with Dawie Botha from Antonij Rupert that gravity-flow was simply one aspect of the winemaking process – one tool in the winemakers toolkit.

Lourensford cellar

Lourensford cellar

At Lourensford there is a large and impressive gravity-flow cellar that is based on the design of Abadia Retuerta winery in Spain. Abadia Retuerta was designed by French winemaker Pascal Delbeck in 1996, and is considered by some to be one of the most advanced wineries in Europe. According to winemaker, Hannes Nel, the Lourensford cellar was designed by ZJ engineers, who visited Abadia Retuerta to better inform their design. Three of the levels of the cellar are above ground with one level below ground. Hannes said that a significant advantage of the design is that large volumes of grape-must can be released from the fermentation tanks via a butterfly valve into holding tanks below, and then pumped back up and into the tanks to break up the cap using pump-overs. Hannes said that using pumps for certain aspects of the process does not detract from quality, as pumps are so much more sophisticated than they used to be. It is practical to use a combination of pumps and gravity flow in ways that make sense to the winemaker.

Chris Joubert, cellar master at Lourensford, reiterated the sentiments of the other winemakers – gravity-flow is one winemaking method among many. He said that it is possible to make quality wine with and without gravity flow, but gravity flow is gentle and enjoyable to work with, saying that ‘passion comes from the heart, and winemaking comes from the heart’. Chris demonstrated the use of a remote-controlled pulley to lift and move a five-ton fermentation tank from an upper level of the cellar to a lower level, which it accomplished with grace and ease.

Chris provided his own take on gravity: ‘At Romanée-Conti, when royalty needed to be served wine, the winemaker sat on the barrel decanting wine with a pipe. By candlelight, the winemaker stamped his seal of approval on the wine and handed it to the royals. That is the ultimate gravity.’

Palmaz, Nappa Valley - Fermentation dome

Palmaz, Nappa Valley – Fermentation dome

There are many international examples of gravity-flow cellars and many passionate proponents of the process. A striking example is the 15-storey-high gravity-flow winery Palmaz, in Napa Valley, California. The winery is built on four levels into the foothills of Mount George, all underground. According to Dr Julio Palmaz, who played a key role in the cellar’s design, ‘Gravity is the oldest and gentlest way to move wine. It avoids disruption of the delicate molecules, preserving the wine’s complexity and structure.’

Palmaz vineyards:

  •   The winery spans the equivalent height of a   15-story building.
  •   At 22 meters in diameter and 16.5 meters in   height, the fermentation dome is one of the world’s largest underground reinforced   structures that is built into soft terrain.
  •   The surrounding earth keeps the ambient   temperatures at a constant 15.5 degrees Celsius and the humidity at 88%.
  •   The winemaking process begins at the top of   the cellar and continues downward through each stage.
  •   The massive carousel of 24 moveable stainless   steel fermentation tanks is the only one of its kind in the world.

Dr Palmaz owns and runs the winery along with his wife Amalia, and children Florencia and Christian. I asked Florencia whether gravity-flow wines taste better, and she responded ‘I am not sure you can say with certainty that they taste better, but I think that they feel better. The tannins tend to express themselves with a finer grain when handled gently.’

For Florencia one of the pros behind gravity-flow winemaking is that all movements have to be carefully planned, leading to precise winemaking. She added that the same factor was sometimes a con, as a high degree of organisation was required and no parts of the process could be rushed. When asked whether pumps were used anywhere in the process, Florencia replied ‘Because we are a Cabernet house, we have chosen to use pumps for pump-overs during the early fermentation to ensure sufficient cap extraction. We have refined our understanding of gravity flow – there are moments to be rough and moments to be gentle. The early stage of fermentation is the only time we encourage a little roughness, to guarantee a wine of full tannin and colour extraction. If we made a lighter-bodied wine like Pinot, I would rethink this protocol.’

Florencia advised anyone who is planning to design and build a gravity-flow cellar to make the distances that the wine travelled as short as possible, as even short downhill flows can be turbulent if not checked with valves. With regard to energy savings, she reiterated what André van Rensberg from Vergelegen had said, saying ‘the choice to build underground is what contributes to a real energy saving. The elimination of pumps is a small saving in comparison to passive temperature control of the cellar.’ When asked whether she would change anything if she designed the cellar again from scratch, Florencia said that she would add a few small test-batch-sized fermenters to the carousel. All Palmaz’s small test batches are fermented in T-bins, which makes it difficult to ascertain whether wines differ due to the vineyard test differences or the different manner of fermentation.

It seems that gravity-flow winemaking is a worthy process, with quality benefits that are widely held to exist but difficult to quantify. Anyone that takes the trouble and expense to implement such high-tech and attractive wine-making facilities most likely takes the same trouble with their winemaking. Gravity-flow cellars are sexy. Such sexy cellars must surely produce sexy wine. And they do.