Cracking the Code of Concrete Eggs

“Furthermore, I consider Carthage must be destroyed.”

A friend once crafted a wine for his Bachelor's thesis at Princeton University, adding marble dust from his mom's bathroom renovation, a touch of powdered resin, and a liberal sprinkling of sea salt. Let's just say it wasn’t your Domaine Romanée-Conti, but hey, he aced his thesis.

If you're still trying to guess the flavor profile of this avant-garde, marble-infused concoction, there's a historical twist that might interest you. While unconventional in taste and appearance, this wine was all the rage 2,000 years ago, from Rome to Athens. The Petrus of the ancients.

Inspired by none other than Cato the Elder, a farmer, soldier, and politician who was just as famous for concluding his speeches with “Furthermore, I consider Carthage must be destroyed,” as he was for authoring Rome’s first Latin history book. His writings not only chronicled Roman life but also detailed ancient agricultural and winemaking practices in his guide, De Agri Cultura (Roman Farming for Dummies), the very inspiration for my friend's thesis and marble dust alcohol.

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This guide reads more like a Reddit thread than an actual manual. It’s got everything from using old seawater and vinegar to spicing things up by mixing in a few odd ingredients that, as my Princeton friend discovered, tasted something akin to alcoholic Gatorade.

While Cato didn't have the luxury of French barrels for aging his wine, he did employ the use of earthenware dolia, which he buried underground for aging, but not before lining the walls with pine resin. The resin would gradually dissolve into the wine, supposedly helping it taste more ‘aged’.

What are Concrete Eggs

Ovular in appearance and sometimes resembling an egg, these earthenware vessels were a popular tool not only in winemaking but also in the production of olive oil and the transport of grains across the Mediterranean (as confirmed by the numerous shipwrecks containing fragments and fully intact dolia).

Jumping to 2024, the Dolium is making a comeback quicker than 1990s mom jeans. More colloquially known as concrete egg fermenters, these new-age dolia are said to possess numerous benefits for the final wine, ranging from infusing vibrancy and freshness to imparting a mineral character and even bolstering the weight and complexity of both red and white wines. I'm all in; however, the supposed science behind these Humpty Dumpty vessels relies heavily on anecdotal evidence rather than ‘concrete’ data.

What do Concrete Eggs Allegedly Add to Wine?

The Vortex Thing:

The most popular claim is the egg's unique shape helps to create a natural current or ‘vortex’ during cellaring and fermentation. As fermentation begins, the wine will undergo a rolling motion facilitated by the formation of heat and carbon dioxide produced by the yeast. As warmer liquid rises, yeast and other particulates are carried upward in this ‘convection current’. As the liquid rises, however, it begins cooling, causing solids and other particulates to drop along the curved edges of the vessel before being caught up again in this vortex at the base of the fermenter.

To quote Finding Nemo, "You mean the swirling vortex of terror? That's it, dude.”

Even after fermentation, people claim “barometric pressure” sustains this ‘rolling’ motion, helping to keep the fine lees (yeast particles) in suspension. While manually stirring the yeast has been proven to produce more roundness in a wine's mouthfeel (explaining why your California Chardonnay feels weighty on the palate), the egg's shape doesn't naturally create this ‘rolling’ motion.

Breathing Concrete:

The second most common claim about the egg is its ability to ‘breathe’. Yes, concrete breathes. It is porous and lets oxygen in, which is great for the wine. Up to 18% of concrete's total volume consists of microscopic pores no larger in diameter than human hair! With higher-pressure air outside the egg, air is drawn through the walls to the lower-pressure inside. Barrels also possess porosity, which is known to help refine fruit flavors and transform granular, gritty tannins into pleasant, velvety textures. Microdosing wine with small amounts of oxygen is the reason your Opus One tastes so great much like how micro- (or macro) dosing makes some of your dull guests more interesting!

Imparting Minerality (Lick a Rock):

In his book Knowing and Making Wine, the late Emile Peynaud remarked that anything a wine touches will acquire the taste of said material. Wine does acquire the taste of concrete, but it presents itself as a ‘flinty’ flavor that people sometimes identify as ‘salty’ (think of Pellegrino water minus the bubbles). For those whose childhood involved tasting the gravel in your parent's backyard, you know exactly what I'm talking about.

Assessing the Impact of Concrete Egg Fermenters on Wine Quality

From Napa to New Zealand, the big question is, does it make the wine better? The adoption of concrete egg fermenters in winemaking has sparked a fascinating debate. While many producers find concrete eggs to have an enchanting impact on wine, you’ll find the egg has as many advocates as it does critics. Notable regions and producers have embraced the concrete egg for its purported benefits. 

In Bordeaux, Chris Upchurch observed a noticeable shift away from traditional wood casks towards concrete, signaling a potential transformation in winemaking practices. Similarly, Austrian vintners have adopted the egg, aging Sauvignon Blanc for 18 months on the lees before bottling. Upchurch himself makes a Sauvignon Blanc in a concrete egg that emulates the Austrian style, called the ‘Southwest Facing’. Elsewhere in the United States, the trend is mirrored by Napa wineries like Frogs Leap and Cakebread Cellars, Savia Cellars in Walla Walla, and Dancin Vineyards in Southern Oregon, which makes Barbera and Chardonnay with an egg. Even the Mitten State has wineries like Forty-Five North using dolia for making Gamay Noir and Pinot Blanc!

The highest-rated wine aged in concrete, to my knowledge, is Reustle-Prayer Rock’s  2018 Grüner Veltliner ‘Dolium’, a 95-point-rated wine awarded by the American Fine Wine Competition.

Despite the widespread use of concrete egg fermenters, the narrative is not without its detractors, and the decision to adopt this technology remains a personal one, grounded in each winemaker's personal beliefs and objectives. In an article by Seven Fifty Daily, Matthew Levy of Schramsberg in Napa was quoted saying they had discontinued using concrete eggs for sparkling wine, citing a lack of discernible differences in the final product compared to stainless steel, and inefficient use of space in the winery. 

Other complaints cite concrete as being reactive with wine, increasing the pH and making the wine less crisp, or being a highly inefficient use of space. Others opt for terracotta, which is far less cost-prohibitive and provides a similar function both in regards to porosity and minerality without compromising pH. Oregon’s Beckham Estate Vineyard, owned by a ceramicist turned winemaker, makes their own clay vessels very similar to dolia, believing ceramic imparts a more interesting profile to the wine than concrete.

The financial aspect cannot be overlooked. With increased financial pressures caused by buckling demand and oversupply in some regions, the barriers to entry prohibit many small wineries from even considering the investment. Barrels cost anywhere from $700 to $1,200 each (a hefty investment already), but a small concrete egg can run between $9,000 to $20,000... and it only goes up! Unlike barrels, concrete eggs do have an extended lifespan of 15 to 20 years, but more affordable products similar to the egg have emerged on the market. Companies like Egginox sell stainless steel alternatives, helping to reduce the elevated costs and offer a product that doesn’t weigh 1-2 tons.

Are Concrete Eggs Worth It?

However, as the industry is met with a younger generation of potential wine consumers who appear disinterested in wine, wineries need ways to differentiate themselves and offer a unique product (something that greatly influences my generation's purchasing behavior). Perhaps the egg will help fill that void. Is the concrete egg the snake oil of winemaking? No, I don’t think so. Is it the next best thing since sliced bread? I don’t think so either. But at the end of the day, winemakers and consumers alike must realize that clever marketing begins where great wine ends, with the concrete egg being more a marketing tool than a game-changing winemaking asset.

1. Cato the Elder, 234 BC – 149 BC, was a ferocious politician known for being unabashedly anti-Hellenistic (ironic given his wines were inspired by Greek recipes).