Oval Wine Tanks
June 2025
Oak wine casks (Photo: Tara Wolff)
Having a brother and sister-in-law who enjoy food and wine is great. She, being an excellent photographer, emails me photos of what they have experienced and seen. Recently, they visited wineries in the eastern French wine region of Châteauneuf-du-Pape, along the southern Rhone River. Here is a photo she sent of six elegant oval oak casks sitting quietly in one of the winery caves.
New oval wine casks with stainless steel fittings
Look at the casks in these photos closely. Besides their elegant stature, the artisanry is amazing. For example, in a wine or whiskey barrel, the angles on the staves vary, but in a direct ratio to the width of the stave. In an oval, the angle changes not only depending upon the stave width, but its position, whether it is on the top or bottom or on one of the sides.
Further, given the larger sizes of many of the casks, the staves can’t be bent over a fire; they must individually steam heated. Once the wood is sufficiently flexible, it is placed in a template to set it in the correct curvature. Since steaming provides a different organoleptic profile from bending wood over an open fire, some are subsequently assembled without the ends and set over small fires to ‘toast’ the oak, a process that can take a full day.
When all the pieces are ready to assemble, the bottom staves are placed within two cradle-like bases. The cask’s ends are then set within the croze of those staves, propped up to hold them erect as the remainer of the staves are positioned, adding first the sides and working up to the top. All these steps in their fabrication, plus sizing the hoops and cutting a door, are time-consuming, adding to their costs.
Both an oval cask and a wooden tank can hold more wine per volume of space than a barrel. Thus, they are used to store larger quantities. But an advantage of the ovals versus round tanks is their efficient use of the space, especially in caves with low ceilings. However, in both shapes, the larger volume, as compared with barrels, reduces the wood contact as the surface area for the wine to interact with the wood is minimized.
Another advantage of an oval cask is that as the wine evaporates, the surface area at its top becomes only very slowly larger, like a barrel. Whereas in a flat-topped wooden tank, once the wine level drops below the top, suddenly a huge surface area is exposed, creating the potential for oxidization. If the tank is not topped up frequently, the cover can dry out, allowing air to enter.
Another advantage is that they look really cool in a wine cellar.
Oval casks are and have been crafted in a range of sizes and uses. Some, in the one- to five-litre range were built as elaborate displays to be set upon a bar or restaurant cabinet for dispensing port, sherry, cognac or other spirits, or cordials. Others are in the 200- to 400-litre range to mimic barrels in their ageing characteristics. Typically, the ones now used in wineries are in the larger 1000- to 5000-litre range (as shown in the photos above).
One of the largest oval casks in the world is in Germany, set deep within the cellar of the Heildelberg Castle; the Heildelberg Tun. Now in its fourth iteration, this one having been built in 1751 because the previous ones were burned or otherwise destroyed, it could hold over 200,000 litres. It is so large that a dance floor was once built atop of it. No longer used for wine, it functions as a tourist attraction within the castle.
The Heidelberg Tun
Many oak wine casks are initially utilized to ferment and age white wine. The tartrate build up is minimum. But when they are shifted to ageing red wine, despite the sloping sides, the build up after several vintages can be substantial. Early in my career as a cooper I was tasked to clean the interior of several red wine casks.
To clean them, the first problem is just getting into the tank. The door, or manway, is typically a small, vertical slot (see photos). One must put your arms and head in first then turn sideways to slither the rest of your body in. And you are not turning on your side on the floor, but a foot or two above, which provides no purchase to make the twist. Of course, don’t even try to get in one if you are claustrophobic.
Then once inside, moving around is difficult with the sloping sides.
One cask I entered hadn’t been sufficiently aired, it still stank of sulphur gas. My dust mask didn’t help, nor did the fan outside.
Once in a tank, I used a power grinder to sand away the tartrates. I should say, I attempted to use the grinder. Dust quickly fills the cask. And no matter the breathing aides or dusk masks, it’s a difficult job.
One other note; the flat surface of a cask heads often becomes a palette for art; some being carved, others painted. The Beringer Winery in St. Helena, Napa Valley, California was started by German brothers, Jacob and Fredrick. Their first vintage in 1876, and once established, the brothers imported four of the carved oval casks of German oak to enhance their wines and embellish their winery. Over the years, their cellarmen must have decided that painting and varnishing the casks improved their appearance. However, by the 1980’s the casks were too old to use but at least could enhance the ambiance of the cellar once the details of the carving were re-exposed. The Beringer management asked my colleagues and I to clean them.
Stripping away the multiple coatings of varnish was laborious. At least we didn’t have to get inside the casks. One of the casks had the ornate carving of a cherub dancing beneath a grape trellis. After days of scrubbing, a detailed highlight was revealed, the fingernails of the cherub’s hand, showing the finesse and extremely fine craftsmanship of those carvers.