Franken Casks the First Stone

Muschelkalk, or shell limestone, is a fine-grained, grayish-white stone with a smooth surface, formed over eons, as the shells of millions of sea creatures collected and were compressed until they crumbled and fused into stone. Roughly 240 million years ago, wide stretches of central Europe lay under an ancient ocean’s waters. The shallow sea of the Germanic Basin was home to a variety of marine life. The shell limestone that resulted now represents a shared identity for vintners in the heart of Franken — and for Silvaner, their much-loved grape variety. In fact, the stone is said to add a delicately fruity, charming, and accessible note to the wine.

A rocky revolution begins in Franken

The question of how to bring the wine even closer to its stony influence has been on the minds of winegrowers for a long time. “I asked myself what could bring the wine even more closely into contact with the shell limestone,” remembers winery and hotel owner Jochen Meintzinger of Frickenhausen am Main. “So I laid cleaned shell limestone into a stainless steel tank and filled grape juice around it. It made no appreciable difference, which I interpreted to mean that the added-stones approach didn’t make much sense.” Despite the sobering results, the Frickenhausen native wasn’t ready to give up.

And as so often is the case in life, coincidence lent a helping hand when Meintzinger later struck up a conversation with stonemason Alexander Dittmeier from the Franconian town of Gemünden. Dittmeier had already built water troughs from shell limestone. His advice: Why not build a vat high enough for wine to mature in it? Granite tanks, he posited, were already in use, so there was no reason it couldn’t work with shell limestone, too. 

“Sandstone is what we most frequently process as a raw material. But we had some experience with shell limestone. Typically as a flooring for outdoor use or as a watering trough, never as a wine tank,” he laughs. Meintzinger ordered three tanks from the Dittmeiers. And because the wine world is small, and Franken all the more so, word got around.

Cutting-edge science in Franken’s wine scene

Bavaria’s State Institute for Viticulture and Horticulture (LWG) in Veitshöchheim was taken with the idea of a shell limestone tank and decided to experiment with a conical stone trough — also produced by Dittmeier’s company. Felix Baumann, deputy department director for oenological experiments, reports: “The idea came from my colleague Johannes Burkert. But we were clear from the start that you couldn’t just fill them with wine. Limestone reacts to tartaric acid, producing CO2 and de-acidifying the wine at the same time. That’s precisely what we wanted to avoid. So we coated the inside of the tank with a paste of tartaric acid, then installed an acidic medium. Once we reached the point where the pH value was no longer rising, I could use the tank for wine — both for fermentation and maturation.” 

LWG researchers still had to deal with a second issue: The first test vessel ultimately proved too porous. “When the wine makes its way into those porous layers,” Baumann explains, “it doesn’t take long before it starts stinking of ammonia.” The researchers posed a new request to Dittmeier: Build a tank of flawless shell limestone, then coat it with a paste of tartaric acid until a stable layer of tartar forms. 

“Interestingly,” Dittmeier says, “there is apparently just one single place in Franken that offers this ideal shell limestone, known as Quaderkalk: the quarries in Kirchheim south of Würzburg.” Meintzinger, whose tanks were already in use, confirms: “I’d very gladly have taken a tank directly from the quarry here in Frickenhausen, but the stone is simply too crumbly. That looks really lovely when it comes to things like facade slabs with a bit of grain, but tanks are about functionality.”

Muschelkalk madness: how Franken winemakers got stoned

Once the LWG received its new Dittmeier tank, the task then shifted to producing a wine that the researchers could track as it developed, and then ultimately stage a workshop for winegrowers to let them try it. One of the invited winemakers was Markus Schmachtenberger from Randersacker on the Main. “At that LWG event, we tasted wines from the same batch that had been raised in four different vessels: steel, wood, concrete egg, and shell limestone tank.”

“I asked myself what could bring the wine even more closely into contact with the shell limestone.”

— Jochen Meintzinger

Baumann recalls that the blind test for the shell limestone tank wasn’t particularly positive. Most of the wine tasted acidic and bitter, while the wooden cask resulted in wine that was both softer and richer in body. Yet Schmachtenberger came away with a completely different impression: “It knocked my socks off,” he says. “The other wines were too rich for me. But the one from shell limestone was lean, deep, with a length intended for cellaring, all of which fits our estate style unbelievably well.” He immediately asked where he could get a tank like that.

Soon a third vintner in Franken was bitten by the shell limestone bug, Christian Reiss from Würzburg. Like Meintzinger and Schmachtenberger, Reiss’ family has been producing wine at its estate for centuries. His road to the shell limestone tank, however, was more winding. “A producer of granite tanks from the Bayerischer Wald approached us to ask if we’d be interested in giving his product a try. So we leased his tank for a season. We’d already experimented with clay amphora, but a stone tank is something else entirely.” One year later, the feedback they received on the granite tank wines was largely positive, but people also asked why they weren’t using local stone. Reiss put one and one together — and bought a shell limestone tank from Dittmeier the following year.

The rocky road to innovation 

When Meintzinger introduced his limestone tanks to the market, as the first to do so, he encountered unpleasant resistance. The granite tank producer claimed that it held a design patent for stone tanks; that the patent covered tanks made from granite, not shell limestone, was irrelevant. “We had to go to court over the issue because he sued me to cease and desist,” Meintzinger recalls. In his view, the tank wasn’t just made from a different material than granite. It was different in every way. The courts ultimately agreed. “The granite tank had a stone cover, while my shell limestone tank is open-topped, with a floating cap of stainless steel so that it’s always full.” The whole affair left a bad taste in Meintzinger’s mouth. “Since they lost the legal battle, we’ve been able to use and advertise our tanks without an issue.”

All three vintners today use their shell limestone tanks to raise their own special Silvaners. “The wine is wonderful,” Meintzinger says, but one shouldn’t imagine that its taste is especially mineral —an observation shared by Baumann from the LWG. “We’ve run chemical analyses and have not identified any substantial transfer from the shell limestone into the wine. Nevertheless, we continue to use our own shell limestone barrel for individual batches because the resulting wine is really special, albeit for a different reason.”

So what could this reason be? “It’s the way fermentation works. The tank has extremely thick walls and is as cold as the cellar at the beginning. So the must starts fermenting cool and very slow.” After a certain period, however, that tableau reverses: The warmth of fermentation heats the stone more sustainably, bringing a certain storminess to the process that ends only once the must has been fully fermented — more reliably than in other vessels. This outcome fits the style of the three winegrowers, all of whom works with spontaneous fermentation.

Stone-aged Silvaner is making modern waves

After four years and plenty of experience, Christian Reiss developed a road map for raising Silvaner in a shell limestone tank in accordance with his expectations. “First, we harvest the grapes based on their acidity levels. We want to avoid malolactic fermentation because that doesn’t fit our style at all. We then whole cluster press, allowing the wine to ferment spontaneously and settle without filtration. My goal is to create a wine that has a mineral, saline, cool profile, because that’s what you expect from a Silvaner raised in stone.”

Schmachtenberger puts only his absolute best fruit into the shell limestone tank. “It reliably ferments fully and shows tremendous finesse. We always reserve a little bit of that for blending with the Großes Gewächs.” The Silvaner raised in shell limestone is also called “Quaderkalk im Quadrat.” “Grown in Quaderkalk, raised in Quaderkalk. The story tells itself,” he says, noting that Franconian Quaderkalk can be found in famous structures such as Grand Central Terminal in New York. 

Ask the vintners for their bottom line on this subject and all are full of praise. “Tastes totally pure,” Reiss gushes. “That precise style,” says Schmachtenberger enthusiastically. And Meintzinger, the pioneer, links the joys to the practical benefits as well. “Because of the hotel, we naturally offer a lot of cellar tours. And once the guests see the shell limestone tank in the cellar and I explain the background to them, the wine sells twice as well.”

Dittmeier has sold an additional shell limestone tank to an estate in Switzerland. At Weinmanufaktur Brunner in the northern Swiss town of Aargau, the tank is used to produce a delicate Riesling. At €6,000, however, the limestone tank is unlikely to turn into a bestseller. Beyond that, there are legendary stories about transporting the 1,200-kg vessel into narrow old cellars. But the three vintners just smile when asked. As far as they’re concerned, these vessels — and wines — speak for themselves.

Set in Stone: three Silvaners to taste

Weingut Reiss, Würzburg: Silvaner aus dem Muschelkalkfass 2022. Würzburger Pfaffenberg, 12% abv. 

Astoundingly spicy/earthy on the nose, heading toward rye bread. Edgy, citric, and fresh on the dry and linear palate. Easy-drinking with a firm core and grand cru concentration.

Weingut Markus Schmachtenberger, Randersacker: Silvaner Quaderkalk im Quadrat 2022. Randersackerer Sonnenstuhl, 14% abv.

Tremendously fruit-driven on the nose, with vineyard peach and a bit of orange peel, all characteristic for the Randersacker sites. An elegant and nuanced palate marked by grapefruit, Meyer lemon, and in particular a wonderful, silken texture. The high alcohol is beautifully integrated into the acid, fruit, and stony salinity. A supremely elegant wine.

Weingut Meintzinger, Frickenhausen: Silvaner Noch Fragen? 2018. Frickenhäuser Kapellenberg, 13.5% abv.

Darker than the other two in the glass with ripe notes of citrus zest, quince, and yellow mango. On the palate, it is fully fermented with a fine, persistent acidity, and silken texture. Pure with the first hints of bottle maturity. Perfect now for freshwater fish such as pikeperch.

translated by weinstory.de