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Harvest is in full swing and fermentations are bubbling throughout the valley. But have you ever wondered about all the different shapes, sizes and types of tanks, bins, barrels and even the odd concrete egg that are being used in the fermentation process?

In early Roman times, clay amphorae were utilized to ferment wine. Later, skilled winemakers of the day began burying these vessels in the earth (leaving the top above ground) for more even temperatures during this critical process. Open limestone cubicles followed, evolving into structures made of stone and later concrete, which are still used today.

As history progressed, the winemaker sought more control over fermentation so large wooden ovals and uprights were brought indoors. The advent of small barrels added a different touch and eventually stainless steel became popular.

Over the years, I’ve visited countless wineries both here and abroad and continue to marvel at the sheer scope of vessels used, each with its own story as to how it is the “best” or “most suited” to a particular wine. So, for a better understanding, I spoke with Brooks Painter, director of winemaking for Sattui Family Wines and San Francisco International Wine Competition 2013 Winemaker of the Year.

After World War II, stainless tanks (with both open and closed tops) were developed and heralded as the perfect fermentation tool since temperatures could be efficiently controlled with glycol-filled jackets and easily cleaned after the process was complete. The tanks were originally developed in California where Robert Mondavi saw their value and became an avid proponent of the technology. In a short time, they became the norm domestically and eventually found a home in Europe as well.

Today, stainless steel tanks are found in virtually every wine producing area of the world and come in a wide variety of shapes and sizes complete with a multitude of precise controls for fermentation. More recently, horizontal rotating tanks have become available to avoid punching (submerging) the cap down or pumping the juice over to extract color, tannin and flavor. Aside from fermentation, steel tanks are also used to age some wines (particularly whites), and for cold stabilization and blending various barrels before bottling.

Barrel fermentation of whites (mostly chardonnay) is a long-held tradition in the old world and more recently adopted elsewhere. Here, the juice of pressed grapes goes immediately to barrel and is left to ferment either on native or inoculated yeast. The dead yeast cells (lees) are periodically stirred to add texture, flavor and character.

More recently, barrel fermentation has also been used for reds but this necessitates removal of the barrel head in order to manually punch down the cap. The process is labor intensive, expensive and only applicable to small lots.

The concrete egg (varying from 150 to 500 gallons) is perhaps the newest fermentation innovation and used principally for whites. Concrete possesses ideal insulating qualities, and the shape of the egg creates convectional currents allowing the lees to remain in suspension adding complexity and character coupled with a layer of minerality.

As Brooks said, “The multitude of vessels available today gives us added choice and flexibility for each component leading to a far better final blend encompassing the best individual characteristics of all.”

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My Sept. 6 column — “Have Rhone varietals found a new home?” — elicited comments demonstrating a broad readers’ interest in the wines but a lack of security as to what to expect from those produced in the new world.

Simon — Although I usually enjoy the subtle nuances of Rhone syrahs, the character of most California syrahs is quite different and often off-putting to me. Why are they so different?

Syrah was one of the earliest Rhone varietals to gain popularity in California and for years went stylistically array as winemakers searched for what they perceived as wines better suited to the domestic palate and often planted for yield rather than quality. The wines of the Northern Rhone are typically more focused and terroir driven. Today, dedicated California winemakers have returned to more traditional styles and beautiful examples are coming to market.

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Allen Balik, a Napa resident, has been a wine collector, consultant, author, fundraiser and enthusiast for more than 30 years.