(SFChronicle) - It’s hard to imagine Joel Peterson has anything to prove. Starting in the 1970s, the onetime bacteriologist began building Ravenswood Winery from an itinerant side project — the wines were once aged in a former toilet-seat shop — into a household name.

Indeed, it’s likely that Ravenswood, and Peterson, was what got you drinking Zinfandel in the first place. Red Zinfandel, that is. Its memorable tagline, “No Wimpy Wines,” was a battle cry against sweet White Zin.

More seriously, Ravenswood’s single-vineyard Zins, crafted from old vineyards like Teldeschi and Old Hill Ranch, paved a path for the modern fascination with serious Zinfandel — and the success of wineries like Turley Wine Cellars, Carlisle and Bedrock, the last run by Peterson’s son Morgan Twain-Peterson (one of The Chronicle’s 2015 winemakers of the year). Along with Ridge’s Paul Draper, Peterson and his wines proposed a different path for Zinfandel: It could be serious, age-worthy, a framework for California terroir. And even after he sold his beloved project to Constellation Brands in 2001, he stayed on well past his two-year contract. Only this year, finally, is he planning to relinquish his role as founding winemaker.

Now, in other words, would be the time to kick back for a chill Sonoma summer and spend more time with his wife, Mady Deininger, and their 17-year-old son Galen Peterson.

No way. Peterson, 69, is preparing to round the game board one more time. His new label, appropriately dubbed Once & Future, will debut in late March with two wines: a Zinfandel from the historic Bedrock site in Glen Ellen, owned by his family, and a Petite Sirah from Calistoga, in northern Napa Valley. Both are an attempt to recapture Peterson’s early days.

“I said, ‘Can you go back and can you rebuild the vision you had?’” he recalls. “Can you rebuild the ideal of making small-lot wines in a really traditional way, getting your hands really dirty? Can you in fact make that work?”

In an obvious way? Sure. This should be a breeze for Peterson, and certainly his place in wine history is more than secure; his old tool for punching down grapes is in the Smithsonian.

In a less obvious way, Once & Future is a curious sort of second chance: a calculated bet on the charms of small-time winemaking, and a visible distancing from the business pressures that pushed Peterson to grow Ravenswood into a swaggering Zin giant. That might be why Peterson has been quoting Kierkegaard lately: “Life must be lived forwards but can only be understood backwards.”

Ravenswood, and the familiar raven label, are such a familiar sight on supermarket shelves that it’s hard to imagine the winery in its original form. In the 1970s, it embodied the sort of cultish, garage-band ethos that California wine is once again exalting. Peterson’s debut 1976 Zinfandel was released in 1979 for the then-outrageous price of $7.50. The early years were slow; he only quit his day job, as a clinician at Sonoma Valley Hospital, in 1992.

“When I started Ravenswood, I had a whole different vision of what I wanted to do,” he says — a modest project, perhaps 6,000 cases per year. He would make wine in small lots, with some New World twists on what otherwise was traditional European winemaking.

The approach was familiar to the young Peterson, who grew up tasting Bordeaux and Burgundy collected by his grandfather, who ran San Francisco’s Vintners Club. It was the same approach imparted by Peterson’s winemaking mentor, Joseph Swan: French oak barrels, indigenous yeasts, cellar work by hand. Early Ravenswood wines were fermented in the sort of old-fashioned open wooden vessels — although made of redwood, not oak — that subtly soften and freshen young wines.

In the 1980s, when Peterson introduced his single-vineyard wines, he again set benchmarks for Zinfandel, and highlighted some of the state’s oldest, largely forgotten vines, which otherwise were at risk of being yanked out. But Ravenswood kept growing, propelled by its cheap, easy-drinking Vintners Blend red. By the time of its sale to Constellation, the world’s largest wine firm, in 2001, it was making 440,000 cases. (Production subsequently exceeded 1 million cases.)