In the world of software development, where I spent many years, programmers confronted by an apparent bug in their code have been known to respond, "No, that's not a bug, it's a feature." This defense rarely works. But in the world of winemaking, there really are gray areas in which rules are made to be broken, where one winemaker's faults are another's complexities, and where "a little bit pregnant" isn't an oxymoron.

It all depends on your vantage point--and on your palate.

The two most common places where good winemakers go bad on purpose are probably in encouraging/allowing a "little bit" of Brettanomyces to add intrigue, and encouraging/allowing slightly elevated levels of volatile acidity to help lift the aromatics of a wine. These strategies, or tolerances, have their fans and their detractors, and the debates over how to handle them are pretty old hat in the industry.

But it was news to me, at least, when Greg La Follette, a Pinot Noir and Chardonnay specialist at Tandem Winery in Sonoma, Calif., spread the gospel of intentional sulfide production to a roomful of industry professionals at the Unified Wine & Grape Symposium in Sacramento, Calif., this past January. Then in March, I heard Domaine de la Terre Rouge winemaker Bill Easton defend the virtues of a little oxidation in white wines at a Rhone Rangers seminar in San Francisco. So it seemed like a good time to delve a little deeper into "faults" and the winemakers who love them.

I talked with four practitioners of not-entirely-standard winemaking: La Follette and Easton, veteran winemaker David Vergari of Vergari Wines, focused on Sonoma Pinot Noir and Napa Cabernet Sauvignon, and prominent Napa winemaker John Kongsgaard, now making Chardonnay and lots of other things at his own winery in St. Helena.

What's interesting about all four of them is the careful, methodical way they go about playing with fire. These folks are anything but sloppy in their cellar work--they know exactly what's mucking up their wines, and they have the lab reports to prove it.

Savory sulfides

The commercial wine industry probably spends more money preventing and fixing stuck fermentations--and their signature, rotten-egg aromatic companion, hydrogen sulfide--than on any other winemaking fault. The rise in harvest Brix levels has compounded the problem, giving a terrific boost to the prophylactic alcohol reduction business. But what about a fermentation that's slow on purpose, really sloooooooow, with yeasts on the edge of starvation, generating just a bit of wholesome sulfide funk?

That's one part of why Greg La Follette is fond of wild yeast fermentations, at least for certain wines and certain vineyards, and why he likes to put even his inoculated fermentations under some amount of stress. "It's like being a coach," he says. "You force your athletes to a certain level, beyond what they thought they could do, and you hope they recover, that you haven't pushed them too far over the edge."

Central to La Follette's yeast coaching is limiting the available nutrients and thus forcing the little critters to dig deeper. "First they eat the ammonia," he says, "then go to the amino acids, starting with alanine, and eventually start chopping off phenyl groups."

Along the way, assorted sulfide compounds can get produced, including mercaptans and dimethyl sulfide. At low levels, below the identification threshold, La Follette says these compounds can be a lot of fun, without getting a wine into rubber tire, cooked cabbage and skunk territory. He thinks these sulfide components are often what tasters perceive as "minerality." And besides spawning sulfide groups, struggling yeasts can give off lots of other interesting aromatics.

One place this works for La Follette year after year is his Sangiacomo Vineyard Chardonnay. That fruit and the microbes it brings into the cellar with it make for what he calls "a very feral, animale wine." The 2003 made it into a book about aphrodisiacs. One prominent wine magazine loved it, one hated it, one thought the nose was full of oak, though La Follette says it had less oak than usual, and that the critic was smelling yeast stress. In any case, the wine was hard to ignore, which is more than can be said for a lot of California Chardonnay.

La Follette describes his style of winemaking as "edgy" or "unsafe," because of the risks involved. John Kongsgaard simply calls it traditional. "If you have a non-chemically farmed vineyard, you will probably have lower natural nitrogen in the must. And if you don't add cultured yeast and don't add any or much nutrient, then you have a low nutrition cocktail. That means you have slow f ermentation. Nerds would consider that slow or sluggish; but in the 11th century, it was quite normal to finish fermentations in the spring, which gets you a different flavor profile."

Kongsgaard thinks, at least for Chardonnay, that fermentations that are slow to start and slow to finish promote vastly better mouthfeel. Among other things, natural fermentations, with their changing cast of yeasts coming and going over time, produce "wonderful sulfide groups in the aromatics: Too much of this is not interesting, but a little background rumble is very interesting."

Since winemakers of this persuasion have no interest in making wines that reek of rotten eggs, they realize that inviting wild yeasts in and keeping nutrient additions out requires intimate knowledge of what's going on in the fermenter. It's not enough to stand back and watch; you have to monitor the temperature, plate your bugs and identify them under the microscope, measure nutrient levels to make sure they aren't at zero, and know from past years how your vineyards perform. "If the yeasts find too many things wrong that they don't like," La Follette says, "they will just crash and burn."

Timely oxidation

The basic line on oxygen and winemaking is pretty well established: Make sure to have some available early so the fermentation gets done, and make sure to keep it at bay later on. There are, however, a lot of variations on those themes, some of which are more conventional than others.

La Follette and David Vergari like a little oxygen in their Chardonnays, especially early on, allowing browning and pinking to happen without getting too nervous and cleaning things up later on. (La Follette promised that if I was very good, he would someday show me the secret handshake of the Brown Juice Club that makes white wines this way.)

Vergari made the wines for Maddalena on the Central Coast for years, and in that much more mainstream environment, he would never have dared to do a wild fermentation or let loose a native malolactic or send wine to bottle unfiltered. But he's happy to take those risks--and more--with his own label. Then again, the risks are thought out: oxygen for Chardonnay: good; but oxygen for Pinot Noir is bad in his book.

Kongsgaard's plan on oxygen and Chardonnay is to expose it early and "resurrect" it later on. Slow, wild fermentation means that the wine is to some extent protected from oxygen by a layer of CO₂, which means sulfite additions can be postponed. But inevitably some soaks in, creating aldehydes, which are finally and fortunately devoured by yeast activity at the end of a renewed fermentation.

"If you oxidize a polyphenol early on," he says, "it's not there to oxidize later. Getting it done early protects against oxidation in the bottle. The wines that don't last are the ones with no exposure to oxygen early on."

The science of unsafe winemaking

Wines like the ones these winemakers produce don't just happen; they're not just examples of letting nature take her course. These wines are chaperoned at every step along the way--sniffed and tasted, tested and plated and scoped--and, where necessary, aggressively intervened upon. The prerequisite for breaking various winemaking rules is knowing them inside and out.

La Follette learned plenty of science at the University of California, Davis, from Roger Boulton, Linda Bisson and their colleagues. It's just that when they cautioned about what could happen to yeast under stress, La Follette thought, "Cool! I gotta try that."

Vergari was a year behind La Follette at UC Davis, and part of a generation of students who paid attention to the science part but insisted on questioning it. Many held down internships in other countries, bringing back other viewpoints. Flirting with "heresy" and mastering microbiology went hand in hand. "The reason I went to Davis," he says, "was to understand why things happen. If you don't, you will run into something you don't understand and probably make it worse."

Kongsgaard is no wine Luddite, either, having learned a lot about wine complexity by running experiments on barrel fermentation at UC Davis. But he takes the long view. "Before Pasteur, people were drinking marvelous, beautiful wines made without any knowledge of microbiology, without even electricity. That's a good starting point. We are all grateful for Pasteur, but that doesn't mean you have to get your yeast there."

Oxygen to complexify Roussane     When I heard Bill Easton come out in favor of oxidation, he was responding to comments that seemed to suggest that oxidative character was always and everywhere a bad idea in white wines. What he had in mind in particular was the transformation a little controlled oxidation in the bottle can do to complexify Roussanne, one of the many Rhône wines he makes at Terre Rouge in California's Sierra Foothills. When his Roussanne is first bottled, it's all quince and pears and spices. But after a couple of years in bottle, it takes on a nutty, almond-like character from slow oxidation at a somewhat elevated (3.5) pH, which makes the wine far more interesting for him. It's definitely oxidation, and he could prevent it, he thinks, with enough acidulation, maybe some ascorbic acid, and keeping the temperature down all through processing and aging. But then it would taste like quince and pears and spices forever, and he's already tasted that. The happy marriage of O2 and Roussanne has prompted Easton to try his hand at making a rancio wine, the sor t of thing found in old-fashioned places like Spain and the Jura and Banyuls. Here, the "fault" of oxidation gets turned into the heart of a style, with the wine aged in barrels without topping and without protection from SO2. Easton started this five-barrel experiment in 2003 and recently decided that since they weren't rancio-ing fast enough, he should move the barrels outside to warm up. T.P.

Tim Patterson writes about wine and makes his own in Berkeley, Calif. Years of experience as a journalist, combined with a contrarian streak, make him interested in getting to the bottom of wine stories, casting a critical eye on conventional wisdom in the process. Contact him through edit@winesandvines.com.