You’re at a dinner party at Sam’s house. Sam mostly drinks wine made by producers and from grapes you’ve never heard of. He pours you a glass of his favorite new pét-nat. It’s tasty! It reminds you of watermelon sour candy with a spritzy finish.

After it sits for a minute, though, you find yourself liking it less. As it warms, it starts to taste… sour? Like bad kombucha? With notes of nail polish remover? Sam rolls his eyes.

“I guess you just don’t like natural wine,” he scoffs. “It’s fine, not everyone’s palate is there yet.”

Huh?

First of all, you should probably find wine-loving friends who are less obnoxious than Sam. Secondly, he’s about 30 percent right and 100 percent rude.

What you were reacting to in that tangy, kombucha-y wine was probably volatile acidity (VA). It’s a combination of compounds — primarily ethyl acetate and acetic acid — that are present in small amounts in pretty much every wine. When a wine has a lot of VA, it can have acetone-y, vinegary, kombucha-esque notes. And, like many things in wine, VA can be divisive.

According to Victoria Burt, product development manager for wine qualifications at the Wine & Spirit Education Trust (WSET) and Master of Wine, VA “mainly refers to acetic acid, although some other compounds can contribute.”

Burt explains, “Acetic acid in turn reacts with the alcohol in the wine and becomes ethyl acetate (nail varnish remover smell), which is also perceived as a fault when in excess.”

It’s important to note that wines with VA don’t necessarily taste unpleasant to most drinkers, nor is the mere presence of VA a fault.

“Personally, I love a hint of juicy-vinegar, fermented fruit aromatics. It can really hit the spot in a light-bodied red served slightly chilled on a sunny day in the park,” Dan Belmont, London-based wine and cheese educator and WSET Level 3, says.

“The likelihood of the presence of VA in wine increases as you lean harder into minimal intervention winemaking, so no surprise that ‘trendy’ wines all seem to express VA,” he adds.

VA is not necessarily a hallmark of natural winemaking, though, Jared Brandt, winemaker and co-owner of the Berkeley, Calif.-based winery Donkey & Goat, says.

“For me, it is like many other ‘flaws’ in wine; a little is awesome in balance,” Brandt says, adding, “I think they are often way out of balance. It’s O.K. for VA to be a note but it’s not enjoyable for it to be the whole thing.”

Furthermore, Brandt says, “I think it’s been a disservice to natural wine to have so many examples be flawed. It’s funny, a woman — who has become a good friend — once told me our wines are ‘too clean’ to be natural.”

Burt says VA is caused by acetic acid bacteria, inadequate levels of sulfur dioxide, and excessive exposure to oxygen. Sulfur dioxide  — sometimes called SO2 — is one of a few hundred approved wine additives and is used as a preservative. In Brandt’s experience, though, it’s not necessarily a lack of sulfur that’s the culprit when it comes to VA.

“We do everything we can to keep our levels [of VA] low,” he says. “We try to be as clean as possible, running ‘pigs’ [strong cleaning sponges] through our hoses daily to make sure the interior surface is clean. I love my steamer and use it often. We top, we taste, and we sell off wines with VA for bulk. We have found that being fastidious in our work keeps our numbers down without SO2.”

At the end of the day, says Brandt, “VA is complicated.”

Belmont agrees. “It’s all about balance,” he says. “There’s a time and a place (and a wine) for all things.”