An Old-School Technique Finds Modern Winemaking Fans

It’s the year 2025 and winemakers have a full suite of technology at their fingertips that can help analyze, assist and predict every step of the winemaking process. Optical machines can sort grapes, machines can regulate tank temperatures and acidity. Computers can measure other details that dictate a wine’s doneness in seconds.

Certainly, technology has its upsides. But in contrast, some winemakers are leaning into the analog. They’re unpacking their beakers and test tubes and measuring malic, lactic and tartaric levels through paper chromatography, a process similar to how film is developed. 

“It’s an extremely old-school process,” says Ryan Alfaro, the winemaker at Alfaro Family Farms and Farm Cottage Wines in the Santa Cruz Mountains. “I learned this from my dad.” 

Justin Phillips, the assistant winemaker of Rosewood Winery and Meadery in Niagara, Canada, learned it in winemaking school, but still employs it in the winery. 

It isn’t a commitment to tradition or a love of ephemera drawing both him and Alfaro to the process. Paper chromatography, it turns out, is a speedy, reliable and affordable way to test acid levels in a wine undergoing second fermentation. 

And if it ain’t broken, why fix it?

What Is Paper Chromatography?

Essentially, paper chromatography is “a really quick, efficient analytic test for winemaking,” says Phillips. “All it really requires is a special type of filter paper, a solvent and a jar. It gives us a sense of, ‘Okay, we’re on the way.’” 

The process starts by winemakers gathering samples from every barrel. The still-fermenting product (either wine, must or juice) is dotted onto a piece of chromatography paper. 

“On the paper, you put different acid standards—lactic, malic and tartaric acid standards,” explains Phillips. The paper is placed in a jar of solvent (similar to the solvent used for film development) and then hung up to dry. 

There are many acids present throughout a wine’s lifespan. Malic acid is one of the most common organic acids found in grapes, but the hyper-tart substance is best known for its role in malolactic fermentation. The process follows malic acid as it’s converted into soft, creamier lactic acid (the same acid found in milk, and that gives many California Chardonnays their controversial butteriness). 

There’s also tartaric acid, which helps control the acidity of a finished wine (and the finished wine’s pH level). 

As the page dries, the solvent will evaporate, leaving streaks of yellow, red and green across the blue paper. The level of contrast and the color of each sample will indicate how much malic, lactic and tartaric acid are left in the wine and the farther the colors travel on the paper, the further through its transformation the wine is. 

Squiggles of malic acid on the page? It means your Chardonnay is still lean and mean. As those evaporate, the white wine gains all rich unctuousness.

Why Use Paper Chromatography?

For Alfaro, using paper chromatography is a no-brainer: it’s quick, easy and dependable. If you’re curious about how a wine is progressing, he says, simply pop open the barrel, extract some of the fermenting liquid and drip. You’ll have the answer in the morning.  

“You can tell which barrels are actually going through secondary fermentation—whether it’s started or how long it’s going,” Alfaro says. 

The cons? “I wouldn’t say paper chromatography is a lost art, but people aren’t as interested in doing it anymore because it’s very time consuming,” he says. 

Alfaro and his father make a wide range of single-vineyard Chardonnay, Pinot Noir and Grüner Veltliner from across the Santa Cruz Mountains. That means their winery is full of barrels of this and that—a Bates Ranch Cabernet Sauvignon here, leathered but juicy Pinot Noirs from Corralitos there. 

To test each barrel, Alfaro has to climb over each barrel one by one, dip in his pipette and go through the process. “You feel a bit like a mad scientist,” says Alfaro.