iStock // Lucy Quintanilla
iStock // Lucy Quintanilla

The Optimal Time to Dunk an Oreo, According to Science

iStock // Lucy Quintanilla
iStock // Lucy Quintanilla

Have you submerged an Oreo into a glass of milk and lingered too long? Did you watch in horror as America's supposedly favorite cookie disintegrated before your very eyes? Fear no more! Here's how to find (and elongate) your optimal dunk time.


Dip your cookie for three seconds, give or take. Carry on with your life, dear reader.


Well, it depends. Do you prefer a crispy cookie masked in a thin veneer of milk? A cookie that has metamorphosed into unrecognizable gloop? Do you believe in a Goldilocks zone, a Platonic middle-ground that’s neither too dry, nor too spongy, but just right? It’s all subjective. But let’s assume you want an Oreo that is pleasantly soggy and has maintained its structural dignity.

There’s math for that. In the late 1990s, Len Fisher, then a professor of physics at the University of Bristol, sparked a media storm when he argued that a decades-old mathematical formula could predict the perfect dunk time for a cookie. It’s all thanks, he claimed, to capillary action.

Water molecules are adhesive: They cling to solid surfaces. (It’s why water in a beaker shows a meniscus—it’s attracted to the sides of the container.) When water enters a small tube, the liquid can adhere to surfaces in ways that seem to defy gravity: This is why water may crawl up your drink’s straw and why a paintbrush seems to slurp up liquid. That’s capillary action in a nutshell.

On a microscale, a cookie is essentially a series of small, starchy tubes. Fisher writes in his book How to Dunk a Doughnut that a dunking liquid (in our case, milk) is “held in place in the porous matrix by the pressure across the meniscus in the smallest of pores.” In other words, capillary action helps the milk spread through the cookie. In the early 20th century, the American scientist E.W. Washburn cooked up a formula to describe this watery journey.

Washburn's Equation
Lucy Quintanilla

Washburn tested and confirmed his formula by observing ink blots spread through paper. (A simplified version of his equation explains how inkjet printers spit out dry, sharp-looking text.) But it took nearly a century for someone such as Fisher to apply the formula to baked goods: After finding reliable numbers for the variables, Fisher rearranged the equation and solved for T (time).

He discovered that the perfect dipping time for a typical British dunking biscuit with a conventional dip was three-and-a-half to five seconds.

But Fisher never tested Oreos. So in 2016, members of Utah State University’s Splash Lab—an academic group studying the behaviors of fluids—put Oreos to the test. (Splash Lab, we should note, has an appetite for quirky experiments: They’ve studied the fluid dynamics of urinal splashback, analyzed the physics of the perfect skipping stone, and even tested the insulating properties of beards.)

Three researchers gathered Oreos, Chips Ahoy, Nutter Butter, and Graham Crackers and dipped the cookies halfway in 2 percent milk for half a second to seven seconds. After dunking, the team weighed the treats and measured how much milk had been absorbed.

The results: Oreos absorbed 50 percent of their potential liquid weight in just one second. After two seconds, they absorbed 80 percent. The number flatlined briefly for a second. After the fourth second, the cookie maxed out: It absorbed all its possible milk. “This data indicates that for the tested cookies, keeping your cookie in the glass any longer than five seconds does not lead to any additional milk entering the cookies,” their study suggested.

A graph of optimal cookie dunk times.
Oreo cookies absorbed milk at the same rate as Nutter Butter, taking in 100 percent of their liquid weight in four seconds.
Splash Lab

Splash Lab then performed a second test, dunking all cookies for six seconds and attaching them horizontally to a clamp. They waited for the cookies to collapse. The Oreo lasted an impressive five minutes! Compare that to measly Graham Crackers, which crumbled after eight seconds.

The takeaway: Three seconds is enough time to saturate most of an Oreo. There’s no benefit to dunking longer than four seconds. (Unless you want to watch the cookie crumble into your milk. As Splash Lab’s Randy Hurd, a mechanical engineering Ph.D. candidate, told us: “Waiting for the crisp cookie structure to break down is not necessarily a waste of time if that’s what you prefer.” We don’t judge.)

However, things get more complicated if you choose a different kind of dairy.


Your choice of milk could change the optimal dunk time by a few split seconds.

In 2011, researchers published a study in the Journal of Food Science that explained why milk doesn’t immediately turn breakfast cereal into mush: Fats and other solids in the dairy hindered “liquid infiltration,” slowing absorption. The same process is true of cookies, says Jennifer Fideler, a graduate student in food science at North Carolina State University.

Milk, for one, is full of sugars. Sugars are hygroscopic, meaning they hold onto moisture and can prevent liquid from seeping into the cookie. Additionally, fat and carbohydrate molecules are big. They can prevent the water in the milk from infiltrating the cookie’s porous matrix.  “Not only is it likely that the fat content of the milk (whole, 2 percent, skim, even heavy whip!) would affect the rate of moisture migration ... but the fat included in the cookie—and even moreso the cream filling—would help resist the influx of fluid,” Fideler wrote in an email.

Fat content doesn’t just slow down absorption time. It’s also known to enhance the flavor. In 1999, Len Fisher tested more than 200 British biscuit and drink combinations and concluded that milk could make a cookie 11 times more flavorful. (This wasn’t peer-reviewed, and it was sponsored by a biscuit company, so take it for what it’s worth.) “Milk is essentially fat droplets suspended in water and those fat droplets stay around in your mouth and they hang on to the flavour in the biscuit so that the aroma can be released up to the back of your nose,” Fisher told the BBC.

So, if you’re the type of person who dreams of extending the optimal Oreo dunk time while enhancing the flavor, toss the skim milk down the drain and pour a cup of high-fat dairy. Whole milk (3.25 percent butterfat) spiked with half-and-half (generally 10 percent butterfat) could extend your dunk time. But if you wanted to indulge and throw a Hail Mary—and have a few spare notches left in your belt—try dunking in heavy cream (36 percent butterfat). Heck, while we’re at it, why not go all the way and dip it in melted butter (80 percent butterfat).

(We’d like to take this moment to say we are not licensed to give nutritional advice and are not liable for culinary crimes against humanity. So maybe don't do this.)


If you wanted to boost the optimal Oreo dunk time even longer, there’s another principle you can hack: Water Activity.

Water activity is a measurement of how likely something gives away moisture. It’s measured on a scale from 0 to 1: Milk, for example, possesses a high water activity of 0.98. It readily gives its water away. A cookie, on the other hand, has a water activity hovering around 0.3. It holds onto its moisture and is more likely to absorb water.

Food manufacturers and processors have to constantly contend with water activity. It’s critical in determining a product’s safety, stability, and shelf life: Controlling water activity is the easiest way to prevent—and predict—the spread of dangerous bacteria [PDF]. (That’s because items with a high water activity are more likely to give water away to nasty microorganisms, causing spoilage.)

But for our selfishly sweet-toothed purposes today, water activity is just another factor affecting the critical cookie dipping time. A liquid with a lower water activity will hold onto its moisture more tightly than standard milk, Fideler explains. So, if you wanted to extend the optimal dunk time further, you should try to dip your Oreo into dairy that not only contains lots of fats and carbs, but also possesses a relatively low water activity. With that in mind, we have the perfect recommendation: Sweetened condensed milk. (We don’t actually recommend this.)

Boasting a high butterfat content (8 percent), obscene loads of carbs (166 grams per cup), and a relatively low water activity (.87), sweetened condensed milk is perfect if you’re the kind of person who relishes long dunk times and believes “calories” are just another government conspiracy designed to scare you from chugging modernity’s decadent ambrosias.

Dunk away!

This story originally ran in 2017.

Just Two Cans of Soda a Day May Double Your Risk of Death From Heart Disease

If you've been stocking your refrigerator full of carbonated corn syrup in anticipation of warmer weather, the American Heart Association has some bad news. The advocacy group on Wednesday released results of research that demonstrate a link between consumption of sugary drinks—including soda, fruit juices, and other sweetened beverages—and an increased risk of dying from heart disease.

Study participants who reported consuming 24 ounces or more of sugary drinks per day had twice the risk of death from coronary artery disease of those who averaged less than 1 ounce daily. There was also an increased risk of death overall, including from other cardiovascular conditions.

The study, led by Emory University professor Jean Welsh, examined data taken from a longitudinal study of 17,930 adults over the age of 45 with no previous history of heart disease, stroke, or diabetes. Researchers followed participants for six years, and examined death records to determine causes. They observed a greater risk of death associated with sugary drinks even when they controlled for other factors, including race, income, education, smoking habits, and physical activity. The study does not show cause and effect, the researchers said, but does illuminate a trend.

The study also noted that while it showed an increased risk of death from heart disease, consumption of sugary foods was not shown to carry similar risk. One possible explanation is that the body metabolizes the sugars differently: Solid foods carry other nutrients, like fat and protein, that slow metabolism, while sugary drinks provide an undiluted influx of carbohydrates that the body must process.

The news will likely prove troublesome for the beverage industry, which has long contended with concerns that sugary drinks contribute to type 2 diabetes and tooth decay. Some cities, including Seattle, have introduced controversial "soda tax" plans that raise the sales tax on the drinks in an effort to discourage consumption.

5 Ways to Define a Sandwich, According to the Law

It’s easy to say what a sandwich is. Grilled cheese? Definitely a sandwich. Bacon, lettuce, and tomato? There’s no question. Things start to get messy when you specify what a sandwich isn’t. Is a hot dog a sandwich? What about a burrito, or an open-faced turkey melt?

The question of sandwich-hood sounds like something a monk might ponder on a mountaintop. But the answer has real-world implications. On several occasions, governments have ruled on the food industry’s right to use the delectable label. Now, Ruth Bader Ginsburg—pop culture icon, scrunchie connoisseur, and Supreme Court Justice—has weighed in on the matter.

When pressed on the hot-button issue as to whether a hot dog is a sandwich while appearing on The Late Show with Stephen Colbert, Ginsburg proved her extreme judiciousness by throwing the question back at Colbert and asking for his definition of sandwich before making a ruling. Her summation? A hot dog fits Colbert's definition of a sandwich, and therefore can be considered one.

While RBG's ruling may not be an official one, it matches Merriam-Webster's bold declaration that a hot dog is a sandwich (even if the Hot Dog Council disagrees). Officially, here’s where the law stands on the great sandwich debate.


Hot dogs are often snagged in the center of the sandwich semantics drama. Despite fitting the description of a food product served on a bread-like product, many sandwich purists insist that hot dogs deserve their own category. California joins Merriam-Webster in declaring that a hot dog is a sandwich nonetheless. The bold word choice appears in the state’s tax law, which mentions “hot dog and hamburger sandwiches” served from “sandwich stands or booths.” Applying the sandwich label to burgers is less controversial, but it’s still worth debating.


When Qdoba threatened to encroach on the territory of a Panera Bread in Shrewsbury, Massachusetts, the owners of the bakery franchise fought back. They claimed the Mexican chain’s arrival would violate their lease agreement with the White City Shopping Center—specifically the clause that prohibits the strip mall from renting to other sandwich restaurants. “We were surprised at the suit because we think it’s common sense that a burrito is not a sandwich,” Jeff Ackerman, owner of the Qdoba franchise group, told The Boston Globe.

The Worcester County Superior Court agreed. When the issue went before the court in 2006, Cambridge chef and food writer Christopher Schlesinger testified against Panera [PDF], saying, “I know of no chef or culinary historian who would call a burrito a sandwich. Indeed, the notion would be absurd to any credible chef or culinary historian.”

Justice Jeffrey A. Locke ruled that Qdoba would be allowed to move into the shopping center citing an entry in Merriam-Webster as the most damning evidence against Panera’s case. “The New Webster Third International Dictionary describes a ‘sandwich’ as ‘two thin pieces of bread, usually buttered, with a thin layer (as of meat, cheese, or savory mixture) spread between them,’” he said. “Under this definition and as dictated by common sense, this court finds that the term ‘sandwich’ is not commonly understood to include burritos, tacos, and quesadillas.”


If you want to know the definition of a certain dish, the officials at the U.S. Department of Agriculture are good people to ask. It’s their job to make sure that the nation’s supply of meat is correctly labeled. When it comes to sandwiches, the agency follows strict criteria. “A sandwich is a meat or poultry filling between two slices of bread, a bun, or a biscuit,” Mark Wheeler, who works in food and safety at the USDA, told NPR. His definition comes from the Food Standards and Labeling Policy Book used by the department (the USDA only covers the “labeling of meat, poultry, and egg products,” while the FDA handles everything else, which is why the USDA's definition excludes things like grilled cheese). Not included under their umbrella of foodstuff served between bread are burritos, wraps, and hot dogs.


The USDA’s definition may not be as simple and elegant as it seems. A sandwich is one thing, but a “sandwich-like product” is different territory. The same labeling policy book Mark Wheeler referred to when describing a sandwich lumps burritos into this vague category. Fajitas “may also be” a sandwich-like product, as long as the strips of meat in question come bundled in a tortilla. Another section of the book lists hot dogs and hamburgers as examples of sandwich-type products when laying out inspection policies for pre-packaged dinners. So is there an example of a meat-wrapped-in-carb dish that doesn’t belong to the sandwich family? Apparently strombolis are where the USDA draws the line. The Food Standards and Labeling Policy Book clearly states the product “is not considered a traditional sandwich” [PDF].


When it comes to sandwiches, New York doesn’t discriminate. In a bulletin outlining the state’s tax policy, a description of what constitutes a sandwich warrants its own subhead. The article reads:

“Sandwiches include cold and hot sandwiches of every kind that are prepared and ready to be eaten, whether made on bread, on bagels, on rolls, in pitas, in wraps, or otherwise, and regardless of the filling or number of layers. A sandwich can be as simple as a buttered bagel or roll, or as elaborate as a six-foot, toasted submarine sandwich.”

It then moves on to examples of taxable sandwiches. The list includes items widely-believed to bear the label, like Reubens, paninis, club sandwiches, and peanut butter and jelly sandwiches. Other entries, like burritos, gyros, open-faced sandwiches, and hot dogs, may cause confusion among diners.