Recently I had an entire day derailed when I overheard someone’s order at Dunkin’: a medium coffee with five sugars and seven creams. Five. Sugars. Seven. Creams. Doing just a little bit of math: a medium coffee cup is 14 ounces, and for sake of argument, we’re going by this Reddit answer, which says that “one cream” and “one sugar” means one teaspoon each, and six teaspoons equals one ounce. So this person’s drink was approximately 12 ounces of coffee and two ounces of cream and sugar mix. It makes me shudder just to think of it.
But now that we’re done with the math portion of the day, let’s talk about the science: At what point does sugar stop dissolving into a drink? Is there a threshold beyond which you just end up with soggy sugar residue at the bottom of your finished coffee cup? What’s the exact amount of sugar you can add to your coffee before you’re just wasting everyone’s time (including your own)?
First, let me reach into the depths of my brain to define some terms from my high school chemistry class with help from this ThoughtCo. article by Dr. Anne Marie Helmenstine. When you add sugar (a solute) into coffee (a solvent), you create a solution, simply defined as a mixture of two or more substances. That mixture becomes a saturated solution when the maximum possible solute has been diluted into the solvent. In coffee terms, that means that once you hit that maximum saturation, the sugar just stops dissolving and you’re left with floating crystals that do little to actually sweeten the coffee, unless you get a gritty, too-saccharine mouthful of the sugar crystals themselves.
Temperature matters. If you’re drinking hot coffee, you’ll be able to dissolve much more sugar into your drink—solubility increases with heat. There’s also chemical composition to consider. A liquid sweetener already has sugar dissolved in as a saturated solution and will more easily mix with coffee of any heat. Because that compound is at max sugarization (a real scientific term, I’m sure), the more of the syrup or other form of liquid sweetener you add, the more sweetness you will actually be getting without worrying about a sugary silt at the bottom of your drink.
If you want to stick with solid sugar, you might need to work on some trial and error at home. Knowing that most coffee shops consider “one sugar” one teaspoon, make yourself a cup of coffee (hot or iced depending on your preference) and get out the measuring spoons. Stir in one teaspoon of sugar at a time until you notice it’s no longer dissolving. Whatever number spoon that is, that’s the limit of that particular compound’s sweetening ability.
Because heat is so important to solubility, if you’re an iced coffee drinker with a sweet tooth, you may want to stop using the solid stuff entirely. A typical “pump” of a syrup sweetener at somewhere like Starbucks is about 1/2 tablespoon of the stuff. Again, you can test this out at home to find your preferred flavor and pumps per cup or, if you don’t want to invest in at-home coffee syrups, try testing it out in the wild at various coffee shops. If you also take your coffee with cream (like our seven-cream friend from earlier), consider what dairy options might be the sweetest for an extra kick.
Once you’ve perfected your ratio, go out into the world and order that coffee with confidence! You’re getting the exact right amount of sugar without wasting a single grain, and that’s something to be proud of.