How Can You Tell When Sugar Has Dissolved in Meringue?

The fingertip test is a single step. Stop whipping, take a little of the mixture with the tip of a spoon, and rub it gently between your thumb and index finger. If it feels like sand, sugar crystals are still present. The mixture is ready when it feels completely smooth. Do the test the same way each time and decide based on one test; once you feel any grains, whip for a few more minutes and check again. Wash and dry your hands thoroughly before testing, because moisture on your fingers can dissolve the grains and give a false result.

Looking can help, but it is not enough on its own. Meringue made with dissolved sugar is glossy like silk and reflects light; meringue with undissolved sugar looks matte and dull. When you lift the whisk, a stiff peak should remain upright and should not collapse right away. Still, these signs matter only together; test even glossy-looking meringue with your fingertip. Spreading a thin layer around the side of the bowl and holding it up to the light also makes surface crystals easier to see.

How you add the sugar helps it dissolve. After the egg whites begin to foam, add the sugar gradually; adding it all at once weighs down the foam and lets the sugar sink to the bottom before dissolving. Pour it in a thin stream down the side of the bowl while the mixer is running. Scrape the bottom and sides of the bowl with a spatula now and then, because sugar collected there never reaches the whisk and remains grainy to the end. Scrape only after stopping the whisk; putting a spatula near a spinning whisk is dangerous and can deflate the foam.

The size of the sugar crystals also affects the time. Fine sugar dissolves in a few minutes; coarse sugar crystals may only partly dissolve in the same amount of time. Powdered sugar dissolves quickly, but the starch it contains weighs down the foam, so it is not used on its own. If using coarse sugar, pulse it briefly in a food processor to make it finer. It is also important for the sugar to be dry and free of lumps; sugar that has absorbed moisture clumps together. Sift out any lumps when measuring sugar from the package, because sugar inside a lump will not dissolve.

A grainy meringue is not necessarily a lost cause. Set the bowl over boiling water and stir the mixture constantly while warming it gently; the sugar will dissolve. Then remove the bowl from the heat and whip the mixture again until it cools. This is essentially the Swiss meringue method. If you stop stirring while heating, the egg whites will coagulate. Never put the mixture directly over a flame; heat it only indirectly with steam. Measure the mixture’s temperature with a thermometer, not by touch. If the meringue will not be baked afterward, the mixture must reach at least 71°C / 160°F, or pasteurized egg whites must be used.