Measuring flour by volume (cups) is inaccurate due to variations in how densely the flour is packed, leading to inconsistent results in baking. Using a kitchen scale provides precise measurements by weight, ensuring consistent and predictable outcomes.
When you use measuring cups to measure flour, you're measuring volume, not weight. The amount of flour that fits into a cup can vary significantly depending on several factors:
Flour Density: Flour can settle and compact over time, especially if it's been sitting in its packaging for a while. Scooping flour directly from the bag can compress it, resulting in more flour in the cup than intended. Conversely, if you've just sifted the flour, it will be lighter and fluffier, meaning less flour by weight in the same cup.
Scooping Technique: How you fill the measuring cup matters. Do you scoop directly from the bag, or do you spoon the flour into the cup? Scooping packs the flour more tightly.
Humidity: Flour absorbs moisture from the air. On humid days, flour will weigh more per cup than on dry days.
Rounding Errors: Recipes often call for fractions of a cup. It's difficult to accurately measure, say, 3/4 of a cup using only measuring cups. Rounding up or down can introduce errors.
A kitchen scale eliminates these issues by measuring the flour's weight directly. Weight is a consistent measurement, regardless of how densely packed the flour is. If a recipe calls for 120 grams of flour, you can accurately measure that amount using a scale, ensuring consistent results every time you bake.
To consistently measure flour by volume (if you don't have a scale), use the 'spoon and level' method: lightly spoon the flour into the measuring cup until it's overflowing, then use a flat utensil (like the back of a knife) to level off the excess. Avoid packing the flour into the cup.