Measuring by volume is perfectly acceptable when ingredient ratios are not critical for the recipe's success, such as adding water to soup or a small amount of vinegar to a salad dressing. In these cases, slight variations in quantity won't significantly impact the final result.
While weighing ingredients offers precision and consistency, it's not always necessary or practical. Here's why volume measurements work well in certain situations:
Non-Critical Ratios: Some recipes are forgiving. Adding extra water to a soup, for example, will simply result in a slightly thinner soup, which is easily adjusted. Similarly, a tablespoon or two of vinegar in a salad dressing won't drastically alter the flavor profile.
Convenience: Measuring liquids like water or vinegar by volume is often quicker and easier than weighing them. It requires fewer tools and less cleanup.
Ingredient Properties: For some ingredients, volume and weight are closely correlated. Water, for instance, has a density close to 1 gram per milliliter (or 1 ounce per fluid ounce), making volume a reasonably accurate proxy for weight.
Recipe Design: Many older recipes, especially those passed down through generations, were originally written using volume measurements. Converting them to weight measurements might not improve the outcome significantly and could even introduce errors if not done carefully.
Small Quantities: When dealing with very small quantities, the difference between a precise weight measurement and a volume measurement becomes less significant. A slight variation in a teaspoon of spice, whether measured by weight or volume, is unlikely to ruin a dish.
When using volume measurements, especially for dry ingredients, use the spoon-and-level method. Spoon the ingredient into the measuring cup or spoon and then level off the excess with a straight edge (like the back of a knife) to ensure consistency. Avoid scooping directly from the container, as this can compact the ingredient and lead to inaccurate measurements.