Vol. I · What Cooking Does Plate 5 of 10weighing, scale, cup, volume, flour, hydration, baker's percentageTF

Weighing, Not Scooping.

A cup measures space, not flour. Sifted, spooned or scooped, the same cup holds different amounts — and the dough knows the difference.

Flour is a powder full of air. Sifted into a cup it lies loose; spooned in and levelled it settles; scooped straight from the bag and packed against the side it holds much more. The cup is full every time, but the flour in it is not the same. For a sauce this hardly matters. For bread, where the ratio of water to flour decides whether the dough is stiff or slack (Vol. XXIV), it matters a great deal.

Professional bakers weigh everything, including water and eggs, and so do recipes written in most of the world. The workshop makes a simple bread dough from "4 cups of flour and 1½ cups of water" filled three ways, and shows what the baker actually got.

Below: the grams of flour in 4 cups filled each way, and the hydration (water as a percentage of flour) of the dough each makes with the same 355 g of water.

What you will learn

Explain why volume measures of powders are unreliable.
Convert between cups and grams for common ingredients.
Compute a dough's hydration from weights.
Use a kitchen scale and the tare button.

Workshop

Flour per cup by method (course values within the range published by baking references: sifted about 113 g, spooned and levelled about 125 g, scooped and packed about 142 g). The same 355 g of water makes doughs of very different hydration.

Ratios need weights

Four cups of flour weigh 452 g sifted and 568 g scooped and packed, a difference of 116 g — 23 % of the spooned weight. With the same 355 g of water the dough is 79 % hydration in one case and 62 % in the other: the first a slack, sticky dough for an open-crumbed loaf, the second a stiff dough for a tight sandwich loaf. Both cooks followed the same recipe.

A scale removes the question. Put the bowl on it, press tare to zero it, add flour to the weight; tare again, add water. Liquids can be weighed too (a millilitre of water weighs a gram), and so can eggs — a large egg is about 50 g without its shell. This course gives quantities in grams first, with cups beside them only where a home cook needs them; Vol. XXIII.4 has the conversions.

At the stove

Fill a cup three ways — sifted, spooned and levelled, scooped and packed — and weigh each. Your numbers will differ a little from the workshop's, because flours and cups differ, which is the point.

If you must use cups, spoon the flour in and level it with a knife, and use the gram weight the recipe was written with whenever it gives one.

The American cup is 236.6 mL (legal cup, for labels, 240 mL); the British and Australian metric cup is 250 mL; the Japanese cup 200 mL; the Chinese 市制 measures 斤 and 两 are weights — half a kilogram and 50 g.

Terms

Tare: Setting a scale to zero with the container on it, so it weighs only what you add.
Hydration: The weight of water in a dough as a percentage of the weight of flour.
Volume measure: A cup or spoon: it measures space, so it depends on how the ingredient is packed.
Bulk density: Mass per volume of a powder including the air between grains; it changes with packing.

A cup measures space, not flour. Weigh dry ingredients whenever the ratio matters.

Sources

A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.
USDA FoodData Central, SR Legacy (April 2018), public domain.