Units of Measurement

From Eating Asturias, the Encyclopedia of Asturian Gastronomy
Measuring Cups with Leftover Flour
Measuring Cups with Leftover Flour

The units of measure I use in recipes on this website might be unfamiliar to you. This is because you (like me) grew up with an utterly bizarre mish-mash of weights designed to measure sheep's wool in the middle ages, dry volume measurements based on Edward III's definition of a bushel, and the (estimated) sizes of the spoons found in the apron of one specific cooking school instructor in 1896.

Outside of a very small number of recipes that can be reduced to simple volume ratios, such as cooking rice in water, these measurements are more of a hindrance than a help to the average home cook. (Those simple ratios are more accurately described as "eyeballing it because the actual ratio doesn't matter much". For all other recipes, it helps to understand a little about what is going on when you are cooking.

Some Science

Most cooking operations that require a recipe are a complicated chemical or thermodynamic reaction. The reproducibility of those reactions depends on the ratio of the various molecules or atoms available in the reaction. The equipment needed to count molecules is not available in kitchens (not most kitchens anyway), so to some extent, we are all guessing.

However, The number of molecules in a physical object is directly proportional to the mass of that object, so we can get a really good approximation simply by weighing the objects. Unfortunately, volume is a terrible approximation of weight unless you know the actual molecule count in a given weight of one specific instance of a foodstuff, and have accurately calibrated your volume measuring apparatus to compensate for the variation from the last batch. Theoretically the density relation is simple, but only under laboratory conditions. In an actual kitchen, where the ambient humidity can change the volume/weight ratio several times in a single day (say for flour used to make bread dough), volume simply doesn't work.

Measurement Woes

Ingredient conversion failure
Software is not good at conversion

Dry ingredients simply cannot be measured accurately by volume. Flour, baking soda, even salt, can vary by 20% or more in density from manufacturer to manufacturer, and bag to bag. Grain size, milling machinery differences, ambient humidity, and a few other variables intrude to make batch to batch volume comparison impossible.

Ever wondered what firmly packed, lightly packed, leveled, rounded, heaped, or sifted meant in a recipe? It meant that measuring was hopelessly inexact and basically impossible and you should just wing it. Volume measures are inherently inaccurate. Those modifiers can change the amount of an ingredient in a recipe by a third or more. That's a really error prone and dumb way to cook.

Oh, and did you know that not all tablespoon measuring spoons in common use are equivalent to three teaspoons, even from the same set of spoons? The same goes for liquid measuring cups, by the way. They're not nearly as accurate as you think they are either.

The Solution

I am convinced that our unthinking adherence to volume-based measurements is responsible for quite a bit of why so many Americans think cooking is difficult. Instead, cooking should be done by mass. That is, by weight. Weight-based recipes need no ridiculous modifiers to try (and fail) to account for different densities of an ingredient from batch to batch, manufacturer to manufacturer, or location to location. It does not matter one bit which flour you use in North Carolina or which one I use in Asturias. 100 grams of flour is 100 grams of flour. There is precision, and more importantly, confidence.

And no, those automatic US to Metric converters that some recipe blogs have are not useful. You cannot simply convert volume to mass because each manufacturer or batch of ingredient will have a slightly different density.