History of Food – Weights and Measures – Part Four

A baby bottle that measures in all three measu...

A baby bottle that measures in all three measurement systems—metric, imperial (UK), and US customary. (Photo credit: Wikipedia)

British (Imperial) measures

Note that measurements in this section are in imperial units

Traditional British measures distinguish between weight and volume.

  • Weight is measured in ounces and pounds (avoirdupois) as in the U.S.
  • Volume is measured in Imperial gallons, quarts, pints, and fluid ounces. The Imperial gallon was originally defined as 10 pounds (4.5359 kg) of water in 1824, and refined as exactly 4.54609 litres in 1985. Older recipes may well give measurements in cups; insofar as a standard cup was used, it was usually 12 pint [~285 mL] (or sometimes 13 pint [~190 mL]), but if the recipe is one that has been handed down in a family, it is just as likely to refer to someone’s favourite kitchen cup as to that standard.
Table of volume units
Unit Ounces Pints Millilitres Cubic inches US ounces US pints
fluid ounce (fl oz) 1 120 28.4130625 1.7339 0.96076 0.060047
gill 5 14 142.0653125 8.6694 4.8038 0.30024
pint (pt) 20 1 568.26125 34.677 19.215 1.2009
quart (qt) 40 2 1,136.5225 69.355 38.430 2.4019
gallon (gal) 160 8 4,546.09 277.42 153.72 9.6076
Note: The millilitre figures are exact whereas the cubic-inch and US measure figures are to five significant digits.
Note 2: The Imperial Gallon is equal to 10 lbs of water.

American cooks using British recipes, and vice versa, need to be careful with pints and fluid ounces. A US pint is 473 mL, while a UK pint is 568 mL, about 20% larger. A US fluid ounce is 116 of a US pint (29.6 mL); a UK fluid ounce is 120 UK pint (28.4 mL). This makes an Imperial pint equivalent to 19.2 US fluid ounces.

On a larger scale, perhaps for institutional cookery, an Imperial gallon is eight Imperial pints (160 imp fl oz, 4.546 litres) whereas the US gallon is eight US pints (128 US fl oz, 3.785 litres).

The metric system was officially adopted in the UK, for most purposes, in the 20th century and both imperial and metric are taught in schools and used in books. It is now mandatory for the sale of food to also show metric. However, it is not uncommon to purchase goods which are measured and labeled in metric, but the actual measure is rounded to the equivalent imperial measure (i.e., milk labeled as 568 mL / 1 pint). In September 2007, the EU with Directive 2007/45/EC deregulated prescribed metric packaging of most products, leaving only wines and liqueurs subject to prescribed EU-wide pre-packaging legislation; the law relating to labelling of products remaining unchanged.

A 20 US fl oz (591 mL) bottle that displays bo...

A 20 US fl oz (591 mL) bottle that displays both US and Metric units. (Photo credit: Wikipedia)

Special instructions

Volume measures of compressible ingredients have a substantial measurement uncertainty, in the case of flour of about 20%. Some volume-based recipes, therefore, attempt to improve the reproducibility by including additional instructions for measuring the correct amount of an ingredient. For example, a recipe might call for “1 cup brown sugar, firmly packed”, or “2 heaping cups flour”. A few of the more common special measuring methods:

Firmly packed
With a spatula, a spoon, or by hand, the ingredient is pressed as tightly as possible into the measuring device.
Lightly packed
The ingredient is pressed lightly into the measuring device, only tightly enough to ensure no air pockets.
Even / level
A precise measure of an ingredient, discarding all of the ingredient that rises above the rim of the measuring device. Sweeping across the top of the measure with the back of a straight knife or the blade of a spatula is a common leveling method.
Allowing a measure of an ingredient to pile up above the rim of the measuring device naturally, into a soft, rounded shape.
Heaping / heaped
The maximum amount of an ingredient which will stay on the measuring device.
This instruction may be seen in two different ways, with two different meanings: before the ingredient, as “1 cup sifted flour”, indicates the ingredient should be sifted into the measuring device (and normally leveled), while after the ingredient, as “1 cup flour, sifted”, denotes the sifting should occur after measurement.

Such special instructions are unnecessary in weight-based recipes.

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