Teatime!

You may be surprised to learn that there is an International standard for preparing the drink tea, ISO 3103, titled "Tea - Preparation of liquor for use in sensory tests".

It was originally laid down in the Bristish Standard BS6008 in 1980. ISO 3103 was produced by International Organization for Standardization (ISO) Technical Committee 34 (Food products), Sub-committee 8 (Tea).

ISO 3103:1980 / BS 6008:1980

Apart from explaining the procedure for making tea (both with and without milk), the standard also specifies recommended pots and bowls to use.

The standard is not meant to define the only proper method for brewing tea, but rather how to brew tea 'for use in sensory tests', or taste-tests. There is also the related standard ISO 1839 "Tea - Sampling" (equivalent to BS 5987 "Methods for sampling tea"), which details the sampling process referenced by ISO 3103:1980.

The standards referred to above are protected by copyright, but the prcedure calls for adding boiling water to the tea leaves, and letting the tea infuse for a full 6 minutes. Some key details are given below:

Equipment

The pot for brewing the tea must be white porcelain or glazed earthenware and have a loose fitting lid
If a large pot is used, it must hold a maximum of 310 ml (±8 ml) and must weigh 200g (±10g)
If a small pot is used, it must hold a maximum of 150 ml (±4 ml) and must weigh 118g (±10g)
The tea is poured into a white porcelain or glazed earthenware bowl for tasting
If a large bowl is used, it must have a capacity of 380ml and weigh 200g (±20g)
If a small bowl is used, it must have a capacity of 200ml and weigh 105g (±20g)

Method

2 grams of tea (measured to ±2% accuracy) per 100ml boiling water is placed into the pot
Freshly boiled water is poured into the pot to within 4-6mm of the brim
The water must not be hard
Brewing time is six minutes
The brewed tea is poured into the white porcelain or glazed earthenware bowl for drinking

Preparation with milk

Milk should be free from any off-flavour (for example raw milk or unboiled pasteurized milk)
5ml of milk (for the large bowl), or 2.5ml (for the small bowl), is used
The tea should be poured into the bowl after the milk, in order to avoid scalding the milk (unless this procedure is contrary to the normal practice in the organisation concerned)
Milk poured after the tea is best added when the tea is between 65-80°C

Competing standards

In 2003, the Royal Society of Chemistry published a news release entitled "How to make a Perfect Cup of Tea". The main difference is the length of time the tea is brewed for (3-4 minutes), and the allowing of a ceramic mug. It also gives details for warming the pot before brewing.

Previous 'standard brews'

The publication of the standards BS 6008 & ISO 3103 in 1980 came after the phrase "NATO Standard" cup of coffee or tea (specifically comprising milk and two sugars) - military slang going back to the late 1950s and parodying NATO's relentless bureaucratic drive to standardise parts across European and US militaries.

An alternative phrase (before ISO 3103 was published) was the "ISO Standard" cup of tea (with milk and one teaspoon of sugar), where the milk is poured into the cup before the tea. Variations are ISO 0, with no sugar; ISO 2, with two spoons of sugar; and so on.

Like many ISO standards, this one could cause problems in North America, where the civilised practice of adding dairy products is commonly shunned in favour of a wedge of lemon. An analagous "ANSI Standard" cup of tea could therefore be proposed, but this would result in a cross-standard situation depressinigly similar to several that arise in much more serious technical contexts (ie milk and lemon do not mix very well).