Did you know there is an international standard for a cup of tea? Following World Standards Day (14 October), I investigate what that means.

A pervasive form of clickbait I’ve noticed, particularly in the British tabloid media, is that of the Great British Tea Debate. The playbook goes a little like this: a piece of scientific or historic research suggests there is a codified way to make a cup of tea. An explosion of indignant and defensive comments ensues.

Whether it’s a debate on milk-first or milk-after, a discussion on the difference between high, low and afternoon tea, or a tussle about which teas make up a traditional English breakfast blend, the result is a superhighway’s worth of traffic to the site. A cynical tea lover might see these debates as a profit-making venture for the media.

The issue, of course, is that the ‘correct’ way to make a cup of tea is entirely subjective and done to your own taste. Sure, if you want to steep leaves for 10 minutes and put milk after and only drink from stainless steel mugs then that’s your preference and no one should argue with that being ‘correct’ in your view. But did you know there is a ‘standard’ cup of tea?

Since 1980, the International Organization for Standardization (commonly known as ISO for ironically non-standard reasons) has had a standard for making a cup of tea. ‘ISO 3103: Tea—Preparation of liquor for use in sensory tests‘ is derived from the British Standards Institution guidelines and is revised every five years.

Among the recommendations are:

• Use of a white vessel made of porcelain or glazed earthenware (e.g. ceramic)
• A tea-to-water ratio of 2g per 100ml
• Freshly boiled water
• A six-minute steeping time
• If milk is used, it’s at a milk-to-tea ratio of 2.5ml per 150ml, with tea poured on the milk, that is, milk-first

If you have 38 Swiss francs, you can purchase a copy of the full standard documentation or its sister standard, ‘ISO 1839:1980 Tea—Sampling‘, which includes sampling from container of any size.

Why create a standard? It’s largely for those in the industry to compare tea—from plantation to plantation, harvest to harvest—on a level playing field. If the tea is always prepared in a standard way, then parameters like differences in tea-to-water ratio, water temperature and brewing time won’t change the test.

Of course, brands often have standards internal to their organisation and plantations and regions may have their own, but it’s nice to know someone has actually thought about how to compare tea on an international level.

This article originally appeared in AUSTCS enews 22 October 2018.