A teabag is a sealed, fine-pore cloth or paper pouch containing whole or chopped tea leaves and/or herbs. When the bag is dipped in hot water (a process known as steeping), the essence of the leaves and herbs infuse into the water. The bag prevents mess and accidental ingestion of the tea leaves.

Tea bags are convenient. They’re disposable, which means you don’t need a metal tea infuser to make a cup of tea. They’re single-serving, which means you don’t need a teapot. They’re biodegradable too! Tea drinkers worldwide should rejoice at this wonder of American ingenuity!

The tea bag was invented in 1904 by a New York tea and coffee merchant named Thomas Sullivan. He decided to package loose tea in small hand-sewn silk bags as an inexpensive and convenient way to distribute tea samples to his customers. To his surprise, his customers brewed the tea in the tea bags rather than removing the contents, thus giving birth to the tea bag.

The Sir Thomas J. Lipton company further improved upon this invention with the introduction of the Flo-Thru Tea Bag in 1952. With four brewing sides, rather than two, boiling water reaches the tea more easily, releasing more of the Lipton “Brisk” tea taste.

Lyons Tetley introduced the round tea bag in 1989 in the UK. At the time, Lyons Tetley was the number two brand in the UK, and like other major brands it was slowly losing its market share to the cheaper generic teas. Then, someone came up with the idea of introducing round tea bags. After Tetley started using them, sales immediately started to grow, increasing inventory turnover by 30%. 18 months later, Lyons Tetley regained brand leadership and has since maintained a 3-4% market share lead in the UK and made significant increases in its worldwide market share.

Since their introduction, the round tea bag has been copied by other companies, most notably by the Republic of Tea, who sells their teas in round tea bags stored in a round cylindrical tin, much like Pringles packs.

But according to a recent study of the kinetics of tea infusion, South African researchers found that it’s the size and not the shape that is important for good tea infusion. The bigger the bag, the more room there is for the flavor to flood out of the tea leaves, regardless of the shape of the bag. Tea leaves swell when infused in water, so water doesn’t flow efficiently through the leaves in the center of a swollen clump of leaves in a small bag. So a voluminous bag seems to be the answer to good tea infusion kinetics. But in the end, it’s the quality of the tea in the bag and not the size or shape of the bag that decides what makes a brisk cup of tea.

The geeky Nature article is here: http://www.nature.com/nsu/011004/011004-10.html

The truly geeky study is here: Jaganyi, D. & Ndlovu, T. Kinetics of tea infusion part 3: the effect of tea bag size and shape on the rate of caffeine extraction from Ceylon orange pekoe tea. Food Chemistry, 75, 63 - 66, (2001).