When tea is brewed in the traditional manner in a teapot, the tea leaves are not contained in teabags, but rather are freely suspended in the water. As the leaves themselves may be distasteful, it is usual to filter them out with a tea strainer. Strainers usually fit into the top of the cup to catch the leaves as the tea is poured.
Some deeper tea strainers can also be used to brew single cups of tea, much as teabags or brewing baskets are used - the strainer full of leaves is set in a cup to brew the tea, and then removed, along with the spent tea leaves, when the tea is ready to drink. By using a tea strainer in this way, the same leaves can be used to brew multiple cups.
Tea strainer use declined in the 20th century with mass production of the tea bag, but is still preferred among connoisseurs who claim that keeping the leaves packed in a bag, rather than freely circulating, inhibits diffusion. Many assert that inferior ingredients, namely dust quality tea, are often used in tea bags.
Tea strainers are usually either sterling silver, stainless steel, or china. Strainers often come in a set, with the strainer part and a small saucer for it to sit in between cups. Tea strainers in themselves have often been turned into artistic masterpieces of the silver- and goldsmith's craft, as well as rarer specimens of fine porcelain.
Brewing baskets (or infusing baskets) resemble tea strainers, but are more typically put in the top of a teapot to contain the tea leaves during brewing. There is no definitive boundary between a brewing basket and a tea strainer, and the same tool might be used for both purposes.
Tea strainers are also used by patients trying to pass a kidney stone. The patient urinates through the strainer, thereby ensuring that, if a stone is passed, it will be caught for evaluation and diagnosis.