A tea infuser is a device in which loose tea leaves are placed for brewing; it is often called a teaball, and sometimes a tea egg. The tea infuser gained popularity in first half the 19th century. By the time of Queen Victoria no respectable household would be without one.
A tea infuser performs the same function as a tea bag. The infuser is generally a small mesh or perforated metal container, ranging in size to brew single or multiple servings at once. Common shapes for infusers include spherical, conical, and cylindrical. One style of infuser is a split sphere with tong-like handles to open its mesh container.
The infuser is placed in a cup or pot of hot or boiling water, allowing the tea to brew without loose tea leaves spilling into the pot or cup. A rod or chain is commonly attached to the container of the infuser to make retrieval from the pot or cup easier. Infusers with large holes may not catch all the leaves, requiring the use of a tea strainer to remove the remaining pieces.
When brewing tea using an infuser, it is advisable to fill it only halfway so that the wet leaves can expand and to increase the surface area of the leaves exposed to the boiling water to allow for quicker brewing.
While not common, a French press may be used as a tea infuser. However, most teas should be infused for a limited time and then removed from the water so that the drink does not become bitter, and while a tea bag or infuser allows this, a French press does not remove the leaves but merely constrains them. This allows extraction to continue after plunging, leading to less control over brewing time and a potentially more bitter brew.