The main piece of a French press is a glass beaker. Because the beaker is exposed to high temperatures in a short time, they are subject to thermal shock, This is why beakers for French press coffee makers are made of borosilicate glass, or more recently, of stainless steel.
A beaker is a simple container for stirring, mixing and heating liquids commonly used in many laboratories. Beakers are generally cylindrical in shape, with a flat bottom. Most also have a small spout (or “beak”) to aid pouring as shown in the picture. Beakers are available in a wide range of sizes, from one millilitre up to several litres.