A Constant Water Bath, also known as a Laboratory Water Bath, is a temperature-controlled device used in laboratories to incubate samples in water at a constant and precise temperature over a prolonged period. It is one of the most fundamental and versatile pieces of laboratory equipment, essential in biological, chemical, medical, and industrial research applications.

The constant water bath works by heating water through an internal heating element and maintaining the temperature using a thermostat or digital temperature controller. The temperature is distributed evenly throughout the bath using natural convection or circulating pumps, depending on the design. These baths can maintain temperatures typically ranging from ambient temperature up to 100°C, though some specialized models can go slightly higher.

Water baths are widely used for warming reagents, melting substrates, incubating cell cultures, enzymatic reactions, sample thawing, and microbiological testing. The constant and gentle heating environment ensures that temperature-sensitive samples are not damaged by sudden or direct heat, unlike ovens or hot plates.

The Constant Water Bath is an essential instrument in any laboratory that requires precise and stable temperature conditions for sample incubation, warming, or reaction control. Its design allows for safe and uniform heat transfer without direct contact with the heating element, making it ideal for sensitive biological and chemical samples. With variations like circulating, shaking, or refrigerated models, the water bath remains a versatile and indispensable tool in modern scientific research and industrial processes.