Water Bath- Definition, Principle, Parts, Types, Procedure, Uses

Laboratory hot water bath is one of the important laboratory instruments. Its application is important for samples to incubate underwater for a long time at a constant temperature.

It has a large heating vessel with a heating element that is filled with water. Container sizes can range from 12-32 liters and 50-100 liters.

Has application in clinical and microbiology laboratories, such as food technology industries, environmental research laboratories for warming reagents, thawing samples, examination in bacteriological experiments, etc.

They are an ideal choice when high-temperature balanced heating requires no more than 100 degrees Celsius to treat the samples.

Water Bath Principle

The water bath works in the presence of a Cu50 temperature sensor which transfers the water temperature in the device up to a resistance value which is amplified and compared with an integrated amplifier, which then puts into the output control signals and maintains the optimum heating power of electric heating tube and thus keeps the bath at a constant temperature.

Since the water, the bath is a heating device, and in this device, water is used as a medium to transfer heat into the component of the sample solution, and since water reaches the boiling temperature of 100 degrees Celsius, thus, temperature-sensitive glassware or sample should not be treated using this method.

Water Bath
Figure: Water Bath. Image Source: ZZKD.

The temperature range in the water bath: 

  • Ranges between 30-100 degrees Celsius.
  • To keep the temperature constant, the water bath uses the circulated heat to generate motion while heating inside the sample. But if the sample requires a temperature above 100 degrees Celsius, then an oil, sand, and silicone bath is preferred.
  • Oil bath: instead of water, oil is used, such as soybean oil, cottonseed oil, etc. and it can maintain temperature up to 300 degrees Celsius. It can provide more uniform heat compared to other types.
  • Sand bath: sand is used as a heating substance, in which yellow sand is used where heat transfer of sand is weaker than water and oil. The heating element is made up of aluminum. Very precise and works at low temperatures as well.

Types of water baths

  1. Circulating water bath:
  • Aka stirrers
  • It can be used when temperature uniformity and consistency are required
  • For eg, enzymatic or serological experiments
  • Water circulates thoroughly to maintain a more uniform temperature.
  • Rapid heating or cooling with a wide range of temperatures.
  • It can be equipped with touchscreen operation and control keys such as temperature accuracy control, temperature uniformity range, heating rate, etc.
  1. Non-circulating water bath:
  • Works on the principle of convection rather than of water
  • Less accurate in terms of temperature control
  1. Shaking water bath:
  • Additional shaking control makes it an idea
  • Continuous shaking promotes cell growth when mixed with air.
  • Constant temperature control with controlled shaking makes it demanding.
  • High precision
  • Convenient in temperature adjustment
  • Accuracy and intuitive indication
  • Reliable performance
  • Equipped with an additional lightning device for observation
  1. Digital water bath:
  • Digitally maintain temperature
  • Ranges from 32-80 degrees Celsius
  • Simplest analog water bath
  • Cost-effective
  • Simple to operate
  • Disadvantages include less accuracy
  • More accurate than analog water bath

Parts/components of Water Bath

  1. Container or tank bath
  2. Heater
  3. Thermometer
  4. Thermostat or regulator

Procedure for running Water Bath

  1. Fill the water bath tank with distilled or deionized water. Ensure that the water level should above the level of the heating rod and that it should be fully immersed in water.
  2. Cover the lid and switch ON the machine. In the digital water bath, there is a display screen that will show the set value (SV) and present value (PV), thus, setting the value of your need.
  3. If the water bath is of the analog type, then rotate the knob of the thermostat to the desired temperate and set the value.
  4. Water bath now will take some time to reach the value set by you.
  5. When the temperature reaches the set value, keep the sample immersed in a water bath.
  6. Cover the lid and set the required timer.
  7. After completion, carefully take the samples out and switch OFF the machine.

Uses of Water Bath

  • Used for warming of chemical reagents
  • Used for melting of substance
  • For incubation of cell cultures
  • Used to improve the solubility of a poorly soluble substance
  • Used as a heat source for some substances such as flammable chemicals.

Advantages of Water Bath

  • Easy operation
  • Cost-effective
  • Low maintenance
  • No direct heat transfer to sample.
  • Smooth way of heating the sample
  • Provide a large surface area for more samples
  • A shorter time is required.

Disadvantages of Water Bath

  • Risk of handling
  • Corrsosion of material
  • No precision in temperature control
  • Heat sensitive sample can not be used
  • Electricity dependent
  • Temperature fluctuation
  • Too many sources of contamination of samples
  • Samples can spill due to poor sample holding capacity


  • The machine should be kept away from all the power sources.
  • A stable, solid, and hard surface should be selected to keep the machine.
  • Never fill the water bath with tap water because it will contain ions and minerals, which will make the corrosion of the bath more likely.
  • The heating rod or heating element should be fully immersed with the water, or it will overheat and cause damage.
  • The water bath should be emptied at the end of the day, followed by cleaning and drying to avoid rusting, which can contaminate the samples.
  • To get rid of rust, anti-rust chemicals can be used. Moreover, Collins can be used to remove dust and dirt particles.
  • To check the working of the water bath, a manual thermometer should be used immersed to check the temperature of the water bath and compare it with the present value of the water bath.


  1. https://www.tec2med.com/water-bath-working-handling-maintenance/
  2. https://antiteck.com/laboratory-water-bath-2/
  3. https://microbiologynote.com/laboratory-hot-water-bath-working-principle/
  4. https://www.slideshare.net/goldenalzaidy/pdf-water-bath-laboratory-applications

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