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Keeping Samples The Right Temperature

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From heating blocks to mantles to baths and circulators, the options for keeping samples heated (or cooled) are many. Within these categories, questions are also plentiful. Users ask our technical assistance team: which bath is big enough or fast enough to meet my needs? Will this device hold my samples at a specified temperature and length of time?

To provide an effective answer, the experts need to know key information. Here are specifics to consider:


  • How much power or capacity is necessary for your application? What total
    volume are you using?

  • What kind of container are samples in?

  • What temperature range is needed? What is the delta or the change in temperature anticipated?

  • How much temperature control do you want for your solution?

  • Are you circulating externally?

  • What fluid are you typically using?

Types of Heating/Cooling Equipment

A laboratory Heating Block warms, cools, or maintains the temperature of samples. Different blocks can be placed into the heated base to adjust to various sizes of sample containers.

Cole-Parmer Benchtop Chilling Heating Black

“Heating/cooling blocks are ideal for warming up or cooling down samples in labs that have limited space. Perhaps there is not enough room for a bath or the lab tech is afraid something will fall into a bath,” said Anthony Murphy, Application Specialist. “Users simply dial in the temperature on the heating block and it remains constant.”

The blocks are best used with smaller samples in plates, vials or tubes. They are typically found in microbiology and life science research.

Hot Plates are a general lab tool and the most common of all of the heating devices. From boiling water to heating other fluids, hot plates are found in academic labs, industrial manufacturing, food & beverage production, and in the pharmaceuticals and paint industries. They are also used in conduction research for silicon chips and for testing temperatures on slides.

“We’re often asked which hot plate is best: aluminum top or ceramic?” said Jennifer Newton, Application Specialist. “Both have advantages. Aluminum offers better heat uniformity but low chemical resistance. Ceramic has higher chemical resistance and holds up better to higher heat.”

Hot plates tend to be a more economical option, yet “their accuracy is limited and they cannot handle high-volume production,” said Newton. “They provide heat only, without any cooling capabilities. Users can add a stirring function to create a multipurpose unit.”

Heating Mantles are used in chemistry labs and small-throughput applications. The heating element inside the mantle is insulated so containers can be placed in direct contact with the mantle. They are much smaller than a bath and provide the real-time temperature of liquids. “The heating mantles will turn themselves on and off to cool or heat a liquid if used with a temperature controller,” said Murphy.

“The mantles are not used for mass production. They work with procedures that involve one vessel with one reaction,” said Newton. “Also, the mantle is specific to the shape of the vessel being used.”

Cole-Parmer Polystat Cooling Heating Circulating Bath

Baths and Circulators, including immersion circulators, constant lab circulator baths, and recirculating chillers, offer higher capacity and volume of production. “Baths heat or cool and maintain the temperature of external material,” said Murphy. “Most baths larger than 5 liters have a recirculating feature using a pump to keep materials at a consistent temperature.”

Baths use a jacketed vessel which contains the reaction within the vessel. “To select an appropriate bath, we ask if the technician will be using an open or closed vessel,” said Newton. “This is significant because it will require a different pump configuration. Some pumps push only, others use a pump to push and another to pull.”

With their capacity and flexible features, baths are used in industrial manufacturing with machinery, and in viscosity testing and specific gravity testing. They thaw samples, cool equipment, and recirculate cooling system water. However, these units do take up space in the lab. “For confined spaces, baths of about seven liters are available and are shaped to be very thin or flat to take up less of a footprint,” said Murphy.

Circulating chillers “have lower tolerances,” explained Newton. “They don’t use water; they simply deliver external circulation. These units work for small-capacity applications, such as laser microscopy.”

Options beyond the typical water baths and circulators include waterless bead baths and sand baths. “Although circulating baths using silicone oil can withstand high temperatures and hold varying sizes of vessels, they get messy and they’re expensive,” said Newton. “The oil slowly degrades. An alternative is the waterless bead bath, which can also handle high temperatures. The beads are recyclable and they use less electricity. Overall, they offer a safer operation over oil baths.”

Sand baths are used for the calibration of temperature probes. They are capable of higher temperatures than silicone oil baths.

The Best Choice?

In terms of price, baths and circulators are the higher end option, with heating blocks also on the more expensive side of the spectrum. However, both offer higher accuracy and are easier to control. The enhanced capabilities and throughput makes the baths and circulators a deeper pocket investment.

“Overall, there is no wrong answer,” said Murphy. “Typically the main concern is if the instrument will have enough power or fit in the space the lab has available. If a customer is not sure, call us and we can help you choose what might be best for the application.”