There are a number of standard laboratory procedures and processes that need to be conducted at specific and stable temperatures. As this temperature may be either above or below room temperature, devices capable of both heating and cooling are required in most labs. In many cases it is essential to achieve a precise temperature, sometimes to within a tenth of a degree Celsius, and usually this temperature must be maintained for a period of time without significant fluctuation.
Over the years, devices used to achieve appropriate temperatures in the lab have become increasingly sophisticated. The water bath has evolved from a simple heated vessel to a precision instrument that is carefully calibrated and engineered to offer accuracy and reliability. Many types of laboratory water baths now exist, including circulating water baths, shaking water baths, and digital water baths. Recently, waterless lab baths using small beads instead of water have become popular. Waterless baths avoid the contamination that can be a problem with traditional water baths, use less energy, and have a reduced risk of causing burns or injury.
While water and waterless baths are used to elevate temperatures, lowering temperatures can be achieved using lab chillers. Chillers are refrigerators that cool down samples or processes to preset temperatures by removing heat from one element and transferring it to another, typically air or water. Chillers operating down to temperatures near -40ºC are relatively inexpensive and use a single compressor. Chillers offering a temperature range of -40ºC to -95ºC are available, but rely on two compressors and are therefore significantly more costly. Some chillers also provide modest heating, to about 40ºC.
The following article presents some of the key milestones in the development of lab water baths and chillers:
In 1748, artificial refrigeration was demonstrated for the first time by William Cullen of Glasgow University, UK.
In 1851, the first ice-making machine was invented by John Gorrie. Ice baths quickly became a popular way of cooling reactions and other lab processes, and this low-tech technique is still frequently used today.
In 1876, a continuous process of liquefying large volumes of gas was invented by the German engineer Carl von Linde. This invention eventually made chilling and refrigeration possible on a domestic and industrial scale and laid the groundwork for the development of the modern refrigeration industry.
In 1921, the first centrifugal water chiller was patented by an inventor named Willis Carrier. Before this time, chillers used a reciprocating compressor to move the refrigerant through the system. The main part of a centrifugal chiller is the centrifugal compressor. The design of the first centrifugal compressor was similar to the centrifugal blades in a water pump.
During this time, lab processes that required elevated temperatures tended to be heated directly over a flame, or conducted in a water bath which was itself heated directly. However, the number of naked flames used in labs at this time represented a major fire hazard, particularly as many of the solvents being heated were highly flammable. This problem was resolved in the 1930s by husband and wife team Glen and Ruth Morey, who invented the heating mantle, a reliable and non-flammable heating device with electric resistance wires woven into a fiberglass cloth sheath. The first heating mantle was sold in 1939, and the couple formed the Glas-Col Apparatus Company to manufacture their new product.
In 1950, the first industrial chiller was designed for use in the plastics industry.
1950s and 1960s
During the 1950s and 1960s, water baths became more sophisticated, offering improved control and a greater number of features. For example, during this time, New Brunswick Scientific developed the G76 water bath shaker, which used a triple eccentric drive to achieve optimal shaking while maintaining the temperature within a controlled range. The company claims this iconic water bath shaker is still being used in many labs worldwide today.
During these decades, New Brunswick Scientific also developed the first refrigerated incubator shaker.
In 1984, New Brunswick Scientific updated their classic G76 water bath shaker by introducing the G76/D model. This instrument used much of the same technology as the original model, but incorporated microprocessor technology for much greater control over temperature and speed. The G76/D was able to control temperature to within 0.1°C and speed to within 1 rpm.
In 1994, Yamato completed improvements in its lowtemperature water bath series and low-temperature/constanttemperature incubator series in response to fluorine regulation.
In 1999, Julabo released a series of water baths and shaking water baths that offered splash-water protection to protect the user and samples during use. Also in this year, Julabo launched the Economy series of circulators featuring LED displays for increased energy efficiency and improved ease of use.
Between 2000 and 2006, Julabo introduced a range of innovations to the field of lab circulators, offering alternative ways to heat and chill laboratory processes. For example, the new High Temperature Circulator Forte HT was introduced in 2001, followed by the new High Dynamic Temperature Control Systems Presto LH. In 2003, the company developed three new new circulator/bath product lines, and in 2004 they introduced new calibration circulators. The EH circulator series was launched in 2005, followed by the FL Chiller and CF Cryo-Compact series of circulators in 2006. These innovations helped make circulators a viable alternative to more traditional methods for controlling the temperature of water baths and chillers.
In 2007, Grant Instruments began selling two new unstirred water baths intended for everyday use in general laboratories; the SUB Aqua range, which was a digital instrument; and the analog JB Aqua range. These instruments were intended to offer good value for the price while still providing excellent reliability and temperature stability.
In 2009, Torrey Pines Scientific released the EchoTherm SC20XR and SC20XT digital orbital mixing chilling/heating dry baths. These instruments offered extended temperature range and power and were able to move from one temperature to the next more quickly than previous models.
In 2010, Torrey Pines Scientific released an entire line of Peltier-driven, compact chilling/heating dry baths with one or two chilling/heating positions and an interface for use with robotic systems. These units were particularly well-suited to the molecular biology lab for performing hybridizations, sample prep for PCR, ligations, and enzyme reactions.
Also in 2010, Lab Armor, manufacturers of lab beads, introduced a new bead bath designed solely for use with beads rather than water. This water bath delivered temperature uniformity while completely eliminating water, which is known to be a major source of contamination in laboratories. Because it relied on beads rather than water, the bead bath could be used for containers that are not watertight, and could hold samples.
In 2011, Grant Instruments expanded its Aqua range of unstirred water baths by introducing the GLS Aqua Plus series linear shaking water bath, targeted to molecular biologists for applications such as hybridization, producing bacterial culture media, and for solubility studies.
In 2011, PolyScience introduced its latest generation immersion circulator, the MX Immersion Circulator. This instrument occupied a minimum of reservoir space, providing more room for samples and glassware. In the same year, PolyScience also launched a line of circulating water baths designed to be both lab- and operator-friendly. Innovative features included a swiveling control head that permits viewing of the temperature display anywhere within a 180° viewing radius, an integral lid docking system for no-mess reservoir cover storage, and a corrosion and chemical resistant top plate that dampens noise and remains cooler at high temperatures.
Finally, in 2011, PolyScience introduced a line of compact and affordable low-temperature chillers, the LS-Series / LM-Series / MM-Series, designed to maximize bench space. These chillers were intended for use with rotary evaporators, jacketed incubators, small reaction vessels, spectrophotometers, chromatography columns, condensers, and other devices that require robust heat removal.
Future of water baths and chillers
In the future, it seems likely that water baths will be replaced more and more frequently by bead baths, which offer a large number of advantages over water baths. The principal advantage is the absence of water, which helps avoid one of the greatest sources of contamination in the laboratory. In addition, bead baths can be maintained at the appropriate temperature even when not being used, do not require vessels to be supported in racks or holders, and can support a much wider temperature range than water. Future innovations are likely to involve the development of new bead formulations that offer even greater temperature ranges and stability. Water chillers are likely to evolve more gradually over the coming years, with the emphasis on creating units able to offer greater energy efficiency and less environmental impact, as well as offering increased temperature ranges and greater stability.