How to choose a dry bath
A dry bath is also called a metal bath，is a commonly used laboratory device for constant-temperature heating. It employs an electric heater to warm a metal block made of high thermal conductivity material, which is designed with multiple precisely machined wells. By means of heat conduction, the instrument provides uniform heating or incubation for sample tubes inserted into these wells.
Dry Baths vs Water Baths
| Feature | Water Bath | Dry Bath |
| Heating medium | Water (or silicone oil) | Metal block (e.g., aluminum, silver alloy) |
| Temperature range | RT ~ 99 °C | RT ~ 150 °C |
| Heating rate | Slow | Fast |
| Capacity | Large-volume samples (measured in L) | Small-volume, fixed samples (measured in mL) |
| Special applications | Volatile, toxic samples and large-volume solutions | Samples sensitive to water vapor or prone to contamination |
Common Application Scenarios
PCR experiments
Enzymatic reactions
Protein processing
Microbiology experiments
Cell culture
Heat-shock transformation
How to Choose a Reliable Dry Bath for Your Lab? These 6 factors help you make choices faster
Definition
The range of temperatures that the device can reach and maintain stably.
Cooling Function
Without cooling function: The lower limit typically does not start from 0°C, but from slightly above ambient temperature (e.g., RT + 5°C).
With cooling function: The lower limit can start from 0°C or even reach -10°C.
Cooling
>100°C
Definition
The deviation between the displayed temperature and the actual average temperature inside the block.
For example, ±0.5°C accuracy means that when the display shows 100.0°C, the actual temperature ranges from 99.5°C to 100.5°C.
Existing deviations
High-precision sensors such as Pt100 platinum resistance are commonly used.
The actual sample temperature also depends on how closely the tube walls fit the metal wells. Poor contact can lead to significant differences between the metal block temperature and the sample temperature, even if the block itself is highly accurate.
Temperature Uniformity
Definition
The variation in temperature across different points within the working area.
For example, ±0.1°C uniformity indicates that the temperature difference between any two points in the block does not exceed 0.2°C.
Comparison between Water Bath and Dry Bath
Water Bath (Macro uniformity)
Relies on water circulation and convection (especially with Circulators). Continuous water flow quickly exchanges heat throughout the bath, achieving highly uniform temperature in the entire vessel.
Dry Bath (Local uniformity)
Relies on the high thermal conductivity of the metal block. Heat is quickly conducted from the heating element to the entire block. Within a single well, the sample is heated very evenly due to tight contact between the tube and the well. However, slight temperature differences may exist between different wells due to distance from the heat source, machining tolerances, or heat loss.
Guideline: Use a dry bath for small-volume, locally controlled experiments; use a water bath for large-volume applications requiring stirring or solution homogeneity.
≤±0.5℃
≤±0.3℃
Heating Rate
The speed at which the device reaches the target temperature (°C/min).
1.Fast heating (from RT to high temperature)
| Start Temperature | Target Temperature | Typical Application |
| Room temp (~25°C) | ~95°C | PCR pre-denaturation, hot start |
| Room temp (~25°C) | ~65–72°C | PCR extension step |
| 4°C (from fridge) | ~42°C | Bacterial heat-shock transformation |
| Room temp (~25°C) | >70°C | Enzyme inactivation |
2.Slow heating
| Start Temperature | Target Temperature | Typical Application |
| 30°C | ~42°C (gradual) | Induction of certain prokaryotic protein expression |
| Specific low temp | Specific high temp | Materials science, chemical synthesis research |
| Start Temperature | Target Temperature | Typical Application |
*Requirement for device: High-end dry baths or professional temperature controllers should allow programmable ramp rates, i.e., adjustable °C/min heating.
Programmable parameters typically include
1.Target Temperature (Set Temperature): The desired temperature for this program segment.
2.Heating Rate (Ramp Rate): The rate at which the device rises from the starting temperature to the target temperature (°C/min). Slow ramps protect sensitive samples, fast ramps save time.
3.Hold Time / Dwell Time: Duration to maintain the target temperature, in minutes or hours.
4.Next Temperature (Optional for multi-step programs): Automatically switch to the next target temperature and ramp rate.
