In the realm of thermometer calibration, there are two primary methods: the ice bath test and the boiling point test:
- Ice Bath Test: This is a simpler and more straightforward method. It involves submerging the thermometer in a mixture of ice and water. The idea is that this mixture, when properly prepared, is reliably at 0°C (32°F). If the thermometer reads this temperature, it’s considered accurate at this point.
- Boiling Point Calibration Test: This test is a bit more complex. It involves immersing the thermometer in boiling water and checking if it reads the boiling point of water, which is typically 100°C (212°F) at sea level.
However, the boiling point can vary based on altitude and atmospheric pressure, making this test trickier and less consistent than the ice bath test. Additionally, since water vapor can interfere with some types of thermometers, this can further complicate the calibration process.
Given these factors, if the ice bath test proves the thermometer is accurate at 0°C, it’s often deemed sufficient for most cooking purposes.
However, if you want to create boiling water to calibrate your thermometer, you need to calculate the boiling point in your place.
How to Calculate the Boiling Point of Water
To calculate the boiling point in your area, you need to know your local pressure and elevation. The boiling point of water decreases as you go higher in elevation because the pressure is lower at high altitudes.
Here are the basic steps to calculate the boiling point where you are:
Step 1: Find your local pressure and elevation on the Weather Underground. Simply introduce your location and look for the details on the page like the example to the right.
Step 2: You can enter your local pressure and elevation, then calculate your local boiling point using a boiling point calculator online tool.
If you want to calculate the boiling point by yourself, you can refer to this formula:
- Boiling point = 49.161 × ln(pressure) + 44.932
- Pressure = 29.921 × (1 – 0.0000068753 × altitude)^ 5.2559
Note that these formulas use specific units: boiling point is in degrees Fahrenheit (°F); pressure is expressed in inches of mercury (inHg); and altitude should be put into the equation in the imperial unit — feet (ft).