Measuring the melting interval to determine counterfeit beeswax

Introduction:
Waxes, unlike substances consisting of identical molecules (e.g., water) or identical atoms (e.g., pure metals), do not have a fixed, defined melting point.
Put simply: If we have ice with a temperature below 0°C, the water molecules move but still stick together. At 0°C, the movement becomes so strong that the water molecules stick together less tightly. The water becomes liquid.
However, if you have a mixture of different molecules, as with waxes, then as the temperature rises, the smaller molecules begin to move more vigorously and become liquid. The larger molecules need more energy to move accordingly and therefore only melt at a slightly higher temperature. This means that melting begins at a temperature X and ends at a higher temperature Y. This gives you a melting interval of X - Y °C (melting range).

If we want to determine the melting point of water, we need a thermometer and only need to read the temperature at which water and ice are present simultaneously. The water/ice system must be in thermal equilibrium. Example: If you throw a few ice cubes into 20 °C water and measure the temperature, you will not measure the melting point. This system is not in equilibrium. It takes time for thermal equilibrium to be established. What would happen? The ice melts and the temperature drops, for example, from 20 to 10 degrees Celsius. As you add more and more ice, you get closer and closer to the melting point. Once the melting point is reached, the temperature stops falling. Once the water-ice mixture is in thermal equilibrium, the temperature remains at 0°C until all the water has turned to ice. Only then does the temperature drop below 0°C.

Determining the melting interval for waxes is more complicated. Depending on the amount of wax used, the measurement takes between 30 and 90 minutes.

The measurement requires a pot of melted wax, a digital thermometer (the tip of which should be in the middle of the wax, Fig. 1), a stopwatch, and paper and pen for recording the data. You can also enter the data directly into a spreadsheet program (e.g., Microsoft Excel) and then create and print the corresponding time-temperature curve (cooling curve) as a scatter plot.

Measuring the melting range of pure beeswax:
The thermometer must not have an automatic shut-off function to avoid interrupting the measurement. The battery should not run out during the measurement, causing the device to shut down. If the measurement goes wrong, it can always be repeated. This allows the wax to liquefy again and cool down while measuring the temperature at regular intervals. The temperature is measured every 30 seconds and recorded. The more points you measure, the more accurate the subsequent evaluation will be. Whether you start at 80 or 75°C is unimportant. You only need the temperature data around the melting range. The larger the wax mass, the more accurate the values ​​will be and the longer the measurement will take. Amounts of 150 g - 250 g of wax are sufficient for one measurement.


Fig. 1: Simple arrangement for measuring the melting interval

Melt the wax completely and stir it continuously so that the temperature is the same throughout the wax mass, for example, 75°C. Then remove the pot from the heat source and hang the thermometer in the wax. The tip of the probe should be in the center of the wax.
Now measure the temperature every 30 seconds. Record the time and temperature. There's no need to stir the wax or look into the pot. We determine the melting interval solely from the measured temperature.
After the temperature has reached approximately 60 degrees, the temperature changes only very slightly. The wax has solidified. Stop the experiment and begin the evaluation. For this purpose, create a "time-temperature" dot plot (Fig. 2).


Fig. 2: Dot diagram from time-temperature measurements

In our example, we used Microsoft Excel. Of course, you can also use other spreadsheet programs or, more traditionally, a sheet of graph paper.



Fig. 3: Creating two tangents (red) to the curve

As you can see, the temperature-time curve (cooling curve) forms a curve rather than a sharp bend. To determine the melting range, two straight lines (Figure 3, in red) are drawn along the curve. Once you have drawn the cooling curve on graph paper, you can plot the two straight lines using a ruler and pen. Alternatively, you can print the curve as a graph (Excel) and plot the straight lines.


Fig. 4: Marking points A and B where the red tangents leave the curve.

Now determine the points (Fig. 4, A and B) where the red lines leave the blue curve. Determining these points is not easy.


Fig. 5: Straight lines are drawn from the markings A and B to the Y-axis and the temperature values ​​are read.

To determine the melting range, we draw lines from points A and B to the Y-axis (Fig. 5, dashed lines). We can now read the two temperatures there. In our example, we read the melting range (melting interval) as 61.5–65.5 °C.
The wax data sheet states 61–65 °C. We can see how small the deviation is despite our provisional measurement method.
In principle, the temperature interval (melting interval) can also be determined during heating rather than cooling. However, this is more time-consuming and less accurate, as the pot must be on the heat source, and an even temperature distribution is not guaranteed in a block of wax or in wax pellets – where the wax is already partially melted.

Measuring the melting range of a beeswax-paraffin mixture:
Now, instead of 150 g of pure beeswax, we completely melted 120 g of beeswax and 30 g of paraffin candle wax, stirred, and thus determined the melting range. The result is shown in Figure 6. The melting range decreased to 61-58 °C.


Fig. 6: Determination of the melting interval of a mixture of beeswax and paraffin

Conclusions:
What conclusions can we draw from the result? Deviations from the melting range can be determined using simple means.
Counterfeiters rarely take the trouble to produce mixtures where the melting range matches that of beeswax. They usually choose inexpensive, low-melting paraffins, which then lead to measurable deviations in melting behavior when mixed with beeswax.
Such measurements can be performed not only with mixtures but also with pure paraffins, stearins, etc.
Counterfeits can also be produced using waxes (without beeswax) with yellow dye and beeswax fragrances.
If the "wax" only solidifies at, for example, 50°C, one must measure up to temperatures between 60 and 45°C to determine the melting range.

If you use foundation made of fake beeswax (e.g., with added paraffin), yellow-colored paraffin, or other yellow-colored waxes that melt at low temperatures, the combs in the hive will melt in the summer, depending on the temperature. The losses from the destruction of honey and brood combs, including the colony, are correspondingly high.
With the measurement method shown here, you can at least avoid such losses. If you come across fake beeswax whose melting interval is very similar to that of beeswax, this method will not help.
The probability of obtaining such a fake is likely very low. The advantage would be that the foundation in the hive will not melt at midsummer temperatures. The bees may not notice the difference. It is problematic if chemicals (dyes, artificial fragrances) or other components from the wax migrate into the honey.
Particular attention should be paid to candle making. If you sell beeswax candles that are not made of beeswax or only contain a small amount of beeswax, you must declare them accordingly.
To use this method safely, you simply have to try it out. It is recommended to always measure your own beeswax first as a control and then use the same measuring setup to test the wax you are testing.