The surface tension of a liquid is determined by its chemical composition and its temperature. The following applies: The higher the temperature the lower the surface tension. Therefore it is important to indicate surface tension measuring values with the corresponding liquid temperature.
If measuring the surface tension of liquids containing surface active components (surfactants), the measuring values are also dependent on the measuring method. The parameter ‘surface age’ is especially important for dynamic methods.
For many technical liquids (not containing surface active components) the surface tension in dependence of the temperature is indicated as follows (Dean, J. A.: Lange's Handbook of Chemistry.14. Aufl.; Mac Graw-Hill. Inc., New York 1990):
‘surface tension = a – b * temperature’
Examples:
| Liquid | Surface Tension (20 °C) |
| Water | 72,7 mN/m |
| Glykol | 47,7 mN/m |
| Chloroform | 27,2 mN/m |
| Ethanol | 22,4 mN/m |
| IPA (Isopropanol) | 21,3 mN/m |
The temperature dependent surface tension of water is described by a formula after Teitelbaum (T in °C):
surface tension = 75,69 - 0,1413 * T - 0,0002985 * T²
Examples:
| °C mN/m | °C mN/m | °C mN/m | °C mN/m |
| 0 75,7 |
25 72,0 |
50 67,9 |
75 63,4 |
| 5 75,0 |
30 71,2 |
55 67,0 |
80 62,5 |
| 10 74,3 |
35 70,4 |
60 66,1 |
85 61,5 |
| 15 73,5 |
40 69,6 |
65 65,2 |
90 60,6 |
| 20 72,7 |
45 68,7 |
70 64,3 |
95 59,6 |
Water is used to calibrate the SITA tensiometers. Based on the known surface tension of water it is very easy to test a successful calibration and to decide if another calibration is necessary.
