When the discussion turns to temperature sensing, thermocouples get most of the attention. For determining surface temperature, however, especially when the surface may be moving, rotating, or inaccessible, no high-tech instrumentation outperforms phase change indicators.

The drawbacks to electrical or electronic instrumentation include vulnerability to external factors such as static electricity, ionized air, humidity , and being dropped. Electronic devices also require trained operators with technical understanding and skill. Remote-reading infrared sensors present fewer problems but still need skilled operators.

Phase-change temperature indicators, in contrast, take advantage of precise melting points of different materials and are easy to use. Tempil's phase-change temperature indicators are made of materials with melting points calibrated to a guaranteed accuracy of 1%. There are more than a hundred temperatures between 100 and 2500F (38 to 1,371C) available to be chosen. The indicators do not read out an exact temperature. But by melting they let users know exactly when a preset minimum or maximum has been reached.

Phase-change indicators react within milliseconds, unlike thermocouple or probes that must reach equilibrium with the surface and have to compensate for heat conducted away from the region being tested. Phase-change materials, on the other hand, are in intimate contact with the surface being measured, and only need someone who can see that a dry chalk mark has melted or a label changed color.

Other advantages include no set-up, calibration or recalibration periods. They are also relatively immune to abuse, unlikely targets for pilferage.