Applied Contact Temperature

We’ve talked before about the contact temperature and the effect that different materials have on the temperature that you feel when you first touch them.  Today we’ll look at that effect in a more applied way.
Recall that the interface temperature can be expressed as the weighted average between the two temperatures of the contacting bodies. The weighting parameter, which I called “m” is defined as:

Now, imagine that you want to protect your fingers from getting scorched, or frozen, when you touch a hot or cold metal surface.  Since metals have a value of “m” that is much higher than the value of your skin, the interface temperature is going to be close to the surface temperature.  However, if you could put a thin coating of some other material that has a value of “m” that is much lower than that of your skin, then the interface temperature would be closer to your skin temperature, and you could protect your skin, at least for the first few moments of contact.

This figure illustrates the general idea for a few materials.  I’ve assumed that the temperature of the surface of your skin is about 32°C.  The horizontal axis shows a range of surface temperatures between -30°C and 110°C.  The vertical axis shows the corresponding interface temperature, that is, the temperature that you would feel at the initial contact.  Pain from heat starts in neighborhood of 50°C and from cold around 0°C.  Those are somewhat subjective, so I’ve shown them with blurry lines.