Why does titanium feel so good on your skin?
There are many articles in watch magazines and forums--or is it fora?--touting titanium as the metal of choice for wearing comfort. In addition to its light weight and easy-care finish, titanium feels pleasant to the touch, never uncomfortably hot or cold like more popular metals, such as stainless steel and gold.
1. DISPELLING THE MYTHS
Let us first dispel the popular myths. It is not the "temperature" of the metal that causes the different feels. Another popular myth is that titanium keeps your body temperature better than other metals because it has a high "heat transfer efficiency." This explanation is also wrong.
2. THE IMPORTANCE OF SUDDEN TEMPERATURE CHANGES
Indoors, watches are essentially at THE SAME TEMPERATURE--the room temperature. But when you put a watch on your wrist, different metals feel very different on your skin: titanium feel neutral, comfortable; steel and gold cold. Likewise, wood furniture or the carpet feels nice, while the sink or marble floor feels cold. Here is why.
The thermal receptors of our skin respond to steady levels of temperature. But they respond more sharply to sudden temperature changes before fading back, in less than a minute or so, to a control level. It is this stimulated response that dictates how a metal feel on our skin. As we put a watch on our wrist, it quickly draws heat from the skin causing the skin temperature to drop: the metal feels cold.
In a nutshell, it is the sudden temperature change, not the steady temperature, that dictates the thermal comfort.
3. HEAT TRANSFER: WHEN EFFICIENCY IS UNDESIRABLE
ALL metals conduct heat efficiently and reach your skin temperature soon after contact. But stainless steel, aluminum, and gold conduct heat 2, 11, and 15 times more rapidly than titanium, respectively. So, unlike titanium, these metals draws heat very quickly from your skin, causing its temperature to suddenly drop, thus creating the cold feel. Heat transfer efficiency causes thermal discomfort.
Under a bright sunlight or in a sauna, the reverse process takes place. Stainless-steel, aluminum, or gold are such effective heat conductors that they absorb heat very quickly from the surroundings. You feel heat, or even pain as these metals become suddenly hotter than the skin. On the other hand, being a less efficient heat conductor, titanium heats up more gradually thus causing only a mild response from your skin. Also, given more time to dissipate the heat, the skin--and the watch movement--is less likely to overheat or burn.
The most vivid illustration of heat conduction efficiency I recall was given by an engineering professor at the University of Fairbanks, Alaska, where good understanding of heat transfer is essential to your health. He asked the following question: when it is-30°F outside, a common occurrence in Fairbanks, Alaska, and you have to go to the outhouse, what would you prefer to use? A Styrofoam seat or analuminum seat? All his students knew the right answer!
Thus, the most comfortable watch metal is the poorest heat conductor--titanium.