Why do certain materials/surfaces always feel ‘cool to the touch’ at room temperature (like glass/granite)
In: Physics
Our bodies produce more heat than they need, and so are constantly venting heat to the atmosphere. Your sense of how hot or cold something is is less based on absolute temperature and more based on how quickly heat is drawn away from your body.
Air is a poor conductor of heat and has a low heat capacity, meaning it doesn’t draw heat away from your body and itself heats up relatively quickly (further slowing the heat draw). Granite, glass, water, and other materials, conversely, can absorb a lot of heat, and do so very quickly. Even if granite is the same temperature as air, it will absorb a lot more heat, and faster, than air can, so it feels cooler to you (because it’s actually cooling your skin down faster).
These materials have a higher heat capacity than “warm to the touch” materials like wood.
Your body doesn’t actually sense temperature, it senses heat flow. When you touch a granite object the granite doesn’t warm very fast (high heat capacity) so you detect a high heat flow => cold. When you touch a wood object that’s at exactly the same temperature, you warm the outer layer of wood, which is insulated from the rest of the mass by trapped air (low heat capacity) so you detect a low heat flow => warm.
It’s a matter of conductivity.
Cardboard in a freezer doesn’t feel as cold as metal in a freezer, although they are the same temperature.
So, the perception of cold is actually how quickly a material can conduct your warmth from you.
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