Why Does Your Finger Sweat on Glass?

Have you ever noticed how your finger sometimes slides too easily across a tablet screen? It feels like it is sweating. This happens because there is always a very thin layer of water between your skin and the glass. Your fingertips have tiny pores that release moisture, even when you do not feel hot.

This water acts like a slippery slide. When the layer gets too thick or uneven, the force that helps your finger grip the surface weakens. Think of walking on wet tiles compared to dry ones. If there is just right amount of moisture, it feels good. If there is too much, you slip.

Screen makers work hard to balance this. They adjust how sensitive their screens are to touch so that a little bit of sweat does not confuse the device. Newer glasses also have special coatings that repel oil and water slightly more than before.