No air balloon is airtight, which means that the air molecules can escape through the surface or leak through the knot. The surface of the balloon is made of latex rubber, which keeps the air in for some time. However, when the balloon is inflated with air, its skin stretches becoming so thin in some places that tiny microscopic holes appear. Air molecules are able to slowly escape or diffuse via these holes in the surface of the balloon even while the mouth of the balloon is tied in a knot.
Why does air leak out of a balloon?
