Just for fun, I used to play around with liquids, and I noticed something odd. In an uncovered tall glass container, ~20 fl.oz., I made an emulsion of water and olive oil by mixing and blowing bubbles with a straw. (Go ahead, laugh.) I let this sit undisturbed on a window sill for a while and checked it periodically to observe the oil and water separating. But sometimes, little drops of oil would remain stuck to the side of the glass and not float above the water. I would let this sit for a very long time, and after all the other oil had separated, these drops would still remain stuck to the glass. Does anyone know how this happened?