The pit does not have any magical properties. What turns the guac brown is the air. If you can keep air from touching the guac then it will stay green. The pit will keep a portion away from the air, but what is more affective is to put plastic wrap over it and push it right down onto the surface.
Denuded skin is just another way of saying that the top layer (epidermis) of skin is gone...either from friction (abrasion or tear), trauma (tape burns), or severe rashes, or from a stage II pressure ulcer.
That's not what we want. So let's suppose that only some of the liquid evaporated and that there are both the liquid state and the gas state present in the box. The gas that is above the liquid is called its vapor and it creates a pressure called vapor pressure. What I mean is this: suppose you put a gas-pressure measuring device into the gas and never touched the liquid.