One morning I was washing dishes in the remnant of our kitchen when destructoBoy came in and sat on the steps. "Muuum.." My blood ran cold. That tone of voice was precusor to the kind of question I haven't dealt with in a while.
Suffice it to say I answered it through example of a black plastic bin bag. Both in its flaccid state.
And when filled with air.
He and his sister were in hysterics by the end of my demonstration.