Grape crushing is essentially harvesting grape tears right? Ok, so that's probably a bit off the mark, but to understand why wine 'cries' or has 'legs' this YouTube video gives a far better explanation. It's pretty neat stuff. Also, surface tension plays a huge role in the quality of your final clean - just to tie it back to what we do best, that's why we add surfactants to our many of our cleaning products to assist with the final clean. But that's another story!