Bentonite

[Thomas]

Jumpshot, there is an old tale that turns out to have merit: one should rack with the sight of the full moon, or on a clear day. Seems that low pressure atmosphere keeps micro-particles in suspension easier than high pressure atmosphere. It isn't a problem for large volume, but for home winemaking it could make a difference in the success of the racking.

The reason for racking is to remove the liquid from the stuff that settles at the bottom. When you start the racking with a syphon you invariably stir up some of the particles back into suspension. High pressure might help them fall back to the bottom quick. Can't hurt!