Draining liquid from a mixture on Shabbos

Hi,

On Shabbat, one may pour liquid out of a container which holds both solid and liquid in an attempt to get rid of the liquid, and one may use the lid to hold back the solid from falling out, so long as one leaves some liquid in the container. This is not a prohibited act of boreir [ "separating"], because the mixture yet remains.

(Rav Moshe Feinstein, Igrot Moshe Orach Chaim 4:74:Boreir 1)

המצפה לישועה,
Mordechai