Cover the top of the beaker with a piece of cheesecloth.
Drain off the vinegar and whey over a sink.
Carefully remove the cheesecloth and collect the curds (casein) in the cheesecloth. Rinse the cheesecloth containing the casein in cool water and squeeze the cheesecloth until the casein is almost dry.
Spread out the cheesecloth to let the casein dry for a few minutes.