Alfa-Laval cream separator, 1938.
© Science Museum / Science & Society Picture Library
Sectioned model. Cream separators work by spinning the milk very rapidly, so that the heavier part of the milk is spun away from the centre with a greater force than the cream, which is les dense. The two parts can therefore be separated. A similar kind of centrifuge is used in laboratories to separate the heavier red cells from the lighter plasma in blood.