The burnish-size should be always kept in a china or earthenware jar. If
kept in a tin vessel, its moisture causes the tin to rust, and the
deposit caused by the rust is highly injurious to the size. The oil-size
may be kept in a tin vessel provided with a cover. When this size is
required for use, it should be thoroughly stirred up, as the coloring
matter of which it is in part composed, being the heaviest, has a
tendency to settle and to leave the pure oil on the surface. Take out
only a sufficient quantity for immediate use, as it sets quite rapidly,
particularly in warm weather; and do not return any that may be left,
back to the original vessel containing the size. Pay no attention to the
skin which from time to time forms on the surface, when not in use.