Despite this busy engagement with large works of public architecture, Bernini was still able to devote himself to his sculpture, especially portraits in marble, but also large statues such as the life-size "Saint Bibiana" (1624, Church of Santa Bibiana, Rome). Bernini's portraits show his ever increasing ability to capture the utterly distinctive personal characteristics of his sitters, as well as his ability to achieve in cold white marble almost painterly-like effects that render with convincing realism the various surfaces involved: human flesh, hair, fabric of varying type, metal, etc. These portraits included a number of busts of Urban VIII himself, the family bust of Francesco Barberini and most notably, the Two Busts of Scipione Borghese—the second of which had been rapidly created by Bernini once a flaw had been found in the marble of the first. The transitory nature of the expression on Scipione's face is often noted by art historians, iconic of the Baroque concern for representing fleeting movement in static artworks. To Rudolf Wittkower the "beholder feels that in the twinkle of an eye not only might the expression and attitude change but also the folds of the casually arranged mantle".