Pre-carve burnishing is useful for all except:
Bring further excess mercury to surface
Increase surface hardness
Decrease number and size of voids
Marginal adaptation
Objectives of Precarve Burnishing

Improves the marginal integrity of restoration.
Shapes the restoration according to contours and curvatures of the tooth.
Helps in reducing the mercuric content of amalgam.

Nisha Garg, Amit Garg. Textbook of Operative Dentistry.  Edition 3. Page: 341