Decoration of gold surfaces by punching and incising
Once the gilded background surfaces had been burnished to create a high polish it could be decorated with elaborate motif punches and patterns of incised lines. The textured surface produced by this punching (fig.1) creates a different effect from the decoration produced by the freehand patterns of incised lines (fig.2).
Such decoration, whether by punching or incising, differentiated the haloes from the gilded background. Halos would be inscribed on the gold surface using a compass or dividers to ensure an accurate circle was produced; sometimes the hole left by a compass can still be seen in the surface.
An incised pattern would be made by indenting decorative lines into the gold background with a metal stylus; for example, a small free-hand incised pattern can be seen in the halo of the crucified Christ in the Daddi tabernacle, although this halo also has a simple punch decoration as well. To create a punched decoration in gilding, the metal punch is held at right-angles to the surface and then tapped with a hammer. Provided the gesso ground is still flexible, the punching should just indent it without breaking the gold leaf. Skill is also required in achieving a consistent depth of indentation.
