How to wear your halo

In Francesco del Cossa's painting of The Annunciation now in the Old Master Gallery in Dresden, the Angel Gabriel is clearly wearing a halo which is visibly attached to his head by a metal frame. Starting with this idiosyncratic detail, we will explore the painting as a whole, putting it in the context the theatricality of the Ferrarese 'school' of painting - of which Francesco was one of the leading members - and discussing it's relationship to other remarkable halos in art. We will also look for parallels for one of it's iconographic oddities: a snail, crawling nonchalantly across the pavement on which Gabriel kneels...