Glossary · Technique
Glazing
The application of thin, translucent layers of oil paint over completely dried underlayers — each glaze modifies the color and tone of what lies beneath, building depth and richness impossible to achieve in a single paint application.
Definition
A glaze is a thin layer of oil paint — highly diluted with medium (linseed oil, walnut oil, or resin) — that is transparent or translucent enough to let the layers beneath show through. When applied over a lighter underpainting, a glaze darkens and enriches it while allowing the modeling of the underpaint to remain visible. Multiple glazes build up optically — each layer subtly altering what the eye perceives.
Leonardo's Use of Glazing
Leonardo's sfumato technique depends on glazing. Scientific analysis of the Mona Lisa (Centre de Recherche et de Restauration des Musées de France, 2010) identified up to 30 glaze layers in the face and hands, each less than 2 micrometres thick. No single layer is responsible for the final effect; it is the accumulated optical interaction of dozens of translucent films.
This extreme approach — building a painting almost like an optical filter — requires extraordinary patience and technical mastery. Each layer must dry completely before the next can be applied, meaning a single painting might represent months or years of work across multiple sessions.