Mordant gilding or oil gilding.
Among the various techniques used for the gilding of a painting, the oil technique involves the use of an oleo-resinous mordant to allow the adhesion of the gold leaf. Oil is the term that identifies this mordant.
French: Dorure à la mixtion – Italian: Doratura a missione – Spanish: Dorado in mixtion – German: Mattvergoldung
The oil or “mordant” gilding technique appears to have already been described by Cennino Cennini and widely used in painting between the Fourteenth and Fifteenth Centuries.
Compared to the more known and appreciated water gilding the technique involves the use of a “mordant”, that is a rather dense oleo-resinous adhesive, instead of the Armenian bole.
The mordant is applied with a brush on the areas where the gold must adhere, the leaf is placed and lightly pressed after the adhesive has started to be sticky. The excess gold leaf is then easily removed by dusting the surface.
The brightness of an oil gilding is always lower than that of a good water gilding, also and above all due to the impossibility of burnishing the treated surface. However, the technique has been widely used to gild surfaces of limited extension and to obtain decorations and finishes of the painted parts thanks to the relative ease of the procedure.