Agate burnishers are used at the conclusion of the gilding process, to rub the gold leaf to a bright shine. Agate is a smooth stone; this agate burnishing stone is set into a handle. This tool creates the bright mirror finish when used to rub the dried gilded surface. Experts simply tap the gesso with the burnisher and listen to the sound to tell whether it is ready. Note that if there is dampness in the gesso, that the agate will rip the surface instead of polishing it. Bear in mind that re-burnishing after a few days will usually heighten the gloss. For flat areas the larger the agate the better.
