Traditional or “true” gesso is a hard, inflexible and exceptionally absorbent painting ground made from powdered mineral whiting (chalk or gypsum) combined with a water-based, protein (hide) glue. It is the historic painting ground for egg tempera, and not to be confused with acrylic dispersion products of the same name.
Gilding is any decorative technique for applying fine gold leaf or powder to solid surfaces such as wood, stone, or metal to give a thin coating of gold. A gilded object is also described as "gilt". Many egg tempera artists throughout history (particularly in the religious icon-writing tradition) have gilt portions of their panels.
Glazing is a painting technique whereby relatively thin, transparent layers of paint are applied on top of existing layers, allowing the underlying layers to show through.
Scumbling is a painting technique whereby opaque paint (primarily white or tinted white) is applied on top of existing layers so thinly that it behaves semi-transparently, to soften, lighten or otherwise modify the underlying layers.