The transparent white part of the chicken egg. Compared to egg yolk, it is much less suitable as a binder for the preparation of tempera: Due to the absence of oils and fats, it tends to form a brittle and sometimes water-sensitive film. Nevertheless, it was used in ancient times as a binder for lean tempera (it has the advantage of being colorless), for inks, and to thin the fireclay in gilding. It was also used as a final varnish, as documented by Cennino Cennini (late 14th century) and Filippo Baldinucci (1681), among others. It is used, among other things, as a binder and adhesive for so-called shell gold (powdered gold leaf) and for the poliment or bolus layer under gilding.