Glair, or White of Egg was used in Medieval and Renaissance art, as a binder for paint in illumination, gilding, and even as a varnish. 

Cennino Cennini provides a recipe and multiple uses for it in his book, Il Libro dell’Arte, A Craftsman’s Handbook, written in ca. 1390 – 1437.

I use Cennini’s glair often in the studio.  It is incredibly useful for historical painting and gilding projects. 

Glair Recipe

1. Seperate egg whites. 

2. Beat the whites thoroughly to a good, solid foam until you have stiff peaks.  I do it by hand with a fork or a whisk. It takes about 10 minutes. 

3. Leave the foam to distill overnight. 

4. In the morning, the clear liquid at the bottom of the bowl is glair. Simply toss the foam away, and strain if necessary. Store the glair in a jar with a lid.  It will start to smell,  but is known to work better over time.