Gold leaf glue, also known as gold size, is a type of adhesive used in the process of gilding, which involves applying a thin layer of gold leaf to a surface. Gold leaf glue typically consists of a mixture of a binding agent, such as rabbit skin glue or gelatin, and a solvent, such as water or alcohol. The purpose of gold leaf glue is to create a tacky surface that allows the gold leaf to adhere to the object being gilded. The glue is usually applied in a thin layer using a brush, and then left to dry until it becomes tacky to the touch. Once the gold leaf is applied to the tacky surface, it adheres firmly, creating a shiny, metallic finish.