Each book of gold or metal leaf contains 25 leaves that measure 140mm x 140mm. 1 book of gold will cover an area of 0.4m² without waste or overlap. (The amount of waste can be determined by the gilder’s own level of expertise and will depend on the complexity of the surface being gilded.) The higher the gold content of a leaf the more durable it will be. For outdoor work it is advisable to only gild using leaf that 23ct or higher to avoid tarnishing.