Adhesive or sizing comes in many forms, and all forms share one important property called open time. This is the amount of time that the adhesive stays workable after it has been applied. In most cases, the adhesives used for leafing will allow the artist to apply the adhesive to large areas without having to worry about it drying out before the leaf is applied. Traditional adhesives are oil based, but in recent years, the advancement of water-based adhesives has made them very popular.