Maleic/ Fumaric Acid Fortified Rosin is a commonly used sizing agent. The Fortified Rosin improves the quality and life of paper. The Fortified Rosin is fortified with maleic or fumaric acid under suitable condition to form an adduct which acts as a very effective sizing agent. Maleic/ Fumaric Acid Fortified Rosin is available in yellow or brown liquid form with a pH of 9.5 - 10.