Additives belong to a broad and diffuse category of key components in a coating formulation. They comprise a small percentage of the coating formulation their use level rarely exceeds 1 or 2%, and the total level of all additives in a formulation seldom exceeds 5% of the total product. Their impact, however, is significant as they contribute to the ease of manufacture, the stability of the coating in the package, ease of application, quality and appearance of the final film. Additive function is almost always very specific in nature. Some additives are multipurpose; for example, they may be important to the manufacturing process as well as to the coating’s performance. Some additives are proprietary products with highly specific functions that work well in some systems but cannot be used in others. Additives are generally categorized by function rather than by chemical composition or physical type. Because the actual chemical composition of many additives is proprietary, a formulator may run into problems with chemical side reactions.