This paper describes a general method for validating the composition of rubber and plastic compounds. Composition is a critical attribute that influences the performance of manufactured products. The approach described should be of interest to quality control managers, engineers, research and development staff, business professionals and facilities managers. The properties of plastic and rubber materials are influenced by the base polymer components, the fillers and the additives. Commercial plastic and rubber materials can lack ingredients they should contain and can include ingredients that were not an intended part of the composition. Analytical methods that can objectively and independently verify formulation compositions are provided in a case study format.