Electron Spin Resonance is used to determine concentrations of free radicals in foods and materials. In the beer industry it is invaluable as a measure of how prone the beer is to “staling” where beer-derived free-radicals ultimately result in the production of carbonyl end products that result in the distinctive “off” flavor of old beer. In the orthopaedic industry free radicals are induced by the crosslinking, or other manufacturing process, and therefore tracking these radicals is critical for determining ultimate stability of the materials. CPG’s acquisition of an ESR, along with the extensive calibration and validation we have performed, provides a valuable tool in determining likely stability of materials.