Color- and form-labeled particles of Optosil (version 1980, a silicone rubber, Bayer, Leverkusen, Germany) have been used previously to quantify the underlying processes of food comminution, i.e., selection and breakage, in subjects with normal dentitions. The aim of this present study was to develop a weakened Optosil that is suitable for the study of selection and breakage in subjects with impaired chewing ability. Half cubes (4.8×9.6×9.6mm) were subjected to load tests to determine the force, deformation and work at particle fracture for periods of up to 6 months. Methods of modifying Optosil were (1) heat-treating the base material to produce "Optosoft"; (2) mixing the base of Optosil or Optosoft with a nonprescribed catalyst (Verone, Davis Schott Lander & Davis Ltd, Herts, England) to produce "Optoweak" or "Optosoft-weak" and (3) heating half cubes that were preweakened. A weakened and stable test food that is suitable for labeling and reuse has been obtained by color-dyeing the Optosoft base and using Verone ("dyed-Optosoft-weak").