A novel write once optical recording medium is one application of a phenomenon reported here: when a thin layer of gold on PMPS-a typical polysilane-is pre-exposed to UV radiation before being heated, a gold colloid is formed in the PMPS in those areas which were exposed to the radiation. The accompanying reduction in reflectance due to the gold-to-magenta color change can be used as an optical memory that is compatible with the current CD reading system. Details of the observation and follow-up studies are reported.