Exposing dichromated gelatin holograms to microwave radiation considerably increases their resistance to heating, either for wide or narrowband holograms. No wavelength shift was observed for the former and only a small shift was observed for the latter. This behavior can be explained in the framework of Chang's models, taking into account the effects of microwaves on polar molecules and the potential positions of the water molecules within the medium. These results and their interpretation suggest further experiments to measure the different environments of the water molecules inside the gelatin and to use microwaves at the resonance frequencies of the water.