Photochromic coatings including silver halide microcrystals were formed on a glass substrate via the sol-gel process. 3-Glycidoxypropyltrimethoxysilane and methyltrimethoxysilane were used as starting materials of the ormosil matrices. The 3-chloropropyltrimethoxysilane and bromophenyltrimethoxysilane were added as halogen sources and silver colloidal dispersions were introduced into the precursor solution. The precursor solution was applied using a spin-coating process on a silica buffer layer which prevents Ag+ migration into the glass substrate. The coated glass became transparent and photosensitive after Ag(Cl1-xBrx) microcrystals were precipitated in the coatings above 300 degreesC. However, fading reaction did not proceed at room temperature. It was found that the deposition of a sensitizing layer including cuprous ions on the photosensitive laver was very effective in promoting fading reaction at room temperature. The cuprous ions in the sensitizing layer penetrated and diffused into the photosensitive layer during coating and firing. The cuprous ion located near or in the Ag(Cl1-xBrx) microcrystals acted as an effective sensitizer.