Abstract: Photosensitively opacifiable glasses requiring very short exposures to ultraviolet radiation to effect the development of opacity are processed by heating to nucleate Ag followed by cooling to nucleate NaF on the Ag followed by heating to grow the NaF. The glasses contain, expressed in terms of weight percent on the oxide basis, about 14-18% Na.sub.2 O, 0-6% ZnO, 6-12% Al.sub.2 O.sub.3, 0-5% B.sub.2 O.sub.3, 65-72% SiO.sub.2, and 0-0.2% Sb.sub.2 O.sub.3, and 0.007-0.04% Ag, 0.008-0.05% CeO.sub.2, 0.7-1.25% Br, and 1.5-2.5% F as analyzed in the glass, the sum of those components are at least 90% of the total composition.