The invention relates to thermally tempered safety glass comprising an non-abrasive and porous SiO.sub.2 layer which is stable during sintering and has a refractive index of between 1.25 and 1.40. The inventive safety glass can be obtained by coating standard soda-lime glass with an aqueous coating solution having a pH value of between 3 and 8 and containing between 0.5 and 5.0 wt. % of [SiO.sub.x(OH).sub.y].sub.n particles (0