We demonstrate a method of synthesizing K2SiF6:Mn4+ red phosphor by wet chemical etching. The starting materials used are silica glasses (fused quartz, borosilicate, and soda-lime glasses). The red phosphor emitting at lambda similar to 630 nm is synthesized by inserting the silica glasses into a HF/KMnO4 solution at room temperature. The photoluminescence and photoluminescence excitation spectroscopy show no clear difference in the spectral feature between the glass-synthesized phosphor and the single-crystalline Si wafers.