Silsesquioxanes containing β-acetoxyethyl (BAE) groups are processible resins that can be employed as spin-on-glass precursors to dielectric silica films. Thermal treatment >250 °C results in extrusion of ethylene from the CH2CH2OCOCH3 moiety with formation of Si- OCOCH3 groups, which undergo facile hydrolysis to a silica network. A minor pathway involving extrusion of acetic acid leaves some silicon vinyl groups, leading to residual organic carbon in the material. However, addition of a fluoride ion catalyst greatly accelerates the major reaction, resulting in lower conversion temperatures (<200 °C), quantitative extrusion of ethylene, and essentially pure silica. Alternatively, BAESSQs can be processed photochemically (λ <200 nm) to cleanly yield silica at ambient temperature.