PURPOSE: To convert a coating into silicon dioxide-containing ceramic by coating a substrate with a hydrogen silsesquioxane resin to deposite a preceramic coating and heating the coating in the presence of ozone.

CONSTITUTION: The substrate is coated with a soln. comprising 0.1 to 25 wt.% hydrogen silsesquioxane resin and a solvent such as n-heptane or toluene. The solvent is evaporated at an ambient temp. or at a high temp. to deposit the preceramic coating on the substrate. The preceramic coating is heated at a temp. within the range of 40 to 400°C for 8 to 10 hours in the presence of ozone to convert the preceramic coating into the silicon dioxide-containing ceramic and to attain planation. Ozone can be conveniently generated by exposing oxygen to a UV light source.