This Byzantine church was converted into a mosque in 1577, when the wall-paintings probably received a coat of whitewash. By the 19th century it was in a state of dilapidation, and in 1880 a general restoration was carried out, including removal of loose plaster and general replastering. Much of the wall-painting that remains is covered with chipmarks made to give a key to the new coat of plaster. To remove the 19th century plaster a sculptor's hammer and chisel were used. Removal of the underlying whitewash was mainly by palette knife and, finally, finely-headed dental drills. Other tools were a rotary wire brush mounted on an electric drill, and soft indiarubbers. To secure the original plaster and fill the chip marks a composite plaster of casein, lime, and marble dust was used, with a small amount of sodium pentachlorphenate as fungicide. Powdery paint was strengthened with polyvinyl alcohol. No attempt was made to do detailed restoration. Missing areas in the paintings were toned in such a way as not to be distracting to a visitor while revealing their presence to the scholar. The toning paint consisted of earth colours in bone glue.