The first restoration of the chapel frescoes was in 1481-1482, by Filippino Lippi, who was also responsible for completing the cycle. Due to the lamps used for lighting the dark chapel, the frescoes were relatively quickly coated in dust and dirt from the smoke. Another restoration was conducted at the end of the 16th century. Around 1670, sculptures were added, and the fresco-secco additions were made to the frescoes, to hide the various cases of nudity. Late 20th century restoration removed the overpainting and collected dust and dirt. Some critics, including professor and art historian James H. Beck, have criticised these efforts, while others, including professors, historians and restorers, have praised the work done on the chapel.