Examination and treatment of eight large panel paintings (37.663-64, 37.667-71 and 37.674) led to discoveries into the making of a Gothic altarpiece. Treatment at the museum spanned seven decades, chronicling the changing philosophies of painting conservation in the twentieth century. This investigation reveals a complicated painting technique. A large studio produced the series, oftentimes using incompatible materials and application methods that caused a deterioration pattern, exhibited to some degree on all eight panels. Since entering the museum in the 1930s, all panels have been treated, reflecting shifts in conservation philosophy. By examining these treatments, certain generalizations can be made regarding conservation practices and trends.