The effects of treatment by restorers and the concepts of the dealers, art historians, connoisseurs, or museum persons who employ the restorers are discussed. A work of art is an extraordinary combination of material and immaterial content which are inseparable evidence of the intent of the artist. Incompatible or transitory materials and unpredictable environmental effects contribute to changed surface appearance. Scientists, art scholars, and restorers should ideally work together to make deductions and decisions about how the painting should look. See also AATA 21-1928. -- AATA