In 1282 A.H. (1865 C.E.), the Shams-ul-Amara building was commissioned by Naser al-Din Shah Qajar and constructed under the supervision of Dost Ali Khan Moaierol Mamalek in the eastern part of the Tehran Citadel. As the first five-story building in Tehran, Shams-ul-Amara holds significant architectural and historical importance. The plinths of the rooms across its five floors are adorned with oil-painted tile decorations, executed in a predominantly European style. These paintings were created by a group of artists and their students, as evidenced by variations in
their execution techniques. The method of oil painting on glazed tiles was a unique innovation that was not replicated in subsequent architectural projects. However, these paintings are now experiencing extensive deterioration, including disintegration, pulverization, and collapse. This article aims to identify and analyze the factors contributing to the damage of these oil-painted tile artworks. It is hypothesized that the varying degrees of damage observed on each floor are influenced by differences in the tiles' placement, the composition of the lining materials, the application methods, and other mechanical and environmental factors. Additionally, the prolonged exposure of these tiles to moisture absorption from the walls, combined with the tension caused by the oil painting technique, has led to physical stress. This stress manifests in the form of paint detachment, separation of relief patterns along tile seams, and breakage at the corners of rhombus-shaped tiles installed on the walls. This study employs a descriptive-analytical approach, with a focus on the lining layer as the most critical factor in the deterioration process. The findings suggest that the lining layer fails to adequately protect the painted surface, leading to the eventual collapse of the paint layer.