Britannica Sources used in this answer

Why should conservators avoid sealing a damp wall painting with impermeable coatings?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Inside the ongoing preservation of the Vatican — Art conservation and restoration Learn about the restoration of tiles in St. Peter's Basilica, Vatican City.

In the field of art conservation and restoration, conservators must avoid sealing damp wall paintings with water-impermeable coatings, such as wax or resinous products.

The primary reason for this is to ensure that moisture can continue to evaporate freely from the surface. If these evaporative sites are blocked by an impermeable barrier, the trapped dampness cannot escape through the front of the painting. Consequently, the moisture is forced to move laterally within the wall structure, which expands the areas of damage and can lead to further deterioration, such as the delamination of paint layers or the formation of mold and mildew.1

By allowing the wall to "breathe," conservators prevent the accumulation of moisture behind the paint surface, which is essential for maintaining the structural integrity of the artwork and its substrate.1