Why can excessive heat and pressure during canvas lining damage a painting?

In the context of art conservation and restoration, the process of lining—reinforcing a canvas by attaching a new one to the back—carries inherent risks if not performed with extreme skill.

When using techniques such as the vacuum hot table, excessive heat and vacuum pressure can cause significant damage to a painting by drastically altering its surface texture. Furthermore, the application of heat and pressure can lead to the penetration of adhesives, which may darken the canvas and cause thinning or damage to porous paint layers.1

Because of these risks, the field has increasingly moved away from wholesale lining treatments. Modern conservation efforts now prioritize more refined, precise, and limited interventions, such as the use of low-pressure suction tables, which allow for the application of controlled heat and gentle pressure to address specific condition problems like tears or paint cleavage without compromising the integrity of the original work.1