Undulations / Buckling / Wrinkling / Cockling:

Uneven deflection of a flat surface of usually flat 2 d materials such as mats, textiles, barkcloth, canvas paintings, paper and vellum.

Unstable:

Object has sustained significant amounts of damage making its structure unstable or with extensive losses or breaks and is at risk of further damage.

Unsupported paint ledge:

Where gesso or material underneath paint layer is eroded away leaving jutting paint layer.