The detachment of wall paintings involves the removal of a wall painting from the structure of which it formed part. Once a common practice, with the move towards preservation in situ, detachment is now largely restricted to cases where the only alternative is total loss. According to the International Council on Monuments and Sites, "detachment and transfer are dangerous, drastic and irreversible operations that severely affect the physical composition, material structure and aesthetic characteristics of wall paintings. These operations are, therefore, only justifiable in extreme cases when all options of in situ treatment are not viable."
In their study, Mora, Mora, and Philippot cite four reasons for the "over-use" of detachment: the 19th-century division of the arts that privileged a "painting" divorced from its architectural and historical context; insensitivity to the aesthetic consequences, often partially concealed by restorers; the curiosity of art historians looking for sinopie; or perceived savings relating to the initial cost of treatment. Commercial gain and exploitation as consumer goods by collectors, dealers and restorers provides another possible incentive. This process enables nowadays' companies to offer their customers an authentic fresco, created in their laboratory according to the ancient technique and transferred onto a canvas to be shipped to the place of installation.
Changing values
As the values of a society change, so to does its attitude towards works of the past.
Techniques
There are three main methods, typically referred to by their Italian terms, namely stacco a massello, involving detachment and removal of painting, render, and some or all of the mural support; stacco or detachment of the painting with render alone; and strappo, lit. "tearing", lifting of only the paint layer, attached to a facing with adhesive. In each case the resulting material must be applied to a new support.
Criticisms
Minimum intervention and reversibility are core conservation ethics that favour preservation in situ. Detachment breaks the intrinsic link between wall paintings and architecture; causes irreversible physical damage to the texture, topography, and tone of the painting; leaves a void in the stripped interior; with the introduction of new materials, typically leads to a cycle of retreatment; and has resulted in "many transfers in terrible condition that serve as examples of serious, albeit unintentional, maltreatment".