Detachment of wall paintings

[1] According to the International Council on Monuments and Sites (ICOMOS):[2] Detachment and transfer are dangerous, drastic and irreversible operations that severely affect the physical composition, material structure and aesthetic characteristics of wall paintings.

The application of a covering layer concealing an existing decoration, carried out with the intention of preventing damage or destruction by exposure to an inhospitable environment, should be executed with materials compatible with the wall painting, and in a way that will permit future uncovering.Vitruvius records how in Sparta, in 59 BC, "paintings have been taken out of certain walls by cutting through the bricks, enclosed in wooden frames, and brought to the Comitium".

[3] A century later, apprised of paintings of Atalanta and Helen without drapery and "enflamed with lust", Caligula attempted to carry them off, but was prevented by the makeup of the plaster.

Prior to the Napoleonic Expeditions in the early 1700s chemists and architects from around Europe began working with both the strappo and stacco methods of detachment.

[12] 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.

"[19] According to the Benozzo Gozzoli Museum, Castelfiorentino, Italy, the "Strappo" technique is the least invasive method of wall painting removal because unlike stacco a massello or stacco, it "involves removal of only the topmost layer of plaster, which has absorbed the pigment" as described in the video, The Strappo Technique produced by the Museo Benozzo Gozzoli.

[20] Ths video details removal by the strappo method, in which the overlaying painted surface is first coated with a thin layer of cotton cloth and animal glue.

Due to a series of strong earthquakes in the Fruili Region of Italy in 1976, the structure of the Church of San Lorenzo was compromised, posing a severe threat to the integrity of its wall paintings.

[21][22] 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".