Cleaning of Wall Paintings and Architectural Surfaces by Plasma

Abstract

Coating surfaces with a protective layer is a common method to protect artwork from deterioration. These layers consist often of organic substances such as acrylic resins. Due to weathering and ageing polymers usually suffer changes in optical properties and these organic coats also reduce the water‐permeability of porous systems which can cause an accelerated decay. Therefore, we need a method to remove organic matter without harming the substance. In the present study, cleaning procedures with different types of artificially soiled surfaces were carried out. Two different atmospheric pressure plasma jets that permit an economic application were investigated to get the optimal plasma parameters for cleaning.

Assessment of plasma torches as innovative tool for cleaning of historical stone materials

“…These competitive processes turned out in a partial removal of the coating from the stone surface and a contemporary penetration of short polymer chains inside the stone due to the thermal effect of the plasma. This hypothesis is also confirmed by literature data on plasma removal of Paraloid B72 [50]. Paraloid B72 was easily removed from a compact stone surfaces using the Blaster/Tigres, because the low porosity did not allow the penetration of soften polymer favouring its chemical and thermal deterioration induced by the plasma.…”

“…the removal of soot from canvas and marble was tested with one of the first patented atmospheric plasma devices (working at atmospheric pressure instead of vacuum conditions) [26]. Later, atmospheric plasma was tested in the activation of polymeric surfaces in modern art to enhance the adhesion between a non-polar polymer substrate and a polar paint layer [27], and finally, the potentials of a corona discharge and a DBD jet plasma device for the removal of polymers and natural varnishes were explored [28] as well as for the treatment of oxidised metal surfaces or altered by the presence of sulphide [29].…”

Atmospheric pressure non-equilibrium plasma cleaning of 19th century daguerreotypes

“…The laser cleaning process is based on thermal ablation, relying on the different material removal thresholds that characterize corrosion layer and silver, allowing selective removal of corrosion with “no apparent damage to the image itself” or “minimal removal of vital information” . Atmospheric pressure non‐equilibrium plasmas are a promising tool for the cleaning of open air surfaces like monuments walls or for selective treatment of surfaces …”

Recent progress in instrumental techniques for architectural heritage materials

“…The AFM is generally regarded as micro-destructive technique due to the fact that it was carried out on very small samples (a few mm 2 ). For instance, Pflugfelder et al [63] used AFM to investigate the gloss levels of alkyd resin layer in wall paintings before and after plasma treatment, and to obtain the optimal parameters of plasma cleaning. Taglieri et al [64] applied eco-compatible hydro-alcoholic nanoparticles (called nanolime) to repair Italian historic lime-based mortars, the AFM analysis showed the diameter and height of the nanoparticle were less than 50 and 5 nm, respectively.…”