Advanced Coatings for Cultural Heritage Preservation

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (15 December 2020) | Viewed by 35175

Special Issue Editors


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Guest Editor
Institute of Geosciences and Earth Resources, National Research Council, Via G. La Pira 4, 50121 Florence, Italy
Interests: polymeric materials; surface coating; hydrophobicity and superhydrophobicity; self-cleaning properties; cultural heritage protection and restoration
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Guest Editor
Department of Chemistry “Ugo Schiff”, University of Florence, Florence, Italy
Interests: conservation of the cultural heritage; wood and paper consolidants; wood and stone protective agents; adhesives; biopolymers; biorefinery processes; homogenous catalysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The protection of cultural assets against natural and anthropic causes has been sought since ancient times. The application of natural or synthetic coating agents is considered to be the best sustainable solution to mitigate the degradation phenomena induced by various factors. The superficial performance and interfacial performance of protective agents for cultural heritage impose particular requirements that must be met. The chemical and physical characteristics of materials, as well as their resistance to degradation agents (including micro-biological attack), limit the choice of coating agents. Particular attention has recently been paid to materials by which a specific type of performance can be obtained, such as superamphiphobicity, self-cleaning, photo-stability, and anti-biofouling.

The aim of this Special Issue of Coatings on "Advanced coatings for cultural heritage preservation" is to present recent advances in the field through original research papers and critical review articles.

Topics of interest include, but are not limited to:

  • New coatings for stone protection and outdoor artifacts;
  • Polymeric materials for fine arts and indoor items conservation;
  • Coating efficacy evaluation;
  • Coating durability and modeling
Dr. Mara Camaiti
Prof. Dr. Antonella Salvini
Guest Editors

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Published Papers (10 papers)

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Research

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18 pages, 75653 KiB  
Article
Design of Novel Photocatalytic Films for the Protection of Architectural Surfaces via the Incorporation of Green Photocatalysts
by Dimitrios Stefanakis, Themis Krasoudaki, Anastasios-Ioannis Kaditis, Asterios Bakolas and Pagona-Noni Maravelaki
Coatings 2021, 11(8), 934; https://doi.org/10.3390/coatings11080934 - 4 Aug 2021
Cited by 3 | Viewed by 2446
Abstract
In conservation science the demand of multifunctional green materials displaying water repellency, consolidation, resistance to organic pollutants and pigments is constantly increasing. This research developed a green nanocomposite exhibiting photocatalytic, hydrophobic, consolidation and self-cleaning properties. This was achieved by synthesizing a TiO2 [...] Read more.
In conservation science the demand of multifunctional green materials displaying water repellency, consolidation, resistance to organic pollutants and pigments is constantly increasing. This research developed a green nanocomposite exhibiting photocatalytic, hydrophobic, consolidation and self-cleaning properties. This was achieved by synthesizing a TiO2 photocatalyst enriched with carbon dots (C-dots) and successfully incorporated into a tetraethoxysilane nanocomposite modified with nano-calcium oxalate and polydimethylsiloxane. The TiO2/C-dots that were prepared with a simple, low temperature, cost-effective and large-scale procedure were assessed via analytical and spectroscopic techniques and were resulted in anatase structure ranging in size from 10 to 40 nm. Photooxidation measurements displayed that TiO2/C-dots nanoparticles could photodegrade completely Methyl Orange (MO) under UV and visible irradiation after 120 min. The photocatalytic performance of the nanocomposite with TiO2/C-dots resulted promising under UV after longer irradiation time. The degradation of MO was faster on bulk xerogels containing the TiO2/C-dots than the corresponding ones with TiO2. The treatment of concrete, limestone and lime mortars with the nanocomposite proved to be compatible with the substrates in terms of aesthetical aspects. This study demonstrates encouraging potential for large-scale production of a multifunctional protective composite that offers hydrophobicity, self-cleaning properties and consolidation to architectural surfaces. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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21 pages, 32289 KiB  
Article
High Efficiency Fluorinated Oligo(ethylenesuccinamide) Coating for Stone
by Mara Camaiti, Villiam Bortolotti, Yijian Cao, Alessandra Papacchini, Antonella Salvini and Leonardo Brizi
Coatings 2021, 11(4), 452; https://doi.org/10.3390/coatings11040452 - 14 Apr 2021
Cited by 3 | Viewed by 2801
Abstract
The protection of stone cultural assets is related to the transformation of the surface characteristic from hydrophilic to hydrophobic/superhydrophobic through the application of a coating. The suitability of a coating depends not only on its capability to dramatically change the surface wettability, but [...] Read more.
The protection of stone cultural assets is related to the transformation of the surface characteristic from hydrophilic to hydrophobic/superhydrophobic through the application of a coating. The suitability of a coating depends not only on its capability to dramatically change the surface wettability, but also on other parameters such as the modification of kinetics of water absorption, the permanence of vapor diffusivity, the resistance of the coating to aging and the low volatile organic compound emissions during its application. In this work, an oligo(ethylensuccinamide) containing low molecular pendant perfluoropolyether segments (SC2-PFPE) and soluble in environmentally friendly solvents was tested as a protective agent for historic stone artifacts. Magnetic resonance imaging and relaxometry were employed to evaluate the effects of the surface wettability change, to follow the water diffusion inside the rock and to study the porous structure evolution after the application of SC2-PFPE. A sun-like irradiation test was used to investigate the photo-stability of the product. The results demonstrate that the highly photo-stable SC2-PFPE minimizes the surface wettability of the stone by modifying the water sorptivity without significantly affecting its porous structure and vapor diffusivity. The improved performance of SC2-PFPE in comparison to other traditional coatings makes it a potential candidate as an advanced coating for stone cultural heritage protection. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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18 pages, 33167 KiB  
Article
Improving the Protective Properties of Shellac-Based Varnishes by Functionalized Nanoparticles
by Maduka L. Weththimuni, Chiara Milanese, Maurizio Licchelli and Marco Malagodi
Coatings 2021, 11(4), 419; https://doi.org/10.3390/coatings11040419 - 4 Apr 2021
Cited by 21 | Viewed by 4354
Abstract
Shellac is a natural varnish still known as one of the most elegant finishes for furniture and musical instruments, and currently used for restoration and refinishing of wooden antiques. However, it displays some limitations such as (i) sensitivity to alcoholic solvents (ii) softness [...] Read more.
Shellac is a natural varnish still known as one of the most elegant finishes for furniture and musical instruments, and currently used for restoration and refinishing of wooden antiques. However, it displays some limitations such as (i) sensitivity to alcoholic solvents (ii) softness of the coating, and (iii) considerable weathering due to photo- and bio-degradation. Hence, the main aim of this study was to improve the properties of shellac-based finish by introducing functionalized nanoparticles. Two inorganic nano-sized materials were considered: ZnO that was expected to reduce photo- and bio-degradation problems, and ZrO2 that was expected to improve the hardness of the varnish. Nanoparticles were synthesized and treated with a bifunctional silane coupling agent. Both plain and functionalized nanoparticles were extensively characterized using different experimental techniques. Functionalized nanoparticles were grafted on shellac through a reaction involving the epoxy-rings introduced on their surface. The resulting modified varnishes were applied on maple wood specimens according to traditional procedures. Different instrumental techniques and testing methods were used to characterize both nano-sized materials and the corresponding nanocomposites, as well as to evaluate the performance of the new coatings. The investigated composite materials display the same aesthetic appearance as plain shellac, while some other properties were improved. In particular, both nanocomposites are distinctly less soluble in alcohols than plain shellac and display antifungal properties. Moreover, coating containing functionalized ZnO nanoparticles displays photo-protection behavior, while shellac modified with ZrO2 nanoparticles exhibits a higher hardness when compared to the traditional varnish. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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12 pages, 3960 KiB  
Article
TEOS-Based Superhydrophobic Coating for the Protection of Stone-Built Cultural Heritage
by Fotios G. Adamopoulos, Evangelia C. Vouvoudi, Eleni Pavlidou, Dimitris S. Achilias and Ioannis Karapanagiotis
Coatings 2021, 11(2), 135; https://doi.org/10.3390/coatings11020135 - 27 Jan 2021
Cited by 34 | Viewed by 5698
Abstract
Tetraethyl orthosilicate (TEOS) is extensively used in the conservation of stone-built cultural heritage, which is often subjected to water-induced degradation processes. The goal of this study was to produce and study a TEOS-based material with the ability to repel liquid water. A sol [...] Read more.
Tetraethyl orthosilicate (TEOS) is extensively used in the conservation of stone-built cultural heritage, which is often subjected to water-induced degradation processes. The goal of this study was to produce and study a TEOS-based material with the ability to repel liquid water. A sol solution of TEOS and 1H,1H,2H,2H-perfluorooctyl triethoxysilane (FAS) was prepared and deposited on marble. The static contact angles (CAs) of water drops on the coated marble surface were >170° and the sliding angles (SA) were <5°, suggesting that superhydrophobicity and water repellency were achieved on the surface of the synthesized TEOS-based coating. FTIR and SEM-EDS were employed to characterize the produced coating. The latter offered good protection against water penetration by capillarity, reducing the breathability of marble only by a small extent and with practically no effect on its aesthetic appearance. The durability of the coating was evaluated through various tests that provided very promising results. Finally, the versatility of the method was demonstrated as the TEOS-based coating was successfully deposited onto glass, brass, wood, silicon, paper and silk, which obtained extreme wetting properties. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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12 pages, 1506 KiB  
Article
Enhanced Historical Limestone Protection by New Organic/Inorganic Additive-Modified Resins
by Eleonora Pargoletti, Valeria Comite, Paola Fermo, Valentina Sabatini and Giuseppe Cappelletti
Coatings 2021, 11(1), 73; https://doi.org/10.3390/coatings11010073 - 10 Jan 2021
Cited by 9 | Viewed by 2584
Abstract
The Cultural Heritage deterioration is a spontaneous decay process due to water percolation and air pollutant deposition. In this context, novel acrylic (Twinswet, TW) and siloxane-based (Alpha®SI30) resins were exploited starting from commercial products and then modified by adding either a [...] Read more.
The Cultural Heritage deterioration is a spontaneous decay process due to water percolation and air pollutant deposition. In this context, novel acrylic (Twinswet, TW) and siloxane-based (Alpha®SI30) resins were exploited starting from commercial products and then modified by adding either a commercial polysiloxane-based additive (TegoPhobe 1500N) or a precursor of SiO2 nanoparticles (Tetraethyl ortosilicate, TEOS) to improve the Vicenza stone surface hydrophobicity. Properties of the coated materials were studied using different techniques such as water contact angle (WCA), capillary absorption, colorimetric and water vapor permeability measurements. Accelerated UV aging and eight-month outdoor exposure tests (at Milan University campus) were also performed to determine the coatings durability. Notably, the addition of both additives slightly enhanced the surface hydrophobicity resulting in WCAs of about 140°, and decreased the water absorption especially for Alpha-based resins. Conversely, a reduction of water vapor permeability was observed, even if within the threshold value of 50%. Concerning the color variation, Alpha®SI30 preserved the stone external aspect; instead, TW smoothly modified the surface color. All of the studied coatings were stable to both UV aging and outdoor exposure. Hence, the present modified commercial coatings revealed to be very promising for the protection of historical monuments. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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8 pages, 2527 KiB  
Article
Preliminary Study of the Targeted Cleaning of an Artificial Gypsum Layer on White Marble
by Yan Liu, Taoling Dong, Kun Zhang, Fuwei Yang and Liqin Wang
Coatings 2021, 11(1), 37; https://doi.org/10.3390/coatings11010037 - 1 Jan 2021
Cited by 4 | Viewed by 2400
Abstract
Targeting cleaning of the artificial gypsum layer on white marble was studied. It was conducted by means of the specific depletion of the calcium and sulfate ions by the barium carbonate scavenger, which led to the continuous dissolution and clearance of gypsum layer. [...] Read more.
Targeting cleaning of the artificial gypsum layer on white marble was studied. It was conducted by means of the specific depletion of the calcium and sulfate ions by the barium carbonate scavenger, which led to the continuous dissolution and clearance of gypsum layer. The cleaning effect was evaluated by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), X-ray diffraction (XRD), capillary suction, and color difference measurement. By this method, only the gypsum layer was cleared away and the carbonate substrate of marble was left intact at the same time. This method will be highly useful for the conservation of marble relics from surface weathering. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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12 pages, 3258 KiB  
Article
Modified Graphene-FEVE Composite Coatings: Application in the Repair of Ancient Architectural Color Paintings
by Peng Fu, Ge-Le Teri, Xiao-Lian Chao, Jing Li, Yu-Hu Li and Hong Yang
Coatings 2020, 10(12), 1162; https://doi.org/10.3390/coatings10121162 - 28 Nov 2020
Cited by 13 | Viewed by 3030
Abstract
In recent years, based on the urgent need in the field of cultural heritage conservation, the research and development of coatings have attracted much attention. FEVE (trifluorovinyl chloride and vinyl ether copolymer) is one of the reinforcing materials in the protective coatings of [...] Read more.
In recent years, based on the urgent need in the field of cultural heritage conservation, the research and development of coatings have attracted much attention. FEVE (trifluorovinyl chloride and vinyl ether copolymer) is one of the reinforcing materials in the protective coatings of color paint. However, it has problems such as compactness, low tensile strength, and poor resistance to aging. Therefore, modified graphene was introduced and combined with FEVE coatings (FEVE/m-GO) to optimize their adhesion, compactness, resistance to corrosion, and performance at shielding the paintings from ultraviolet light. The structural features of the hybrid films were characterized by UV–Vis spectroscopy, transmission electron microscopy, infrared spectroscopy, etc. In addition, the water absorption, mechanical properties, color difference test, and aging resistance of the FEVE/m-GO and simulated samples were investigated. The results showed that the hybrid film with 0.04% m-GO incorporation as an effective consolidant exhibited outstanding comprehensive performance. This composite material was used in the protection and consolidation of the Sanyou Xuan ancient architectural color painting in the Palace Museum, which opened up a new way of thinking about the long-term conservation of color paintings. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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15 pages, 3260 KiB  
Article
Artificial Ageing of Photocatalytic Nanocomposites for the Protection of Natural Stones
by Marco Roveri, Sara Goidanich and Lucia Toniolo
Coatings 2020, 10(8), 729; https://doi.org/10.3390/coatings10080729 - 24 Jul 2020
Cited by 8 | Viewed by 2501
Abstract
During the last ten years, photocatalytic nanocomposites combining titania nanoparticles with silicon-based matrices have received increasing attention in the stone conservation research field, because they offer an effective multifunctional approach to the issue of stone protection. However, much work still has to be [...] Read more.
During the last ten years, photocatalytic nanocomposites combining titania nanoparticles with silicon-based matrices have received increasing attention in the stone conservation research field, because they offer an effective multifunctional approach to the issue of stone protection. However, much work still has to be done in studying the behaviour of these nanocomposites in real environmental conditions and understanding to what extent they are able to retain their effectiveness and compatibility once applied on outdoor surfaces. The latter is a key information that should lie at the basis of any successful conservation and maintenance campaign. The present study provides insight into this relevant topic trough laboratory testing by assessing the artificial ageing of two silane-based photocatalytic nanocomposites, previously selected through an accurate testing on different natural stones. Three accelerated ageing procedures, based on artificial solar irradiation, heating and rain wash-out, allowed simulating about two years of outdoor exposure to some of the weathering factors to which stones are normally subjected. The results provided quite accurate information about the long-term behaviour of the products and on the role that the stone properties play therein. It was shown that, when the products are able to penetrate deeply enough inside the stone pores, they retain much of their hydrophobising and photocatalytic properties and maintain a good compatibility with the stone substrates, even after partial chemical degradation of the alkyl-silica matrices has occurred on the very stone surface. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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Review

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16 pages, 2150 KiB  
Review
Testing New Coatings for Outdoor Bronze Monuments: A Methodological Overview
by Paola Letardi
Coatings 2021, 11(2), 131; https://doi.org/10.3390/coatings11020131 - 26 Jan 2021
Cited by 23 | Viewed by 3880
Abstract
Coatings to be used for cultural heritage protection face peculiar challenges. In the last few decades, several projects addressed the issue of new treatments in the field of copper alloy artworks. Nonetheless, no one has yet been recognised as a more acceptable solution [...] Read more.
Coatings to be used for cultural heritage protection face peculiar challenges. In the last few decades, several projects addressed the issue of new treatments in the field of copper alloy artworks. Nonetheless, no one has yet been recognised as a more acceptable solution with respect to traditional choices, with their known limits. The lack of standard methods to test new coatings that can be effectively applied to artworks make it more difficult to compare different studies and open the way to practical use in restoration. Over the years, several issues have gradually been better focused, even though they are not yet widely considered in new coatings efficacy evaluation for application on copper alloy artifacts. They are mainly linked to the quite complex surface of this category of heritage objects and the role it plays on coating effectiveness. An overview of the variety of relevant surface properties is provided (presence of corrosion products and old protective treatments, cleaning methods, surface unevenness, just to name a few) with a special focus on the role of coating performance. Some methodological choices are discussed for the selection of mock-ups, testing techniques and weathering procedures, with peculiar attention to comparison with real artworks. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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23 pages, 3854 KiB  
Review
Current Status and Future Prospects of Applying Bioinspired Superhydrophobic Materials for Conservation of Stone Artworks
by Yijian Cao, Antonella Salvini and Mara Camaiti
Coatings 2020, 10(4), 353; https://doi.org/10.3390/coatings10040353 - 4 Apr 2020
Cited by 20 | Viewed by 3999
Abstract
The development of innovative materials is one of the most important focus areas in heritage conservation research. Eligible materials can not only protect the physical and chemical integrity of artworks but also preserve their artistic and aesthetic features. Recently, as one of the [...] Read more.
The development of innovative materials is one of the most important focus areas in heritage conservation research. Eligible materials can not only protect the physical and chemical integrity of artworks but also preserve their artistic and aesthetic features. Recently, as one of the hot research topics in materials science, biomimetic superhydrophobic materials have gradually attracted the attention of conservation scientists due to their unique properties. In fact, ultra-repellent materials are particularly suitable for hydrophobization treatments on outdoor artworks. Owing to their excellent hydrophobicity, superhydrophobic materials can effectively prevent the absorption and penetration of liquid water as well as the condensation of water vapor, thus greatly relieving water-induced decay phenomena. Moreover, in the presence of liquid water, the superhydrophobic surfaces equipped with a self-cleaning property can clean the dirt and dust deposited spontaneously, thereby restoring the artistic features simultaneously. In the present paper, besides the basic principles of wetting on solid surfaces, materials, and methods reported for preparing bioinspired ultra-repellent materials, the recently proposed materials for art conservation are also introduced and critically reviewed, along with a discussion on the droplet impact and durability of the artificial superhydrophobic surfaces. Lastly, the current status and the problems encountered in practical application are also pointed out, and the focus of future research is presented as well. Full article
(This article belongs to the Special Issue Advanced Coatings for Cultural Heritage Preservation)
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