Nanotechnologies in Cultural Heritage Conservation

Nanotechnologies in the Conservation of Cultural Heritage

• This book provides guidelines on using nanomaterials for the preservation of cultural heritage
• Written for practitioners, conservators, restorers, experts, museum staff, students, and scientists interested in artifact conservation

Key Aspects

• Nanomaterials provide practical solutions for various artistic substrates
• Improves traditional conservation by enhancing properties like compatibility and reduced toxicity

Physico-Chemical Compatibility

• Advanced systems minimize alterations to original physical and chemical properties of artistic/historical substrates

Toxicity

• Proposed nanomaterials are non-toxic or exhibit significantly reduced toxicity compared to traditional restoration materials like pure solvents

Restoration Intervention Control

• Advanced nanomaterials allow greater control, enabling highly controlled cleaning using micro-emulsions and chemical hydrogels

Feasibility and Reliability

• Innovative methodologies are feasible, reliable, and often simpler/faster than traditional methods, with gradual approaches granting long-term stability

Development of Advanced Systems

• Development derives from scientific knowledge, requiring fine knowledge of phase behaviors

Compendium Structure

• Overview of main nanomaterials developed: dispersions of nanoparticles, micellar solutions, microemulsions, and gels
• Features explanation and applicability
• Specific chapters dedicated to artistic/historical substrates i.e. wall paintings, stone, paper, canvas, and wood
• Considers main degradation processes
• Discusses practical applications and guidelines for cleaning, consolidation, or deacidification of artworks

Innovative Nanomaterials: Principles, Availability and Scopes

• Collaboration between scientists and conservators is fundamental for achieving reliable and durable results in the conservation of works of art
• Colloid and materials science provide tools for cleaning, consolidation, and pH control

Nanostructured materials

• Microemulsions, micellar solutions, dispersions of alkaline nanoparticles and chemical gels, can effectively counteract degradation without altering properties or causing drawbacks

Cultural Heritage Preservation

• Cultural Heritage is an invaluable patrimony that conveys artistic, historical, or anthropological values
• Its preservation is essential for intellectual progress, economic benefits, and addressing conservation issues

Effective Solutions

• Conservators and scientists seek solutions to counteract aging from light, temperature, humidity, microorganisms, chemical degradation, physical erosion, industrial pollution, vandalism, or handling

Compatible Materials

• Using compatible materials with same physico-chemical properties as treated artistic/historical substrates grants durability and minimizes drawbacks

Multidisciplinary Approach

• The cooperation between scientists, conservators, art historians is key for the restoration materials/techniques refinement

Role of Science

• Gathering information on the "anatomy" and "physiology" of the "patient" to address conservation issues
• Advanced diagnostic computational techniques are fundamental in determining the "disease" nature (degradation processes)

Colloids Science and Nanosciences

• Materials science, specifically colloids science and nanosciences, have improved effectiveness, reliability, and durability of restoration interventions

Aim of Chapter

• The goal is to introduce nanoparticles, nanostructured cleaning fluids and gels, highlighting principles, availability, and scopes

Overview

• The compilation provides practical information on the use of nanoparticles, fluids, and gels to tackle conservation issues/problematics

Nanoparticles

• Applying solid particles dispersion is preferred to solutions for reasons of solubility concerns of a consolidant in water
• Deacidifying agents like calcium hydroxide (Ca(OH)₂) nanoparticles can be deposited onto paper fibers to neutralize acidity
• The particles react with atmospheric CO₂ and it forms calcium carbonate (CaCO₃) which is not detrimental to aged cellulose

Nanostructured Materials

• They show at least one dimension of 10⁻⁹ m. There are bidimensional, monodimensional and zerodimensional

Material reactivity

• As particle size reduces, surface area increases, enhancing reactivity for reactions and transformations

Size Reduction Advantage

• Increased reactivity makes calcium hydroxide nanoparticles better deacidifying agents, favoring transformation into calcium carbonate

Dispersion Easing

• Reduction is important as it eases dispersion of solid particles into carrier solvents
• Dispersions enable easy brushing, spraying, or dripping onto surfaces, without needing stabilizers
• Short chain alcohols e.g. ethanol and propanol can be used and produce reasonably stable dispersions without surfactants

Penetration

• Reduced particle size favors penetration into wall paintings and wood surfaces
• Bookkeeper method with 1 µm magnesium oxide particles is discouraged for low porosity paper
• Magnesium hydroxide nanoparticles increase penetration and minimize haze
• Nanosized particles enhance organic-inorganic hybrid composites with improved mechanical properties, chemical resistance, and UV protection
• Polymer-silica nanoparticle films increase hydrophobicity.
• Klucel-TiO₂ nanocomposite protects paper from UV radiation and biofilms

Nanoparticles Synthesis and Preparation

• It's normally carried out at specialised facilities, but some products are presently for sale on the market

Nanostructured Cleaning Fluids

• This involves removal of undesired materials without damaging the original artifact

Damage Avoidance

• Intervention must be carried out in a controlled way

Variety of Materials to be Removed

• dirt, grime, soil, natural and synthetic coatings, adhesives, and varnishes

Hydrophobic Coatings

• Acrylic Vinyls and Vinyl-acetates. can strongly alter physico-chemical properties of carbonate based wall painting and stone resulting in medium or long-term damage

Multidisciplinary Approach in Conservation

• The extent of the removable layers that depends on factors such as historic, aesthetic ethics

Range of Cleaning Materials

• Soaps, alimentary products, inorganic materials , bile or saliva(contain surfactants)
• Branches of modern advanced chemistry and physical chemistry such as materials, colloid and nanosciences have carried out intense research on both theoretical and applicative aspects related to soft matter, such as binary or ternary systems composed of water, surfactants and other additives (e.g. solvents).

Microemulsions

• Organic solvent is dispersed into nano-sized surfactant micelles surrounded by a continuous water phase

Nanostructured Fluids vs. Organic Solvents

• Microemulsions are valid alternatives to the use of organic solvents, which involves a few drawbacks: action is limited, coatings and grimes are solved
• Contain surfactants • Processes that lead to the swelling (and/or solubilization) and removal of substances (polymers, wax, etc.) occur at the interface between nano-sized containers (micelles) • Nanostructured fluids can remove effectively harmful coatings that cant be dissolved by traditional solvents • Surrounding the removed hydrophobic material by surrounding it with hydrophilic phase- aqueous phase so it re-depositioned back in the matrix • Their low organic content reduces the health risk and environmental implications • They are also thermodynamically stable which means they can be used in different environments so in stable systems that consists of organic in water which result in macroscopically monophasic • Emulsifiers and micellar solutions are used for wall painting cleaning However by adding it can be used also by paper or canvas. Hydrogels allow the action controls

Gels

• This involves certain drawbacks related to safety risk so it has the capacity to alter.
• The ideal intervention should be fully selective chemical or physical. By enclosing something with a solvent is an ideal way to achieve it

Over the last few decades

Conservators have adopted different tools including modified natural products such as cellulose ethers. They use (e.g. Kucel®, Tylose), or synthetic polymers such as polyacrylic acids. These materials can be used to thicken solvents

• In the late 1980s Richard Wolbers developed “solvent gels”, this are obtained by dispersing polyacrylic acid in a solvent and them with weakly basic known as Ethomeen C12® and C25®. • Solvent gel still one of most used cleaning tools because of effective and versatility can also be used to control the action of detergents/enzymes/ .
• Like celluloses ethers and polyacrylic acids they are know as " physical gel"

Problem with "Physical gels"

• They leave slid residues on the surface but their effects have not be clarified. There long term residual of degradation like especially C25® can do potential damages in those areas.
• Research has focused in recent decade on the formulation of alterative system- they can and should be removed avoiding solid residue which is why polysaccharide - based been considering those include "gums"

Chemical Hydrogels

• They are recently finding more potential due to characteristics that gives advantages over some formulations
• semi-interpenetrating p(HEMA)/PVP networks where free chains of poly(vinylpyrrolidone)—PVP—are embedded into a network formed by poly(2-hydroxyethyl methacrylate)—p(HEMA). These systems exhibit the mechanical. In both p(HEMA)/PVP ratio and water use during preparation affects all gel.

Consolidation of Wall Paintings and Stone

• This chapter focuses on using nanoparticles dispersions for consolidation of immovable artworks like wall paintings and stone
• It will look at the advantages and practicalities of this methodology.
• The structure, main composition, and properties of wall paintings/stone from historical/artistic heritage are briefly mentioned
• Typically a wall painting consists of three different superimposed layer which is similar to (SEE FIG 2.1)
• The most inner layer-arriccio, 3:1 (v/v) mixture of coarse sand and lime paste (Ca(OH)2 and water).

arriccio

• Italian word that means curl. To improve adhesion for the second layer is called Intonaco
• The intonaco is made using 2:1 or 1:1 (v/v) mixes with finer sand particles and lime
• To obtain a smooth area the outside layer with pigments is 50 to 500um to paint with
• in fresco" is the that pigment is is in Lime and apply on wet or wet Intonaco.
• a secco (in dry conditions).The binder ofpigments is not CaCO3, but a material of either vegetal.
• Some use Gum,exctract or oil as animal (cassen, ect.)
• The corrosion of calcium carbonate and the mechanical stress due to salts crys tallization jeopardize the surface of wall paintings, which can exhibit efflorescence or flaking layers (look in example in fig 2.2)

Protective Coating

• Starting in 1960s, with synthetic products such, silicate, vinyl, epoxy
• High Power give fast easy for The the and readmission of flaking