Restoration in question and in practice. Module 4.

Why restore?

Some possible answers…

The restoration of built heritage is of crucial importance for the preservation of cultural and historical heritage. The main objective of this process is to maintain the architectural integrity of ancient buildings, thus contributing to the conservation of cultural identity and the transmission of knowledge to future generations.

The conservation of built heritage makes it possible to preserve authentic testimonies of the architectural history of a region or a society. By restoring historic buildings that have suffered damage, whether due to humidity, building movements, the effect of exposure to light, pollution (non-exhaustive list!)... we ensure that they remain visual documents of evolving architectural styles, building techniques and past ways of life.

Restoration also helps maintain the aesthetic value of historic buildings, revealing their original splendor. Reviving architectural details and repairing damage from wear, weather, or other factors preserves the inherent artistic beauty of these structures.

At the same time, the restoration of built heritage plays a crucial role in research and documentation. This process offers valuable information about construction techniques, materials used and the history of buildings, supporting the understanding of historic architecture.

By restoring built heritage, we ensure the transmission of cultural heritage. Historic buildings serve as tangible links between the past and present, reinforcing a sense of place and contributing to the cultural richness of a society.

Finally, the restoration of built heritage can also have economic implications, by preserving or increasing the value of historic real estate. This promotes sustainable use of existing resources while contributing to local economic development.

It is imperative that the restoration is carried out carefully, respecting strict ethical standards, in order to preserve the authenticity and integrity of the historic buildings as much as possible. Heritage restoration professionals follow specific protocols to ensure a careful and respectful approach to these architectural treasures.

Restoring an object, a work, means first of all doing everything possible so that they can be preserved in a “readable” way for future generations: it is “treating” them, repairing them, consolidating them, and thus restore to them a coherence that threatened to disappear. It’s giving them the opportunity to continue talking to us.

Restoration, what does it involve and who does it involve?

Restoration must certainly be conceived as a critical process, which involves in-depth reflection on the choices, methods and implications of the operations that will be carried out by the conservator-restorers and their teams.

Rating of dining options: Conservators must make deliberate choices about how to proceed with restoration: on the materials to use, the restoration techniques to apply and the level of intervention necessary. A critical approach involves careful evaluation of these choices, taking into account the impact on the authenticity, aesthetics and historical integrity of the object or building.

Analysis of historical and cultural contexts: The conservator-restorer takes into account the historical and cultural contexts in which the object, work or building exists. This means that it must recognize the evolution of the object over time, previous interventions and changes in cultural perception between the moment when it was designed and created, and the moment when we propose to carry out the operations of restoration. The objective is to ensure that the restoration respects the unique character of the object while meeting contemporary needs.

Awareness of ethical issues: As we can see, the restaurateur-conservator cannot apply a ready-made recipe. It must take into account the ethical issues linked to the preservation of heritage: this includes in particular sensitivity to various cultural perspectives, respect for the rights of communities linked to objects or buildings, and consideration of the social implications of restoration.

In-depth documentation: A critical approach requires detailed documentation of the entire restoration process. This includes collecting information about the original condition of the object or building, the restoration procedures carried out, and the reasons behind each decision. This documentation not only serves the preservation of knowledge, but also transparency and accountability. It is often based on scientific research work, with the help of specialized laboratories.

Engagement with stakeholders: Restoration must also be thought of as a social fact, which implies that those involved in restoration (the restaurateur and their teams of expert artisans) engage with stakeholders, including communities. local authorities, heritage experts, monument owners, etc. Open and transparent collaboration will contribute to more informed decision-making and a better understanding of the impact for the “users” of the restored structure.

Some key concepts

Illusionist restoration versus archaeological restoration : illusionist restoration, prior to other schools of restoration, seeks to visually recreate the original appearance of the object, building or work of art, while archaeological restoration focuses on preserving authenticity by minimizing interventions and respecting the traces of time. Choices between these approaches often depend on the specific nature of the object or building, cultural values, and long-term conservation objectives.

Currently, the aim of restoration tends first to preserve the work, then, possibly to restore its readability while retaining the material traces of its history.

There preventive conservation is to avoid or reduce potential damage to cultural objects, works of art, historical documents, heritage buildings and other elements of cultural heritage. Rather than focusing on direct interventions to restore damaged assets, preventive conservation focuses on proactively managing environmental factors, risks and conditions that could cause deterioration (for example, maintaining a dry climate on the premises frescoes, thus preventing humidity from damaging them) Preventive conservation measures and actions are indirect - they do not interfere with the materials and structures of the properties. They do not change their appearance.

Curative conservation – All actions directly undertaken on a cultural property or a group of properties with the objective of stopping an active process of deterioration or of strengthening them structurally. These actions are only implemented when the very existence of the assets is threatened, in the relatively short term, by their extreme fragility or the speed of their deterioration. These actions sometimes change the appearance of the goods.

Terminology of conservation-restoration of tangible cultural heritage, Resolution adopted by the members of ICOM-CC on the occasion of the XV Triennial Conference, New Delhi, September 22-26, 2008.

There derestoration is an approach which consists of going back in the restoration process by removing elements previously added or modified. In other words, it is an approach which aims to cancel or reverse certain previous restoration interventions. The idea behind derestoration is often linked to the desire to return to the original state of an object, building or work of art. This may involve removing layers of paint, removing modern architectural additions, or even restoring features that had been altered over time.

The key stages of a mural restoration project

1. The study: it involves evaluating the work to be restored in its spatial and architectural environment, the history of the place and the work, and their destination; to collect as much information as possible on historical, technical and aesthetic levels.

1.1 Surveys: useful for defining whether a decor is “hidden” under a covering (coating, canvas or paint) and in what condition it is.

We will proceed by delimiting squares of small surface area (or even on strips of small width, to delimit the length or height of the decoration) and by removing in these squares the covering obstructing the decoration, layer by layer, i.e. say in a way stratigraphic.

1.2 Statements:

graphics (per layer)
photographic, often with specific lighting (ultraviolet, infrared, etc.)
climatological (degree of humidity, temperature, etc.)
the composition of the support and the wall painting (several techniques exist, including laboratory microscopic analyzes of stratigraphic sections of samples taken from the work to be restored)
exposure and its consequences (south-facing walls drier and exposed to the sun's rays, etc.)

1.3 analyses:

salts and pH (with reagent strip on site; with cross-checking of more advanced techniques in the laboratory)
stratigraphic (on site with magnifying glasses, or in the laboratory)
spectro-chromatographic (in the laboratory, to identify the pigments that were used)

1.4 Identification of alterations:

Alterations can affect the support (carrying material; example: brick, stone), the substrate (intermediate layer; example: mortar or coating) or the pictorial layer. Salts, micro-organisms and lichens and algae are, along with cracks and other flaking due to the movement of building elements, the main alterations suffered by wall paintings.

1.5. Condition report and diagnosis:

Inventory of the work to be restored based on analysis and survey feedback. This is a decision support document which serves as a basis for establishing an initial diagnosis. It includes the conclusions concerning the causes of alteration (the most common remaining, in the field of wall paintings, humidity, pollution and degradation due to too long exposure to light) and the inventory and the degree of advancement of these alterations.

1.6. The intervention protocol including the condition report, the diagnosis, recommendations for treating alterations and an implementation methodology, is a working and communication document that the restorer-conservator provides to the stakeholders (including the supervisory authorities).

2. Clearance

Clearing is the act of removing the layers of coverings that cover a decor in order to restore its original appearance. Depending on the time of covering the decoration, the covering materials change: roughly speaking, it is lime and lime mortar until the 18th^th century, plaster and oil paint (18 and 19^th century), then glycerophthalic paint and latex paint (20^th century).

Mechanical release vs. chemical release: these are the two techniques used in restoration to remove alterations and non-original layers from wall paintings. Each of these methods has specific applications and is chosen based on the nature of the damage, the original materials, and the conservation objectives.

Mechanical Clearance: Mechanical removal refers to the use of physical tools to mechanically remove altered or unoriginal layers from a work of art. This may include the use of brushes, spatulas and scalpels

Applications:

Removing layers of dirt and dust: Soft brushes and mechanical tools are used to gently remove dirt accumulated over time without damaging the original surface.
Removal of covering paints or non-original varnishes: Where layers of old or non-original paint or varnish are present, mechanical release can be used to remove them without altering the underlying paint (scalpels).
Removal of thick surfaces: For lime mortar and related surfaces, mechanical clearance can allow precise removal; we will operate by picking (pick or chisel) or by resonance (fine hammer).

Precautions:

Avoid mechanical damage: The use of tools should be done carefully to avoid damage to the original layers.
Prior assessment: A careful assessment of the surface should be made before applying mechanical undercut to determine the most appropriate method.

Chemical Release: Chemical release involves using (most often with cotton) specific chemical substances to selectively dissolve or remove non-original or altered layers without damaging the original layers.

Applications:

Removal of non-original paint layers: Chemical solvents are often used to dissolve and remove layers of paint added later.
Removing old varnish: Old varnishes that may have yellowed or changed color over time can be chemically removed to reveal the original colors.
Treatment of chemical alterations: Certain types of alterations, such as salt efflorescence, can be chemically treated to remove them.

Precautions:

Proper selection of solvents: It is crucial to select appropriate solvents that will not react negatively with the original materials.
Preliminary tests: Before full surface application, preliminary tests are carried out on small areas to assess effectiveness and potential impact.

Salt treatment: knowledge of chemistry is necessary to tackle this operation. Depending on whether the salts are nitrates, carbonate and sulfate compounds or silicates, separate solvents, compresses or gels will be used.

For example, for nitrates which make surfaces powdery, we use Japanese paper in the form of compresses and distilled water. Once applied, the compresses dry and carry away the salts which have migrated from the surface of the paintings to the compress.

3. Consolidation:

Consolidation in the restoration of wall paintings is a crucial step aimed at strengthening areas where the painting is weakened, peeled off or showing alterations: it involves solidly linking the different layers and components of the work to be worked on (support/subjectile/pictorial layer)

The consolidation aims:

Stabilization of pictorial layers: Consolidation aims to restore the cohesion of the different layers of the wall paint, thus ensuring its structural stability.
Prevention of future detachments: By reinforcing weak areas, consolidation helps prevent future detachment or damage caused by environmental conditions or external factors.
Maintaining artistic integrity: The consolidation is carried out in such a way as to preserve the artistic integrity of the work, minimizing interventions while ensuring sufficient adhesion.

Consolidation Methods:

Consolidation Binder: The choice of binder depends on the specific characteristics of the wall paint and the materials used. Acrylic resins, thermoplastic glues or specific polymer-based glues can be used.
Specific Application: The binder is applied in a targeted manner to fragile areas using fine brushes, applications using a syringe or other suitable instruments. This application must be precise to avoid affecting intact parts of the work.
Controlled Pressure: In some cases, controlled pressure can be applied during or after application of the binder to promote adhesion and consolidation of the paint layers.

We will choose the consolidation product according to its qualities: elasticity, reversibility, resistance, penetration power, durability, etc.

For damaged mortars, we will dig the cracks and then fill the gaps with (most often) a mortar based on air lime and river sand. For spaces to be filled that are difficult to access, grouting will be carried out by injection (mixture of lime and filler – clay, very fine sand, marble powder, Spanish white, etc.)

For blisters (air pockets) caused by the separation of the various layers of coatings, mortars and paints, they will be filled by making a very small hollow with a drill and, after cleaning and moistening the area, by injecting a consolidator based on TAC or acryl 33 (lime acrylate)

To ensure consolidation, we may have to “put it in press”, that is to say subject the consolidated surface to controlled pressure (often using a wedged wooden board) in order to stabilize materials or promote adhesion of layers.

4. Cleaning:

Cleaning is a critical operation, because it is almost always irreversible. It is therefore a question of knowing “ how far not to go too far.”

Should we preserve the patina of time? Isn’t this an integral part of the life cycle of a work? Don't artists take this into account when they create their works?
So many questions that need to be asked Before to start the cleaning operation!

Information on the materials used to create the mural does not always allow us to know with certainty its composition, nor the reactions they will have with the products we will apply. It is therefore necessary to proceed in stages, first on samples with a very small surface area (rectangle less than 10 cm long), whether the cleaning is mechanical or chemical.

Mechanical cleaning: by scrubbing, application of soft or abrasive brushes, rubbing and scalpels.
Chemical cleaning: using solvents and detergents

5. Fixing the wall paint

Fixing the paint layer is an important step in the restoration of wall paintings. It aims to ensure the stability of pigments and pictorial layers, thus preventing their detachment or subsequent degradation. Fixing is often necessary when areas of the wall paint show signs of fragility, cracking or peeling.

Fixing products (fixatives) can be applied by spraying or spalting. This can be acrylic fixative, methylcellulose or resin.

6. Refilling

This involves equalizing the plane of the pictorial layer. Most often, lime mortars and plasters are used.

7. Pictorial reintegration

We saw it at the start of the course: archaeological restoration and illusionist restoration fall into two distinct schools, and the choice to apply one rather than the other depends on the decor to be restored. For a fresco that is too altered, there is no point in adopting the illusionist approach. We will then most often choose to create a colored background that is as neutral as possible in relation to the shades of what remains visible/readable of the fresco. If the gaps and gaps are not very important, then we can adopt the illusionist approach, and carry out a pictorial reintegration which will aim to reproduce the decor while distinguishing itself slightly from the original. The alterations must be reversible. Two techniques stand out here again: tratteggio, an arduous and time-consuming technique reserved for works of high value and visible up close, and the glazing technique (watercoloring with several passes allowing a play of transparencies) for other works ( the majority).

This presentation, necessarily summary, has no other aim than to allow you to approach the specialized literature with a basis for understanding the overall mural painting restoration projects. You will find examples and case studies on the site www.peintresdupatrimoine.com

do not hesitate do not contact us to inform you about the profession and the means to train!

artemisia

Scuola Edile -CPT Siena (ex ESSE), Italy

IFAPME/AWAP Train – AWAP Heritage (agencewallonnedupatrimoine.be)