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The conservation and restoration of waterlogged wood is the process undertaken by conservator-restorers of caring for and maintaining waterlogged wooden artefacts to preserve their form, and the information they contain. It covers the processes that can be taken by conservators, archaeologists, and other museum professionals to conserve waterlogged wood. This practice includes understanding the composition and agents of deterioration of waterlogged wood, as well as the preventive conservation and interventive conservation measures that can be taken.
Waterlogged wood is a wooden object that has been submerged or partially submerged in water and has affected the original intended purpose or look of the object. Waterlogged wood objects can also include wood found within moist soil from archaeological sites, underwater archaeology, maritime debris, or damaged wood objects. Conservation of waterlogged wood has changed throughout time. Due to the delicate structure of this organic material, conservators and museum professionals alike have struggled with finding a textbook method. An example of the conservation of wood and how it has changed over time can be illustrated by the conservation treatments of a Kefermarkt altar. The earliest attempt at wood conservation is recorded as late as 1852–1855, A. Stifter treated the Kefermarkt altar in Austria with table salt in an attempt to protect the wood against pests. In around 1916-1918 Councillor Bolle attempted to protect the wood altar from pests included brushing the wood with petroleum and hexachloroethane. Finally, in 1929 the use of hydrogen cyanide relieved the pest problem and preserve the woods longevity. [1] From a conservation standpoint, waterlogged or not, wood has been difficult to preserve because it is an organic material.
Wood is an organic material and decays under biological and chemical degradation when buried or submerged above water or soil. Wood, an organic material produced by plants, are chemically composed of: carbohydrates (cellulose and hemicellulose), lignin and other components (aliphatic acids, alcohols, proteins and inorganic substances) in a smaller amount. The most important composition of the plant is the cellulose. The cellulose accounts for the majority of the cell, about 40% to 50% of the wood's total mass. Hemicellulose represents the second most important carbohydrate and accounts for 20% to 30% of the wood's cell. [3] In cases of extreme wetness or dryness, wood can be preserved until the extreme environment is disrupted. Conservation of wooden waterlogged objects is dependent on the natural wood type and biological structure. Wood is separated into two categories, hardwoods and softwoods. The category the waterlogged wood falls into can determine the amount of porous absorption. Hardwoods are classified as angiosperms. Angiosperms are considered porous woods because of the vessel pores. Softwoods are gymnosperms and are considered non-porous because of the lack of vessel pores. The type of wood and the availability of vessel pores largely affect how conservators treat and preserve waterlogged wood. [4] Waterlogged wood objects can be found in a range of excavations sites. For example, waterlogged wood is something an archaeologist might stumble upon during an excavation either from the wood being submerged or near water or being in moist soil over time. Wood especially survives in archaeological sites that are dark anaerobic environments where bacteria that would cause wood decay cannot live. [5]
There are several agents of deterioration that affect waterlogged wood, mostly due to its environment. The major threats to deterioration include physical forces, pests, incorrect temperature, incorrect relative humidity, and custodial neglect. Attempts at preventive conservation focus on creating a stable storage environment, documentation, and resources to provide the environmental settings that keep an object as stable as possible. The excavation of waterlogged wood removes it from its anaerobic environment, exposing the wood to oxygen which continues the wood's deterioration. An environment with incorrect relative humidity and temperature can encourage bacteria and fungi growth, which adds to the decay and can attract pests. While interventive conservation treatments must balance "remov[ing] the waterlogging water (not the 'bound' water which is part of the wood structure itself) without causing shrinkage or cell wall collapse," [6] preventive conservation tactics include keeping the waterlogged wood in its original state (in water or a solution), with routine maintenance, or reburial of the wood to recreate the anaerobic environment it was once preserved within.
Inconsistent relative humidity and temperature provide the perfect environment for mold and fungi growth on waterlogged wood. Growth of mold or other bacteria requires immediate attention to control damage. Natural cellulosic materials are the best environment for mold spores to grow and mature. "Mold is a microorganism that produces enzymes that convert the cellulose in fibers to soluble sugar that is metabolized as food. Proteins are generally less susceptible, but keratinophilic fungi will feed on, and damage, these fibers as well". [7] Similar to wood found in nature, mold and other feeding organisms are attracted to the material, this includes pests and naturally occurring fungi and bacteria. Mold is a high risk for waterlogged wood even with controlled relative humidity and temperature due to the resilient nature of the organisms and the perfect environment waterlogged wood provides as a food source to the growth of spores.
Within maritime environments one of the largest pest threats to waterlogged wood includes shipworms (Teredinidae). Shipworms bore into wood that is immersed in seawater.[ citation needed ] Within a museum exhibit or storage environment and post treatment of waterlogged wood objects, there are a number of wood-boring pests that feast on wood. Two of which include the wood-boring/powderpost beetle and termites. Wood-boring beetles can include several different types within the board category. Each type of beetle could target a different type of wood. Evidence of pest deterioration includes powder-like frass near entry and exit holes within the wood. Termites also feast on and live below the surface of the wood so they can be more difficult to detect. Termites discharge six-sided fecal pellets and, if found on a wooden object, could be used to determine the type of pest damage [8]
Physical deterioration of waterlogged wood can happen immediately through the evaporation of the water. If this happens rapidly, the cells in the wood can shrink and collapse. This damage might be inevitable depending on accessibility to treatment. Additionally waterlogged wood should never be handled extensively or put on exhibit for long periods of time. Most waterlogged wood is such that decayed wood cells in the material fill with water. Depending on the wood type and how long the wood has been in water, removal of the water from the cells too rapidly (in the form of natural drying or other) could apply major stress to the cell walls and cause them to collapse. Improperly dried waterlogged irreversibly shrinks, warps, cracks and there is risk of loss to the original surface. [5]
Waterlogged wood should be in the environment that it is found in (and kept wet) until a stable treatment proposal in conversation with a professional conservator is decided. To limit mold growth, waterlogged wood should be stored with proper relative humidity and temperature that does not encourage mold. [9] Waterlogged wood will retain its structure as long as it is wet.
The treatment of waterlogged wood should be undertaken by a professional conservator who understands how materials degrade and how the introduction of new materials might affect or at worst accelerate the degradation process. One of the largest issues with treatment on waterlogged wood is finding a way to remove the water in the wood but keep the water that is part of the material. Preventing cell wall collapse (which causes shrinking, cracking, and further damage) of the waterlogged wood while drying is the largest struggle and main goal of treatment. Some commonly-used treatments include the Polyethylene Glycol (PEG) method, Sucrose method, Acetone-Rosin method, alcohol-Ether method, Camphor-Alcohol method, freeze drying, and silicone oil treatment, or various combinations.
The purpose of the polyethylene glycol is to remove water from the wood while simultaneously bulking the deteriorated wood cells. PEG is applied to the surface, either by spraying or immersing the object in a solution of PEG in water. Over the course of the treatment, PEG is slowly increased in concentration, pushing out the excess water, coating the interior walls of the wood cells with PEG, which, depending on the molecular weight selected, will provide support once the artifact is dried. PEG compounds with different molecular weights may be used depending on the wood type, level of deterioration, and scope of project. [5]
The PEG treatment is often paired with vacuum freeze-drying, as the eutectic point of most PEG solutions is below the freezing point of water. This allows the "free" waterlogging water to sublimate in the process of freeze-drying, which minimizes damage to the wood by preventing ice from forming within the cells and expanding, causing more shrinking and warping. [5] Some artifacts are too large to fit in a commercially available freeze-drier (see the treatment for Vasa or Mary Rose [10] or the Bremen cog [11] ).
Identical to PEG treatment process but sucrose is used instead of PEG solution. The cells of the wood are replaced by sucrose, rather than water. Originally recommended as a low-cost method for treating waterlogged wood, sucrose treatments are inconsistent in how much shrinkage they prevent, especially for severely degraded wood. [12]
Acetone-Rosin Treatment is sometimes used on dense wood that cannot be penetrated by PEG. [13] This would include softwoods that are nonporous. The goal of this treatment is to replace cells of wood with natural rosin. Rosin is a natural resin that is produced within some woods, for example pines naturally produce resin and are considered a softwood. As a volatile solvent treatment option, the impact on the health and safety on the workplace must be considered.
This treatment follows the similar treatment of the PEG solution but instead of replacing the cells with another solution, the cells are replaced with alcohol and when the alcohol evaporates the cell and overall object is dehydrated. As a volatile solvent treatment option, the impact on the health and safety on the workplace must be considered.
Camphor treatment is similar to the Alcohol-Ether treatment but instead of a quick evaporation of the alcohol inside of the cells, the camphor alcohol slowly replaces cell walls with camphor which goes from a solid to a gas state over time, keeping walls of cells bulked. As a volatile solvent treatment option, the impact on the health and safety on the workplace must be considered.
Treatment must also take into account the type of water the wood was found in. Waterlogged wood recovered from marine environments may contain high levels of salts, which must be removed from the waterlogged wood to prevent further damage on drying. This can be done by a desalination process. Desalination is often completed in bath changes using clean water. Sometimes disinfectants (fungicides or algaecides) are added to prevent the development of damaging organisms. However, the most commonly used and recommended because of its lesser toxicity is a mixture of boric acid and borax. The desalination process takes a long period of time and is necessary that the water is changed until the concentration of excreted of soluble salts reach its maximum. [14]
In January 2016, a mid-18th century ship was discovered on the waterfront of Alexandria, Virginia. Conservation efforts include keeping the wood submerged and wet since the wooden frame was waterlogged. The conservation of this ship is ongoing. When the waterlogged wooden frame was originally removed from the archaeological site, the timber frames were stored in fresh water vats until June 2017. The framed structure was then packaged and sent to the Conservation Research Laboratory at Texas A&M University for conservation. Documentation and conservation included laser scanning, modeling, X-ray, and wood degradation analysis before the treatment using polyethylene glycol and vacuum freeze drying [15]
After finding the vessel Mary Rose objects and what was left of the ship were placed in a passive storage which slowed down the process of immediate deterioration removing the vessel from its extreme environment. In 1994, an elaborate three phased conservation treatment began on Mary Rose. From 1993 to 2003 was the first phase that consisted of the wood getting sprayed with low-molecular-weight PEG to replace the water in the cellular structure of the wood. The second phase from 2003 to 2010, raised the molecular-weight of the PEG solution with the purpose to strengthen the outer surface layers. The third phase in 2016, included controlled air drying. [16] [17]
The Vasa is a Swedish 1628 ship found archaeologically and was very well preserved. Completely submerged for 333 years allowed for the wood to be completely waterlogged but pollution in the 20th century off of the city Stockholm was able to kill any microorganisms that would have feast on the wreck, like the shipworm. Vasa was sprayed with a PEG solution for 17 years followed by a period of drying which is ongoing. [18]
National Park Service Waterlogged/Water damage wood Conserve O Gram [19]
Conserving Waterlogged Wood - Maryland Archaeological Conservation Laboratory
Conservation and restoration of immovable cultural property describes the process through which the material, historical, and design integrity of any immovable cultural property are prolonged through carefully planned interventions. The individual engaged in this pursuit is known as an architectural conservator-restorer. Decisions of when and how to engage in an intervention are critical to the ultimate conservation-restoration of cultural heritage. Ultimately, the decision is value based: a combination of artistic, contextual, and informational values is normally considered. In some cases, a decision to not intervene may be the most appropriate choice.
With respect to cultural property, conservation science is the interdisciplinary study of the conservation of art, architecture, technical art history and other cultural works through the use of scientific inquiry. General areas of research include the technology and structure of artistic and historic works. In other words, the materials and techniques from which cultural, artistic and historic objects are made.
The conservation and restoration of parchment constitutes the care and treatment of parchment materials which have cultural and historical significance. Typically undertaken by professional book and document conservators, this process can include preventive measures which protect against future deterioration as well as specific treatments to alleviate changes already caused by agents of deterioration.
Conservation and restoration of movable cultural property is a term used to denote the conservation of movable cultural property items in libraries, archives, museums and private collections. Conservation encompasses all the actions taken toward the long-term preservation of cultural heritage. Activities include examination, documentation, treatment, and preventive care, which is supported by research and education. Object conservation is specifically the actions taken to preserve and restore cultural objects. The objects span a wide range of materials from a variety of cultures, time periods, and functions. Object conservation can be applied to both art objects and artifacts. Conservation practice aims to prevent damage from occurring, a process known as 'preventive conservation'. The purpose of preventive conservation is to maintain, and where possible enhance, the condition of an object, as well as managing deterioration risks, such as handling and environmental conditions. Historically, object conservation was focused on the category of fine arts but now many different types of objects are conserved. Each type of object material, typically denoted by organic or inorganic then the specific medium, requires a specialized professional conservator and often requires collaborative work between museum staff, scientists, and conservators.
Collection maintenance is an area of collections management that consists of the day-to-day hands on care of collections and cultural heritage. The primary goal of collections maintenance or preventive conservation is to prevent further decay of cultural heritage by ensuring proper storage and upkeep including performing regular housekeeping of the spaces and objects and monitoring and controlling storage and gallery environments. Collections maintenance is part of the risk management field of collections management. The professionals most involved with collections maintenance include collection managers, registrars, and archivists, depending on the size and scope of the institution. Collections maintenance takes place in two primary areas of the museum: storage areas and display areas.
The conservation and restoration of books, manuscripts, documents, and ephemera is an activity dedicated to extending the life of items of historical and personal value made primarily from paper, parchment, and leather. When applied to cultural heritage, conservation activities are generally undertaken by a conservator. The primary goal of conservation is to extend the lifespan of the object as well as maintaining its integrity by keeping all additions reversible. Conservation of books and paper involves techniques of bookbinding, restoration, paper chemistry, and other material technologies including preservation and archival techniques.
An Objects conservator is a professional, working in a museum setting or private practice, that specializes in the conservation of three-dimensional works. They undergo specialized education, training, and experience that allows them to formulate and implement preventive strategies and invasive treatment protocols to preserve cultural property for the future. Objects conservators typically specialize in one type of material or class of cultural property, including metals, archaeological artifacts, ethnographic artifacts, glass, and ceramic art. Objects conservation presents many challenges due to their three-dimensional form and composite nature.
The conservation and restoration of shipwreck artifacts is the process of caring for cultural heritage that has been part of a shipwreck. Oftentimes these cultural artifacts have been underwater for a great length of time. Without conservation, most artifacts would perish and important historical data would be lost. In archaeological terms, it is usually the responsibility of an archaeologist and conservator to ensure that material recovered from a shipwreck is properly cared for. The conservation phase is often time-consuming and expensive, which is one of the most important considerations when planning and implementing any action involving the recovery of artifacts from a shipwreck.
The conservation and restoration of wooden furniture is an activity dedicated to the preservation and protection of wooden furniture objects of historical and personal value. When applied to cultural heritage this activity is generally undertaken by a conservator-restorer. Furniture conservation and restoration can be divided into two general areas: structure and finish. Structure generally relates to wood and can be divided into solid, joined, and veneered wood. The finish of furniture can be painted or transparent.
The conservation and restoration of clocks refers to the care given to the physical and functional aspects of time measuring devices featuring "moving hands on a dial face" exclusive of watches. Care for clocks constitutes regulating the external environment, cleaning, winding, lubrication, pest-management, and repairing or replacing mechanical and aesthetic components to preserve or achieve the desired state as specified by the owner. Clocks are typically composed of multiple types of materials such as wood, metal, paint, plastic, etc., which have unique behaviors and environmental interactions, making treatment options complex. The materials used and the complexity of clockwork warrant having a Horological Conservator complete the work.
The conservation and restoration of painting frames is the process through which picture frames are preserved. Frame conservation and restoration includes general cleaning of the frame, as well as in depth processes such as replacing damaged ornamentation, gilding, and toning.
Textile stabilization is a conservation method for fiber and yarn-based cloth intended to mitigate damage, prevent degradation and preserve structural integrity. Stabilization is part of a broad set of techniques in the field of conservation and restoration of textiles typically undertaken by a specialist or textile conservator. Appropriate treatment is determined through risk assessment and close examination of a textile's characteristics and the nature of the damage. Organic and synthetic fibers become weak due to age, handling, and environmental exposure and display physical deterioration such as fraying, planar distortion, loss, and change in surface character. Treatment involves reinforcing tensile strength and reintegration of parts for aesthetic, functional, and historic preservation. Methods can include stitching, darning, reweaving, and the attachment of supports through overlays and underlays. Hand-sewing follows the mantra of “gently does it” using fine needles, supple yarns, and a light touch. Heavily damaged and fragile fabrics often require stabilization through adhesive consolidation, though this is less common. It is essential that conservators consider physical and chemical compatibility along with future treatability in choosing a stabilization technique.
Conservation-restoration of bone, horn, and antler objects involves the processes by which the deterioration of objects either containing or made from bone, horn, and antler is contained and prevented. Their use has been documented throughout history in many societal groups as these materials are durable, plentiful, versatile, and naturally occurring/replenishing.
The conservation and restoration of paintings is carried out by professional painting conservators. Paintings cover a wide range of various mediums, materials, and their supports. Painting types include fine art to decorative and functional objects spanning from acrylics, frescoes, and oil paint on various surfaces, egg tempera on panels and canvas, lacquer painting, water color and more. Knowing the materials of any given painting and its support allows for the proper restoration and conservation practices. All components of a painting will react to its environment differently, and impact the artwork as a whole. These material components along with collections care will determine the longevity of a painting. The first steps to conservation and restoration is preventive conservation followed by active restoration with the artist's intent in mind.
The conservation and restoration of woodblock prints, is the process of caring for and repairing images made from a specific printing process involving using wooden reliefs to stamp or imprint an image onto paper. The process of creating woodblock prints as Asian examples are known, or woodcuts as Western examples are called, has been known for many centuries, and many older prints have experienced aging and deterioration of the paper and colorants used.
The conservation of taxidermy is the ongoing maintenance and preservation of zoological specimens that have been mounted or stuffed for display and study. Taxidermy specimens contain a variety of organic materials, such as fur, bone, feathers, skin, and wood, as well as inorganic materials, such as burlap, glass, and foam. Due to their composite nature, taxidermy specimens require special care and conservation treatments for the different materials.
The conservation-restoration of panel paintings involves preventive and treatment measures taken by paintings conservators to slow deterioration, preserve, and repair damage. Panel paintings consist of a wood support, a ground, and an image layer. They are typically constructed of two or more panels joined together by crossbeam braces which can separate due to age and material instability caused by fluctuations in relative humidity and temperature. These factors compromise structural integrity and can lead to warping and paint flaking. Because wood is particularly susceptible to pest damage, an IPM plan and regulation of the conditions in storage and display are essential. Past treatments that have fallen out of favor because they can cause permanent damage include transfer of the painting onto a new support, planing, and heavy cradling. Today's conservators often have to remediate damage from previous restoration efforts. Modern conservation-restoration techniques favor minimal intervention that accommodates wood's natural tendency to react to environmental changes. Treatments may include applying flexible battens to minimize deformation or simply leaving distortions alone, instead focusing on preventive care to preserve the artwork in its original state.
The conservation and restoration of herbaria includes the preventive care, repair, and restoration of herbarium specimens. Collections of dried plant specimens are collected from their native habitats, identified by experts, pressed, and mounted onto archival paper. Care is taken to make sure major morphological characteristics are visible. Herbaria documentation provides a record of botanical diversity.
The conservation and restoration of wooden artifacts refers to the preservation of art and artifacts made of wood. Conservation and restoration in regards to cultural heritage is completed by a conservator-restorer.
The 'ten agents of deterioration' are a conceptual framework developed by the Canadian Conservation Institute (CCI) used to categorise the major causes of change, loss or damage to cultural heritage objects. Also referred to as the 'agents of change', the framework was first developed in the late 1980s and early 1990s. The defined agents reflect and systematise the main chemical and physical deterioration pathways to which most physical material is subject. They are a major influence on the applied practice of conservation, restoration, and collection management, finding particular use in risk management for cultural heritage collections.