Textiles and Fabrics: Conservation and Preservation
A textile is a binary system of fibers or other materials worked into threads. In essence a textile is formed by weaving, but the term can also be used more generically and thus covers flexible products made in other techniques, as, for instance, twining, needle binding, knotting, and knitting. Felting and basketry are also techniques related to textiles. Thus, textiles can be seen as one part of an overall cloth culture, which may include many different materials and techniques (Harris 2012).
Around the world and throughout time, humans have created textiles by exploiting different natural resources and inventing tools and methodologies to change these resources into a viable product. Some areas are rich in traditional textile resources, like materials for fibers, dyes, and tools, but also in less resource plentiful areas, humans have found solutions for fulfilling the demand for textiles.
Until very recent times, textiles were primarily made from natural fibers of either plant or animal origin. The most well-known plant fibers are flax, hemp, nettle, and cotton, while the most well-known animal fibers are sheep wool and silk. Like any perishable organic material, these fibers are subject to rapid decomposition in archaeological contexts, and their preservation requires special conditions to prohibit their destruction by microorganisms.
Key Issues/Current Debates/Future Directions/Examples
Environmental conditions affect the survival of plant and animal fiber materials in various ways. In general, an acidic environment favors the preservation of proteinaceous fibers, while a alcaline environment does the same for fibers of vegetal origin. As most degradation requires the presence of air, many textiles have been found in contexts where anaerobic and/or waterlogged conditions occur. Other conditions like extreme dryness or permanent frost; the presence of salt; exposure to fire, which leads to the creation of carbonized samples; or through mineralization when coming into contact with metal salts have also preserved many textiles.
The find context influences the preservation of archaeological textiles. In Europe, most textile remains have been found in connection with burials, such as costumes, wrappings of human remains and/or grave goods, furnishing, and other utility textiles. In inhumation graves, the organic materials are often exposed to heavy and fast degradation, and, in most cases, it takes special conditions as, for instance, the presence of metal salts from copper or iron to prevent the degradation (e.g., Bender Jørgensen 1992; Rast-Eicher 2008; Gleba & Mannering 2012). Though these textiles are often very small and in a stage where further organic analyses are excluded, they still offer due to their number and firm structure an important source to European textile technology. In dry climates as in Egypt, many textiles have been preserved by desiccation and aided by the burial custom of embalming the dead. In a similar way, the special tradition of embalming and placing the dead in caves, which was performed in the pre-Columbian Inca kingdom, has preserved many colorful textiles made of cotton and wool in South America. Frozen environments like the Norse burials in Greenland have left fabrics almost unaltered, and in the recent years, the melting of glaciers in, for instance, Switzerland and Norway have also revealed well-preserved textile finds. In Denmark, the waterlogged, anaerobic, and acidic environment in burial mounds has favored the preservation of a large collection of complete Bronze Age textiles and costumes.
The scarcity and poor preservation of archaeological textiles are two factors usually cited for the absence of focus on textile studies. Although valid to a certain extent, such reasoning has obscured the fact that textiles are much more abundant in archaeological contexts than generally assumed and should, whenever present, be studied in the same way as any other archaeological finds.
Textile Research and Scientific Analyses
Textiles have an enormous potential in archaeological research, being able to tell about social, chronological, and cultural aspects of past societies, and at the same time providing us with a unique opportunity to come very close to the prehistoric or historic individual. Substantial information about past societies can be gained from the study of textiles, but this information depends on the analytical tools and methods used. A textile contains information about the process and the tools used in the various stage of its production. The decoding of a textile is imperative for the understanding of the many different processes involved in its production, and the methods may vary according to the state of preservation (Andersson Strand et al. 2010). For instance, the processing of a fiber material from the source to the final thread and the weaving and sewing will not only tell about breeding systems and the technological knowledge of that time but also indicate more subtle information about visual preferences and human desires.
Fiber identification is an important starting point in textile research as it indicates the properties of this material as well as the possible use. The identification of fibers is in most cases based on morphological characteristics performed by various types of microscopy. The optical microscopy is the most basic tool which together with scanning electron microscopy (SEM) enables precise photographing and measuring. In these cases sampling is necessary. Fiber identification can be difficult in cases of highly aged and deteriorated samples where fiber characteristics have been changed and/or where sampling is complicated by the fragility or the scarcity of the fibers. In such cases, scanning electron microscopy is especially useful and combined with energy dispersive X-ray spectroscopy (SEM/EDX) inorganic elements in the fibers such as pigments, mordants, and salts, and proteins in animal fibers can also be analyzed. Transmitted electron microscopy (TEM) can provide information on the internal fiber structure such as the pigmentation of wool fibers. Gas chromatography/mass spectrometry (GC/MS) and infrared microspectroscopy (FTIR) are useful analytical methods for the identification of resins, oils, and balsams that can have been applied to textiles. High-performance liquid chromatography (HPLC) is used to obtain information about dyes or dye components that are not visually detectable anymore. Especially, dye analysis provides important information to the archaeological interpretation that characterize visual preferences, technology, and exchange of know-how and goods (Vanden Berghe et al. 2009). Radiocarbon dating (14C) can be used for textiles from disturbed contexts or contexts where no other datable object exists (Mannering et al. 2010). Textile materials are, in general, well suited and reliable for 14C dating, although the presence of conservation substances should be evaluated before sampling. Stable isotopes can reveal facts about the nutrition (Wilson et al. 2001), while strontium isotopic analysis, which has now been adapted to fibrous material, can reveal whether the textiles are of local or nonlocal origin (Frei et al. 2008). DNA sequencing is useful for the identification of specific species, which are otherwise hard to identify, but the results highly depend on the preservation conditions (Ørsted Brandt et al. 2011). Detection of species of animal origin can also be done with mass spectrometry-based protein sequencing (MSPS) (Schmidt et al. 2011).
The constant improvement of scientific analytical methods and the development of new ones will often inspire further analyses. Yet, most analytical tools require sampling, and it is important to develop more nondestructive methods in order to secure our common world heritage, and to improve working conditions and the scientific outcome. The importance of taking samples should be evaluated prior to analysis, and sampling should preferably be done before any contamination has occurred. Accurate documentation, preferably by photographs, of where samples have been taken is imperative.
Preservation and Conservation
The aim of an active conservation treatment is to improve the condition of the textile by trying to eliminate some of the causes of deterioration, and the aim of preventive conservation is to slow down the rate of further degradation (Skals 1996). Textiles preserved in archaeological contexts are often weak and tend to be fragile and decompose easily when exposed to changes in the climatic conditions and to touching and handling. A general rule is that dry textiles should be kept dry, wet textiles kept wet, and textiles should be stored in a cool place until the conservation treatment can commence. Adding consolidants during retrieval or biocides to avoid bacterial or fungus growth should be avoided as future scientific analyses thereby will be complicated or prevented (Gillis & Nosch 2007).
The method of drying waterlogged archaeological textiles and the questions of pretreatment with lubricating additives such as polyethylene glycol (PEG) or glycerol are factors which has been the focus of much discussion and research. Freeze drying has been evaluated as the gentlest form of drying. It can be done under vacuum or at atmospheric pressure. The discussions regarding pretreatment are somewhat unresolved because the additives in theory are soluble and the treatment reversible. Nevertheless, it can be very difficult to completely remove additives from archaeological fibers. Lubricants are often added to waterlogged wood to replace the water that has filled the empty spaces in the cell structure. Adding lubricants to textile fibers with the aim of replacing the water in the fiber structure is a different matter. The molecular structure is different from wood, and the empty spaces inside fibers are very tiny. Furthermore, the yarn structure, consisting of many fine fibers twisted together, will cause the liquid additives to run into all the air spaces and coat the fibers. Completely removing them is impossible without much damaging manipulation of the textiles. Also future scientific analyses will be unreliable. Avoiding the use of lubricants is therefore recommended (Peacock 2005).
Cleaning of textiles is an irreversible process, and the effect of cleaning on the condition of the textile must be evaluated before a treatment is chosen. Thorough cleaning of wet archaeological textiles prior to drying should be avoided as should also wet cleaning of dry archaeological textiles. Dirt can be the cause of long-term degradation but also be part of the history of the object. Likewise, the cleaning process may remove less stable substances like dyes and paint which may not be visible to the naked eye, or pollen assemblages stored in the textile, which in turn contain information about human activities and the environment.
The long-term preservation of textiles will be enhanced by good, clean, and cool storage. Fragile textiles should be supported, and shelves and drawers should be well fixed to eliminate mechanical damage. The textiles should be protected from deteriorating effects of light, heat, and high humidity, and regular monitoring for insect infestation is recommended.
Due to the fragile nature of textiles, they will inevitably degrade. Careful handling and ideal storage are preventive methods that can slow down the degradation, but they can never prohibit or stop it. Therefore, it is of utmost importance that archaeological textiles are analyzed and studied when possible. In this work, a useful tool is high-resolution digital photography which provides accurate documentation of the object and its condition at a certain time. At the same time, this technique also opens for a wider scientific use and dissemination of these fragile objects, which reaches beyond their physical presence.
Textile research is a worldwide occupation which is performed within many different disciplines. This is also the case within archaeological textile research where the theoretical and methodological approach, to a large extent, depends on the research traditions in the different geographical and cultural historical areas. Research in archaeological textiles are performed by, among others, archaeologist, historians, art historians, textile designers, conservators, and crafts people, and each in their way, they are able to contribute with important aspects to the understanding of the production and use of textiles.
Textiles and fabrics are an important part of our common world heritage. Most cultures and peoples around the world use textiles for multiple purposes and the same are true for past societies. Common for this worldwide endeavor is first and foremost the wish to keep warm and comfortable, but textiles also have an important role in expressing who we are – our gender, age, family affiliation, status, occupation, religion, and ethnicity. Knowledge of textile history is hence a key to our understanding of a multitude of human issues.
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