Conservation of textiles
- Sheila Landi
The fragments of ancient textiles recovered from bogs and burials around the world are among the first signs of the technological developments that are the basis of modern civilization. However, they have not always been treated with the respect they deserve, and much information has been lost through indifference on the part of archaeologists and dealers, and even some museum curators who were blind to the cultural significance of textiles. Increasing industrial pollution created by that very same civilization put at risk objects that were at last being recognized as of great historical interest when most museums were short of space and money, and provision for textiles was often particularly poor and overcrowded. As we advance into the 21st century, attitudes towards textiles have changed for the better, but there is still much to be done to encourage investment in the preservation of artifacts that are especially vulnerable to environmental fluctuations, the wear and tear of ordinary use, and poor storage conditions.
As a professional activity textile conservation has its roots in the 1930s when a few European curators began to introduce a more systematic approach to the problems of textile cleaning, repair, and display. After World War II the situation where the curator oversaw the work of a technician was still common in Europe although it steadily shifted to the true professional conservator.
The profession became fully established in the second half of the 20th century, when countries throughout the world became anxious to preserve their textile past from the ravages of climate and environmental pollution. Institutions in London and Amsterdam were at the forefront of the search for new methods and materials, while the Abegg-Stiftung in Riggisburg, Switzerland, adhered much more to the traditional methods for the support of fragile textiles. In Scandinavia the extensive collections of military banners and costume from as early as the 17th century led to the development of new techniques for their safe display, working within a fairly narrow range of options on materials. There were also early developments in the treatment of archaeological textiles as they emerged from bog excavations.
Throughout the world, although the large museums were gathering collections of global textiles, local museums focused on indigenous production from the later 18th century onward, which has led to an emphasis on good storage rather than active intervention. Initially, training was usually “in post” but, as required standards of theoretical knowledge increased, training became more centered in universities and there was an emphasis on the technology of production as a basis for any remedial work. The influence of local conditions and collections on the development of different but equally valid approaches to the treatment of textiles should be appreciated. Even the different ways in which treatment work has been commissioned has led to regional approaches in textile conservation.
Alongside the development of methodology there also grew up a set of ethical considerations that steadily imposed restraints on the more radical types of intervention that were carried out in the early years. But even in this field cultural differences can influence what is considered to be an appropriate course of action. There can be no hard and fast rules. Even the once cardinal rule of reversibility has been recognized as being an impossible goal in some conditions of degradation. Textile fibers, made from organic compounds, are bound to degrade in time, so that slowing down the process as much as is reasonable becomes a primary task. The results of such degradation are manifested in loss of tensile strength, loss of surface texture, the fading of dyes, and the yellowing of white fabric. There is danger from mold, encouraged by high RH and fluctuation of temperature; from high temperatures which dehydrate the fibers; and from dust which harbors microorganisms and encourages the absorption of acidity in the atmosphere. General atmospheric pollution and display in high light levels have accelerated this process in many cases, so that now, even with the possibility of remedial conservation, only the best preventive conservation can preserve our most valuable heritage.
One aim of the profession, beyond preserving what is left of the original object, is to gather information about the technology and purpose of its construction to add to the general pool of knowledge, the pursuit of the so-called true nature of the object. This aim may involve the removal of old repairs and additions, but there is an alternative point of view, with growing influence. The textile with all its additions and repairs is considered to have become a social object whose passage through history should also be preserved. There is a third point of view, a scientific perspective that derives the value of an object from the analysis of the materials from which it is made. These varying levels of interest have to be accommodated by the conservator, with an ever increasing importance of cost in mind as well.
Nothing lasts forever; conservators in any age can only do their best with what is available at the time, knowing that in due course someone else will have to take up where they left off. If a good record of what has been done accompanies the object, it will make the future task all the easier.
See also Textile.
2. Assessment and preventive conservation.
Preventive conservation comprises storage, display, and control of the agents of decay in the environment whereas remedial conservation means active intervention in the physical state of the object by cleaning, repair, and support. Because the remedial conservation process is expensive in terms of labor, in spite of advances in techniques there has been a swing towards preventive rather than remedial interventions, as being more cost effective.
The basis of all decisions on conservation work is examination to determine the content and condition of the materials used in the manufacture of the object. The fundamental unit in a textile is a fiber. Fibers come from plant and animal sources, giving rise to the division between cellulose (cotton, linen, hemp, and other plant fibers) and protein in those derived from the silk worm and various animals that yield hair (see Textile §I, 1). There are many sources of fibers that were spun into yarn and woven together but the most common fibers are linen, cotton, silk, and wool, from which most of the finest textile objects were made. Many other materials can be found associated with the textile in the same object, such as metal, wood, paint, parchment, jewels, ivory, bone, glass, feathers, etc. These must be identified as their presence can prohibit certain courses of action or require advice to be sought from other areas of expertise
Beyond the use of a microscope or chemical reaction, identifying the origin of the object in terms of period and area of the world can often help to establish whether the fiber is of cellulosic or proteinaceous origin, but it is also a factor in decisions involving the cultural significance of any intervention proposed. The makeup of all subsidiary components must also be identified to avoid accidents. During this process of identification, threads used in construction should be noted with any changes indicating an alteration. Stitch holes no longer occupied, changes in color, seams or crease lines in strange places, or an alien fabric can all indicate alterations that may or may not be acceptable in present circumstances. Photography is normal at this stage to record the condition before any work is done.
Once the textile content has been determined the condition of the fiber structure and amount of dirt will then exercise a strong influence on the degree of and cleaning methods necessary. Dirt has many origins and can be on the surface or deeply ingrained. Removal may involve only mechanical means such as vacuum cleaning, or the use of liquid, either water or solvent, together with reagents and surfactants.
It can be broadly stated that cellulose is in danger from acidic conditions while the reverse is true of protein which reacts badly to alkali conditions. Whatever action has to be taken a return to a neutral position is essential.
Ideally, storage areas should be fully air conditioned, with stringent specifications for the filtration of dust particles and the removal of such harmful gases as sulfur and nitrogen dioxides. In any case, areas should be kept as dust free as possible; they should be dark except for practical reasons, free from damp with relative humidity kept level between 45 percent and 55 percent and free from atmospheric pollution.
Many specialist firms provide storage containers and display cabinets made with the most suitable materials to prevent contamination from off-gassing, and it is generally agreed that all packing materials such as boxes, rollers, and tissue paper should be acid free. Envelopes of inert polyester film and glassine have become available, or can be custom made, and used for smaller objects which are then visible without having to be unpacked, which is a great advantage. Polythene should be avoided for this purpose as it degrades within a comparatively short time, attracts dust through static, and can trap moisture.
Shelving, drawers, and boxes should be designed so that objects can be stored unfolded, as permanent creases can be created otherwise. Many shallow units are better than larger, deeper ones, to avoid the temptation to place too many objects on top of each other. Damage from abrasion and by surface decoration becoming entangled can be the result of moving unprotected objects in close proximity to one another.
Larger flat textiles should be rolled, rather than folded, with the outside of the object kept on the outside of the roll and with the direction of the warp. Certain types of weave structure, such as tapestry, velvet, and most carpets, are particularly weak in the direction of the weft. In the case of a piled weave such as knotted carpets or velvet the direction of the roll should also follow the direction of the pile to avoid crushing it.
Before starting to roll a textile a clean dust sheet should be spread on a flat surface, large enough for the object, with extra at each end, and with the object spread as squarely as possible and face down to avoid closing surface decoration in on itself. A roller of sufficient length and suitable diameter should be placed at one end and then the object, together with the surplus sheet, lifted over and tucked in firmly. Keep rolling evenly and straight, avoiding a spiral towards one end, any lining present being tucked back into the roll as you go. Finish by wrapping the roll in the other end of the sheet. Flat straps should be pinned or fixed with Velcro round the roll, not tied.
Three-dimensional objects such as costume can present special problems of support to prevent damage from creasing from being folded or to sleeves or bodices when they collapse in on themselves. They need to be padded out with acid-free tissue or wadding of some sort, even when hung rather than laid flat. Accessories need individual support with shapes cut in inert foam such as Ethafoam, rather than stuffed with acid-free tissue, which far too easily can distort the shape of the object rather than maintain it.
There are two approaches to the display of textiles; one regards them almost as sculpture, while the other emphasizes the role they played in society. The choice has a big impact on presentation and consequently on means of support. For general purposes textiles can be divided into three groups: large, flat textiles that can be suspended in a vertical position; smaller flat objects such as embroidered panels or examples of weave structure; and free-standing, three-dimensional objects that need support to maintain their shape. Costume tends to form a group of its own, needing special techniques.
Environmental conditions inside enclosed spaces of showcases, frames, and galleries should largely be governed by the same range of criteria used for storage. Light levels are more difficult to regulate in public areas but should be maintained as near to the ideal of 50 lux as possible. Concentrated light on small areas must be avoided as this can produce differential fading and weakening of fiber structure. Each object has a finite life in terms of lux hours of exposure to light, damage being accumulative from all parts of the waveband, but greatest in the UV region. Thus, the intensity and nature of the light source can be regulated in accordance with the role being played by the textile, whether it is on long-term display or in a temporary exhibition. When on open display, as in the staterooms of great houses and other institutional open spaces, other problems, such as a natural light source from a window, fluctuating temperatures and humidity, and drafts and dust created by passing visitors and their proximity to the objects, have to be considered.
When hanging a large textile such as a tapestry it is important to make sure that the weave structure has sufficient support and a lining that will prevent stress. Suspension must be continuous, such as with a batten in a sleeve or Velcro hook and loop strip, rather than from points such as studs or rings. These can result in local permanent malformation. If a containing frame is involved it may be necessary to fix down the sides, when Velcro is the best answer, but the bottom should be left free to find its own level whenever possible
Smaller items are often stitched to a rigid, fabric-covered board and then framed. The use of an open stretcher in the past left the textile in danger of mechanical damage and the passage of airborne dust particles. The board and covering provide protection and a buffer against changes in relative humidity. The board, which may be lightly padded, should be covered with a strong fabric of a suitable color to which the object can be stitched after being pinned out under slight tension to prevent it from dropping under its own weight over the course of time. Depending on size and nature another option is to sandwich the object between two rigid plates, sinking the object into a soft surface to avoid crushing any surface detail. For the largest objects in this category stitching can be run through the center and strategic pattern lines as well as round the edges. Only the most stable materials should be chosen both for board and the padding. Many composition boards can give off harmful compounds such as formaldehyde in enclosed conditions.
Objects such as church vestments, costume, or upholstered furniture present a greater dilemma since the way they were constructed is often as important as the materials from which they were made. The alternative to support from the reverse is to cover the front with a semi-transparent material, but this is only a last resort as so much detail of surface texture can be lost. Covering with nylon tulle has been used to protect surfaces such as curtains that are open to abrasion from the passing visitor, but while it can help to some degree it is important to remember that nylon does not have a long life in exposed conditions.
Mounting costume and the achievement of a characteristic shape on a dummy is not easy without funding for specialist figures. The field of manufacture for bespoke figures has broadened in the past years, but these are not always affordable or available. Resort to dummies which have to be altered in some way to produce the period stance correct for the costume is common.
In many cultures and periods the human body has been distorted into preconceived notions of fashionable beauty by corsets of extreme rigidity, and these now provide valuable clues to the correct silhouette for each period. The most obvious difference between the European female figure of the 18th and 19th centuries and the present day is the position of the bust, which was pushed up to sit on top of the thorax, resulting in a silhouette that requires considerable alteration to a modern-day mannequin. The intent of the display determines the pose of the mannequin, but extremes of posture should always be avoided, to prevent distortions being formed in the structure of the piece.
It is always the responsibility of the conservator to ensure that the designer of the exhibition is aware of such conservation requirements.
3. Remedial treatment.
It is important for the conservator to discuss with the client the expectations they might have. Although the techniques available to the conservator have expanded over the years, their use can be restricted, because of either availability or cultural attitudes. The removal of old repairs that do not actively distort or otherwise damage the object or the introduction of support fabrics that is made difficult by the presence of original stitching are areas where caution should be exercised and interested parties should be consulted before any action is taken.
The choice of techniques and materials must respect the nature of the textile and be identifiable on close examination. It is no longer acceptable to reweave missing areas in a tapestry, nor to replace embroidery that has worn away, nor to cut out and remount embroidery on a new material. While traditional methods using sewing techniques still dominate textile conservation, it is clear that some conditions of fragility cannot be treated in this way; they can only be helped by using an adhesive. Once a highly controversial technique, the use of adhesives has slowly become respectable as more people have been confronted with the problem, but it is an area where industrial production can influence the choice of adhesive in use. Consolidation, in the sense of creating a continuous film of resin to hold brittle fibers together, has largely been abandoned after a number of experiments proved unsuccessful in the aim of increasing flexibility without profoundly changing the nature of the textile. It is, of course, possible that a future industrial process will arise that would achieve the desired result within the economic and practical limitations of the conservation world.
Both sewing and adhesive techniques may be used on the same object, according to the kind of stress to which the repair will be subjected.
Cleaning is the most irreversible of all conservation procedures and thus should be undertaken only if absolutely necessary. Dirt obscures colors and textures and deposits such as rust (iron oxide) can actively attack the chemical composition of the textile, and gritty dust can cut through delicate yarn, causing breakages. The presence of any of these conditions and the effect they have had on the strength of the substrate will determine the method and materials to be used.
To remove any of these disfigurations agitation of some sort is required, which can be achieved by the use of brushes or controlled vacuum and, increasingly, by the use of smoke sponges, a product that absorbs fine particles into its own molecular structure. When using such means close observation is needed to control the strength of abrasion or suction in order not to remove textile fibers as well as dirt. At times, a protective layer of fine tulle or monofilament nylon net can be introduced between the textile surface and vacuum nozzle. A vacuum cleaner with controllable suction is essential.
Some types of weave structure and decoration are suitable for washing in deionized water with the addition of detergent and other reagents that control pH, which is usually the most efficient way of removing dirt. Indeed, any stains that are the product of accidents with water can only be removed by more water as solvents seldom have any affect.
Before washing, tests must be made to make sure any dye is fast in water. Single-color fabrics may be allowed to bleed a little without prejudice, but if it is very fugitive the intensity of color will be affected. In order to keep the textile under control and as flat as possible during the process a washing table may be used, to provide a flat surface that can be tilted for drainage, or an open mesh through which surplus water can be sucked away with a pump. The object should be supported separately on a flexible film, such as polythene or Melinex, which can be used to make a sandwich which can be turned over to give access to the reverse. This kind of support can be used for objects that are larger than the work surface available, coupled with plastic rollers on which to take up the surplus length. Agitation to the surface is supplied by sponges or brushes worked gently over the surface which may be protected by a layer of tulle or stronger net. The washing is completed with thorough rinsing in deionized water, which is drained away before the object is laid out to dry, with the correct weave structure maintained. The wet textile should only be moved on a skin of water before the surplus is absorbed by towels. Weaves such as damask or any flat textile without surface decoration should be laid out face down to dry on un-textured plastic, where the smooth surface will ensure a perfect finish.
Any textile that has a finish, dyes, or compound weave structures that may be damaged by contact with water can only be spot or solvent cleaned. Silk satin weaves and brocades, velvet, glazed cotton, or wool and objects that contain several different types of weave fall into this category.
If solvent cleaning is necessary the best results can only be achieved in a proper dry-cleaning machine, but most objects are not strong enough to withstand the violent mechanical action of commercial machines. In recent years the availability of dry-cleaning fluids has greatly decreased with the growing awareness of the effect they have on the environment. Many solvents once in common use are now either banned altogether or can only be used in restricted circumstances. It is still possible to use White Spirit (Stoddard’s Solvent) and industrial methylated spirit (IMS) in the UK, but local regulations must be consulted whenever such products are used in quantity. All apparatus used with solvents should be of glass, stainless steel, or enamel. Plastic is unsuitable as it may be attacked by the solvent. Protective gloves and solvent masks must be worn.
Metal components in an object can often be brightened by detergent in water or by a solvent such as IMS, but heavy corrosion products can only be removed with an acid or alkali, which will damage surrounding textile fibers. Thus cleaning metal thread has become limited by ethical considerations.
(ii) Repair and support.
After an object has been cleaned, any structural weakness can be repaired and strengthened, either by traditional sewing methods or with the use of adhesives. Frequently both methods will be used on the same object for different purposes
Repair implies a process of tidying up rather than full-scale conservation, such as the replacement of broken stitching in seams, for example, sewing or sticking back loose decorative features, or applying local support by darning or couching in an otherwise strong object. Darning is less common than in the past, when it was used for domestic repairs, but it still has a place in conservation in repairing local mechanical damage in a fabric that is basically sound or when the object is double-sided.
The stitch most commonly used in conservation is couching (see fig. D13). A support fabric is chosen, of similar color and texture to the original but slightly lighter in weight, and either mounted on a frame or laid flat on a work surface. The damaged area of the object is placed over it, with the warp and weft arranged in line with that of the support, maintaining the support at a lesser tension than the object. Starting at one side of the area, a long thread is laid parallel to the weave, across the damaged area. Small stab stitches are made over the laid thread at equidistant points along its length. A second thread is laid alongside the first, at a distance suitable to the type of damage found (a typical distance would be 10 or 12 mm), and the process repeated, staggering the stab stitches in a brick pattern. Provided that the area is fully covered, this system provides an excellent way of supporting a weakened textile with the minimum of interference, while any areas of loss will be filled in by the backing fabric.
Embroidery frames of the beam type, with slats and pegs for tensioning, are frequently employed, but for small areas a padded frame is preferable. This is made by cutting a hole of suitable size in a board, which is then padded and tightly covered with cloth taken round to the back of the board. The object can be placed over the space, to be worked on directly, or a new support can be pinned or tacked out under tension before the object is placed over it. The frame can be supported over the edge of a table or on trestles to enable the worker to use one hand above and one below in the usual way. The round frame, which encloses only part of the fabric, should never be used.
For tapestries it has become common to use warp couching, with the exposed warp of the tapestry as the laid thread and colored yarn as the over-stitch with varying density as a visual replacement for loss of weft. The stitches are worked through a layer of linen placed behind the area in a number of ways. There are other methods and materials in use, in response to problems created by size and the type of damage sustained by tapestries.
Animal glues and wheat or starch pastes have been used in the manufacture of composite textile objects for many centuries. They have also been used for purposes of repair, though not always with the happiest of results. The fact that starch pastes attract insects as a source of food must be a disadvantage and water-based adhesives can affect dyes in the object that are not fast to water. Modern glues based on rubber have been even more disastrous in their effects, becoming black and insoluble in a comparatively short space of time.
Modern alternative adhesives have been sought. Flexibility is the prime quality required, with long-term stability to retain the possibility of reversal, together with a method of application that avoids total penetration of the weave structure. Choice has fallen on the class of thermoplastics based on polyvinyl acetate (PVA) or on acrylic resins, which can be applied to a separate fabric, allowed to dry, and then attached to the reverse of the object using heat and pressure. A limiting factor is the melting temperature, which must be low enough not to damage the object, but not so low that unprotected adhesive remains tacky in normal, warm, ambient temperatures. The safe range lies between 60° and 75° C. Historically this system became possible in the late 1950s, as industrial products became available in which flexibility was given to a rigid plastic by the use of a co-polymer, rather than a plasticizer.
To apply a support using a thermoplastic adhesive a flat work surface is needed, slightly softened with a sheet of brushed cotton and then covered with a material such as Melinex that is resistant to heat and adhesives. If the adhesive Beva 371 is used then only silicone paper or Melinex with a silicone surface is safe. A domestic iron can be used, set at a controlled temperature suitable for the particular adhesive, with silicone paper as a release layer between the iron and the adhesive. Alternatively, a vacuum hot-table may be used to provide, in one action, both the heat and pressure required over the whole surface.
With age, textile fibers may become either stiff and brittle or soft and powdery, eventually reaching a stage when support by another fabric ceases to be sufficient and either complete isolation or a consolidant is needed. The consolidating substance must not alter the color of the original, nor stiffen with age. Also, to meet ethical requirements, it must remain soluble so it can be removed if necessary. As already stated, no product has yet become available that entirely meets these criteria. Since the result of consolidation seems to be an increase in brittleness, even when tensile strength has been improved, it remains a last resort.
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