Conservation and restoration of textiles
The conservation and restoration of textiles refers to the processes by which textiles are cared for and maintained to be preserved from future damage. The field falls under the category of art conservation, heritage conservation as well as library preservation, depending on the type of collection. The concept of textile preservation applies to a wide range of artifacts, including tapestries, carpets, quilts, clothing, flags and curtains, as well as objects which "contain" textiles, such as upholstered furniture, dolls, and accessories such as fans, parasols, gloves and hats or bonnets. Many of these artifacts require specialized care, often by a professional conservator.
Collections
Historic textile collections fall into three general categories: museums, historic societies/locations, and private collections. The needs of each of these locations will vary. A private collection, for instance, is unlikely to have as high a traffic flow as a museum, and may thus be able to take preservation steps that a public museum cannot, such as minimizing light exposure over long periods of time. Venue-specific issues may also arise. For instance, many historic homes do not have climate control and rely on natural light to display their furnishings, both factors that may contribute to textile decay.Environment
The chief cause for decay in textiles is almost always the environment in which they are stored. Light, temperature, and humidity can all contribute to a textile's health or deterioration, depending on their intensity. Additionally, pests, chemicals, and pollutants may also cause damage to an antique fabric. Airborne chemicals, such as smog or cigarette smoke are also harmful to the textiles, and should be avoided if at all possible. In museum or otherwise specialist collections, high-efficiency air filters are typically installed throughout the building to reduce the presence of airborne chemicals that may stain, discolor, or weaken fabrics.Light
can have a variety of effects on textiles over time. In some cases, it may contribute to fading or discoloration, but the primary damage caused to textiles by light is fiber weakness caused by prolonged exposure to ultraviolet and infrared lighting. Ideally, textiles should be stored or displayed in as little light as possible, and preferably in total darkness. However, as this is impractical for display and care of the piece, knowledge of UV exposure limits and how a textile can be handled under safe amounts of lighting are also necessary for conservation.Natural light is the most common source of ultraviolet light, and as such, care should be taken to avoid exposure to direct sunlight at all costs, and indirect sunlight whenever possible. This may mean storing or displaying textiles in an area without windows, or with blackout curtains, which can be drawn whenever the room is not in use. If a room relies on natural light, UV screens or coatings can be applied to the windows to block harmful rays while still allowing light to pass through. These filters should be checked periodically, however, as they have a limited lifespan and may need to be replaced every few years.
Fluorescent and halogen-produced light can also produce large amounts of UV radiation, though filters which fit over the bulbs are available to limit the damaging light. These filters are typically replaced when the bulbs are changed.
One advantage of fluorescent lights is that they produce little heat, which may also be harmful to textiles. Incandescent lights produce a large amount of heat in addition to large quantities of infrared radiation, which is likewise damaging to the fibers in antique textiles. If incandescent lights must be used, they should be placed far enough away from display cases that their heat does not affect the contents.
In the case of particularly delicate textiles, display organizers might consider motion-activated or timed lighting, or lighting controlled though a visitor-activated switch, which would allow the textiles to remain in darkness when not under view. All textiles should be displayed on a rotating schedule, allowing them a few months of display, then the rest of the year in dark storage, to prolong their life.
Climate
Heat and humidity can both contribute and a textile's deterioration. However, excessive dryness may also cause damage, especially to elastic fibers, such as wool, which rely on some amount of moisture to maintain their flexibility. Additionally, temperature and humidity should be kept as constant as possible; changes in either of these may cause the textile fibers to expand and contract, which, over time, can also cause damage and deterioration to the textile. For this reason, both storage and display areas should be fitted with monitoring equipment to gauge the temperature and humidity of rooms, display cases, enclosed storage facilities, and work areas.Ideally, temperature should be kept around, though some slight fluctuation in either direction is permissible, as long as it occurs gradually. For instance, temperature may be slightly lower in winter to save energy costs, but the change should be effected slowly, so as not to place the fibers under undue stress.
As for humidity, the preservationist or conservator should aim for a relative humidity of 50%, though, as with temperature, some small fluctuation is allowable, as long as it occurs gradually. In enclosed display or storage cases, humidity can be somewhat maintained through the use of silica gel crystals. These crystals should not be placed in contact with the textiles, but may be placed in breathable muslin bags and hung inside the case to maintain a constant humidity; they should be monitored periodically, however, to be sure that they are working.
In areas where climate control is unavailable, the conservator can still moderate the temperature and relative humidity through use of fans, humidifiers and dehumidifiers, and portable heating or cooling units.
In addition to temperature and humidity, airflow is also a concern for textile preservation. Textiles should never be sealed in plastic or other air-tight casing unless it is part of a treatment or cleaning process. Proper circulation, combined with the suggested humidity, will help to prevent the growth of mold and mildew, which may stain or weaken antique textiles.
Pests
Pests are another significant threat to textile collections, as there are a number of creatures that can cause damage to fibres. Among the most common are clothes moths, carpet beetles, silverfish, firebrats and rodents.Clothes moths are attracted to protein fibres, and so are especially drawn to silk, wool, and feathers. An infestation might be identified through the evidence of white cocoons on the textiles, or of sighting the insects themselves. They are roughly long and white in colour.
Like clothes moths, carpet beetles are likewise drawn to proteins and can be quite destructive. Evidence of an infestation may take the form of chewed holes, carcasses, or larvae, which appear as small pale worm-like insects.
Silverfish and firebrats are related insects that consume starch, usually found in sizing or other treatments applied to fabrics, as well as plant-based textiles such as linen and cotton. Both are attracted to dark, moist climates, though silverfish prefer cooler temperatures, while firebrats tend towards warmer. Both are about in length and either light or dark in colouring, depending on which type is present.
Rodent infestations can be identified in the usual ways, such as seeing droppings, nests, or comparatively large chewed areas of textile where they have caused damage.
In all cases, chemical means of pest control should be avoided if possible, not only due to harm to humans who come in contact with them but because the chemicals may cause damage to the very textiles the conservator is trying to save. For rodents, snap traps may be effective, and if needed, a professional exterminator should be called. Poison baited traps should be avoided, as the rodent could die somewhere inaccessible, and provide a breeding ground for further pests. In the case of a rodent infestation, all access points to the room through which they might be entering should also be located and sealed if possible.
For insects, keeping clean storage, display, and work environment is the best method of prevention. Sticky traps around doors, windows, and display cases may be useful for monitoring the insect population. Furthermore, the population of carnivorous insects, such as spiders, should be observed. While such insects are not harmful to textiles by themselves, they may indicate another population of insects which are.
If the infestation can be limited to one or a few pieces, the insects may be killed through freezing of the object. The textile should be wrapped in plastic and vacuum-sealed, then brought to a freezing temperature as quickly as possible, to prevent the insects from adjusting to the cold. The object may be left frozen for several days but should be brought slowly back up to room temperature to avoid further damage. While this method should kill adults, it may not destroy any eggs that are present.
If chemical means must be employed, it would be best to consult with a professional conservator to be certain that the treatment will not harm the textiles themselves.
Even if no signs of an infestation are present, textiles should still be inspected periodically to be certain that there is no outbreak that has gone unobserved. Additionally, when dealing with a new acquisition that shows signs of insect damage, the specimen should be quarantined until it can be determined whether the insects are still present before introducing it to the rest of the collection.
Textile instability
In some cases, the textiles are weakened not by outside causes such as light or pests, but by chemical reactions taking place within the fabric itself, such as the oxidation of iron-based mordants over time, which can cause darkening and discolouration in the surrounding fibres.One example which is cited frequently throughout the literature is the case of shattered silk. During the late 19th and early 20th centuries, many silk manufacturers treated their fabrics with metallic salts to improve their drape and feel; as silk was priced by weight, this process also replaced some of the considerable weight lost through the removal of sericin from silk fibres in the degumming process; the resulting fabric was known as weighted silk. However, as the fabrics age, the metals in the fibres accelerate their decay and cause them to become extremely brittle, an effect sped up in part by the addition of 10–15% weight in metallic salt added to some fabrics by manufacturers. This has the effect of shredding, or "shattering", the silk fibre, with the environment and conservation of the textile contributing very little to prevent this deterioration, though exposure to light may accelerate it even further.
Textile preservationists should be familiar with their collections and the history and provenance of their pieces. Chemical tests can reveal the types of dyes and mordants used, as well as any other treatments applied to the fabric. Such knowledge can lead to the prevention of further decay by learning which pieces need to be handled with particular care.