N. King Smith and M. Myers
Although the word textile literally means ‘woven’ and a ‘woven fabric’, it has come to encompass materials produced by a variety of techniques including knotting, knitting, lace making, braiding and felting. Methods used for preserving textiles are many and varied and depend on the nature of the textile material and its chemical and physical condition.
Although the longevity of textile materials is determined largely by how well they are looked after, the survival of ancient textiles is usually attributed to good fortune rather than to the application of particular treatments or to careful management. Often fortuitous storage conditions, as a result of materials being forgotten, lost or buried, are responsible for their survival.
A qualified conservator is the best source of advice concerning the preservation of textile collections. As a first step however, it is necessary to understand the materials themselves.
Until modern times all textiles were made from fibres drawn from natural sources such as protein-based animal fibres (wool and silk) and cellulose-based vegetable fibres (hemp, jute, flax and cotton). These materials have been used in textile manufacture for thousands of years, following the development of spinning and weaving technology.
In the early 19th century attempts were made to produce fibres in the laboratory. Initial attempts that involved the dissolution and reforming of natural materials had only limited success. By the early 20th century, some semi-synthetic fibres, such as casein (protein-based) and rayon (cellulose-based), had been produced commercially. Rayon is a generic term which covers a variety of fibres including cuprammonium rayon and viscose rayon. Fabrics derived from rayon are likely to be found as part of a textile collection while casein-based textiles are less likely to be encountered.
It was not until the 20th century and the development of the petrochemical industry that materials other than those from natural sources were used to produce textiles on a large scale. Examples of fully synthetic fibres developed in the 1940s include polyesters (‘terylene’, ‘dacron’), polyamides (‘nylon’) and acrylics (‘acrilan’, ‘orlon’).
To modify the properties of the individual constituents, blended fabrics have been developed. Two or more fibres are blended before they are spun into yarns. In combination or union textiles, individual yarns of one fibre type are interwoven with yarns of another type, again leading to the production of fabrics with modified properties. Polycotton is a good example where the qualities of absorption and coolness of cotton are combined with polyester for strength and non-creasing properties. The addition of acrylic fibres to other fibre types leads to an increase in the softness and warmth of the resultant fabric.
The identification of textile fibres is important because different fibre types require different conservation treatments. Optical microscopic examination and/or Fourier Transform infrared (FTIR) spectroscopic analysis of representative fibres are the most conclusive methods of identification. There are numerous texts available which describe the characteristic features that allow fibre types to be optically differentiated (Catling and Grayson 1982, The Textile Institute 1970).
Take care when selecting fibres for identification as the features of degraded fibres may differ from those of corresponding undegraded fibres. Careful sampling and examination are essential for accurate identifications. In many cases the condition of a textile can also be determined during this examination and identification stage.
This section on weave structures, finishes and dyes is summarised from Landi (1985). To make a woven textile the fibres are prepared for the rigorous treatments involved in weaving. Fibres from a bulk supply are twisted to form a continuous thread. The resultant thread can be tightly or loosely spun to produce materials of differing densities, in either ‘S’ or ‘Z’ twists. The thread is plied together to make bulkier and stronger thread. ‘S’ spun threads are ‘Z’ plied and vice versa.
The weaving process involves the use of a loom on which threads are laid down parallel to each other and held under tension. These threads, called the warp, run the entire length of the cloth being produced. Another thread is then interlaced between the threads of the warp in set patterns, alternating between travelling right and left through the warp. This interlacing thread, the weft, effectively creates the cloth. There are many types of weave, from simple to highly complex. Three of the more common weaves are shown below (Figure 1).
Plain or tabby weave is the simplest weave with the structure consisting of a one over and a one under pattern for the warp and weft. This produces a uniform surface on the front and the back of the cloth.
Twill weave is slightly more complex, involving a one over and two (or more) under structure in which each successive pass moves along one warp, creating a diagonal pattern. Variations of this pattern include chevron, herringbone and diamond twills.
Satin weave, although similar in structure to that of twill, does not have the characteristic diagonal appearance that typifies twill. This weave is smooth on one surface and dull on the other.
Woven textiles are often processed further before they are considered ready for use. Additional treatments may be aimed at improving appearance, texture, weight, flexibility or ease of care. The most commonly applied treatments include dyeing, bleaching, mercerising, weighting, moth proofing, sizing and glazing. The majority of textiles in a collection will have had some sort of finish applied to them.
As the original treatment of a textile is an inherent part of the item, it must be taken into account before any treatment is embarked upon. Otherwise, ill-considered conservation treatments may change the character of the cloth irreversibly.
Until the 19th century dyes were derived primarily from natural sources. Two of the best known natural dyes are indigo (from the indigo plant), and Tyrian purple (from molluscs).
Although some dyes have a natural affinity to fibres, most require the assistance of a mordant. The mordant, which is usually a metal salt, is applied to the fabric before dyeing to increase the attraction between the fibre and the dye. Mordants are also used to give the dyer a greater selection of colours. Madder dye for example, gives a rust red colour when used with an alum mordant and a brown colour with an iron mordant. Mordant dyes are used on fibres or fabrics of wool, silk, nylon and cellulose.
Although natural dyes are not generally considered to be fast to light, actual colour fastness varies greatly, depending on both the fibre type and the method of application.