1 INTRODUCTION

So rarely are historic textiles retrieved from long-term storage in the marine environment that little is known about the degradation processes they have undergone, the consequent chemical and physical structure of the degraded materials, and the appropriate methods for their conservation. The fiber content of some marine textiles has been identified, for example, the wool and linen from the Mary Rose has been described by Ryder and Gabra-Sanders (1985). Their methods were limited to microscopy and scanning electron microscopy; although the fibers were identified, their chemical macromolecular physical structure was not characterized. The difficulty of identifying certain historic and archaeological textile materials of any provenance is noted by many authors (King 1978; Schaffer 1981; Goodway 1987). Techniques that characterize archaeological textile materials have been undertaken in few cases, none with examples from the marine environment (Jakes and Sibley 1989; Jakes and Angel 1989).

So little is known about the degradation of textiles in marine environments that conservation of the few examples that have been found has taken an experimental approach—sometimes successful, sometimes unsuccessful. Somewhat more research has been conducted on waterlogged wood. Such treatments may suggest possible routes for treatment of textiles (e.g., Rosenquist 1975; McCawley 1977; Grattan 1989), but the difference in bulk between the two will dictate some differences in handling methods. For example, wood artifacts contain internally adsorbed water, which is not removed by normal sublimation of ice in freeze drying (Rosenquist 1975). As a result, differential drying and shrinkage of the piece occur. Textiles, on the other hand, have less bulk and a large surface area; ice within the textiles is readily accessible to sublimation through freeze drying. In addition, treatments useful for drying waterlogged wood may not be directly translatable to textiles due to the effects of processing, dyeing, and other treatments, which increase the complexity of textiles and complicate the prescription of the appropriate handling methods.

Pearson (1987) describes work done with archaeological marine textiles in the categories of drying from water, from other liquids, with consolidants, with bulking agents, with lubricants, and by sublimation. Mayhew's review (1990) compiles some of the literature on waterlogged textile materials. Drying from water is the most desirable and least intrusive method if no fiber shrinkage or embrittlement occur. Drying from other liquids can reduce fiber collapse on drying but can also remove components of the textile such as dyes, pigments, or fats and oils. Bengtsson (1975) dried sails and ropes from the Wasa by extracting the water with alcohol followed by xylene. Xylene was used to allow fabric drying without shrinkage, but the resulting textiles were brittle and fragile.

Drying with consolidants such as polyvinyl acetate and bulking agents such as polyethylene glycol has been reported. Grosso (1975) cleaned historic textiles with soap, then mounted the fragments on glass using a polyvinyl alcohol solution. Morris and Seifert (1978) used a polyethylene glycol consolidant prior to vacuum freeze drying of a shot bag from the Defence. Leather objects have been successfully treated by freeze drying them with a glycerol lubricant (David 1981; Ganiaris et al. 1982), and Pearson (1987) suggests the adoption of this method for textiles.

Norton (1990) reports on conservation treatments for archaeological and historic objects made from plant materials. She states that the use of water alone is sufficient to cause damage in materials. Polyethylene glycol lubrication can discolor with time. Consolidants can darken and gloss with time, and they can stiffen the fabric. Some consolidants can contribute to artifact degradation.

Nonalteration of the basic fabric is the goal of the conservator; some care should be given in choice of treatments since so little is known about the long-term effects of those treatments. Pearson (1987) notes one personal communication that states the effectiveness of slow drying from the frozen state in the drying of archaeological textiles.

Peacock (1990) addresses the need for basic research on the use of vacuum freeze drying with archaeological textiles. While vacuum freeze drying has been employed in isolated cases, she cites many problems with these studies, including the fact that despite the use of a variety of pretreatments, no research has been reported concerning the compatibility of these treatments with the fibers and fabrics treated.

Conservators agree that treatments traditionally employed and generally accepted may not be as successful as they first appeared. A recent symposium of textile conservators addressed these issues (Harpers Ferry Regional Textile Group 1986). Even the longstanding procedure of needle stitching support fabrics to fragile textiles was questioned at this symposium.

Since the opportunity existed to work with a large number of waterlogged textiles of known provenance, a research plan was developed that contributes to the knowledge of waterlogged historic textiles and their conservation. The quantity of waterlogged textiles available allowed some to be used for experimentation. In this paper, a salvage operation is described in which the textiles were frozen to halt degradation. The subsequent evaluation of appropriate drying methods for these waterlogged textiles is reported.