shoes&pattens7

APPENDIX II

Conservation

Katharine Starling

See also Ganiaris et al. 1982; Starling 1984.

The naturę of excavated leather

Leather is composed mainly of the protein colla-gen arranged in fibrils which, in turn, make up the random, fibrous network that gives it its charac-teristic elastic ąualities. Tanning (see above, p. 46) retards the decay of collagen by inhibiting attack from many micro- and macro-organisms which may use it as a food source, and at the same time, to some degree, prevents Chemical decay. Leather also contains fats and oils from several sources. Some may be from the original skin, although most of these will have been removed during tanning; some may have been deliberately worked into the leather to increase flexibility; and others may have been accidentally absorbed during use - body fluids, for instance - or, morę rarely, during burial. The leather may also have been dyed.

Leather is not impervious to decay however, and will not survive unless the layers in which it is deposited exclude micro-organisms and the soil is not too acid or alkaline. The objects described in this volume were nearly al! found in waterlogged or thick wet clay deposits where little or no air was present. Some of the tannins and fats will have been washed out during burial, others may have seeped in. Salts and decay products from associated materials and from the surrounding soil may have stained the leather. Some decay may have occurred. The his tory of the leather before, as well as after, deposition is always a factor, as is the type of leather used.

Associated materials

Conservation is madę morę difficult by the pres-ence of other materials. These include metals, from buckles, strap-ends or decorative studs, and organie remains from stitching, textiles or the moss used for stiffening toes. Many pattens are madę partly from wood, and the surface of leather may be decorated with gilding or painting.

Condition

The condition of the leather on excavation varied enormously (see above, Table 21). Some pieces were remarkably good, flexible with little sign of degradation, whilst others were hard, brittle or delaminating badly. There were sometimes con-siderable concretions of soil and metal corrosion products, especially if there were iron fittings.

Before conservation

Leather can be stored before conservation either wet or frozen. Before 1982 the shoes were kept wet in a solution of a recommended fungicide, sodium orthophenyl phenate (SOPP), in tap water in a heat-sealed polythene bag with as little air as possible. From 1982 on they were usually frozen. They were still kept in a heat-sealed polythene bag, but with only a smali amount of water and no fungicide. A domestic chest freezer was used. The latter method has advantages in that it does not include the use of fungicide, which may be hazardous to humans and also interfere with analyses of dyes, fats, etc., and that it takes up considerably less space. Freezing does not appear to harm either leather or most associated materials, but if wood is present the object is stored wet, as its fragile celi structure may be damaged. If wet storage is only for a short period it may not be necessary to use a fungicide.

Choosing a conservation treatment

Excavated leather cannot easily be stored, handled or studied while it is wet. It is also vul-nerable to deterioration. If simply allowed to dry in air it shrinks, hardens, buckles and tends to look dark. This is because the strong surface tension of

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