In 2003, the conservators at the Textile Conservation Centre were charged
with carrying out first stage conservation, which involved cleaning the sail.
At the same time we were asked to assess the physical state of the fore topsail,
in relation to its handling, and to determine if the sailcloth was at immediate risk.
To be able to provide complete answers and ultimately advise on the most
appropriate approaches to conservation and display, it was essential to have
an understanding of the microstructure, chemistry and degradation mechanisms
of the constituent linen fibres. Further knowledge of the sail’s life also proved
critical – the mechanical stresses during its brief use and its exposure to the
marine environment, the damage it suffered during the battle, and the more sub-
tle deterioration over the subsequent two centuries of storage and occasional
display have all played a rôle in determining its current condition.
In the following paragraphs we will describe the chemical composition of
linen fibres and the microstructural hierarchy within them. We present the
results of our mechanical measurements, which helped establish the current
weakened condition of the cloth, and relate the reduced performance to the dis-
ruption of the fibres consequent upon ageing. This, in turn, leads into a discus-
sion on the mechanisms of cellulose degradation (which apply equally to wood
and cotton cellulose). As we will see, one expected outcome of oxidative deteri-
oration is the generation of carboxylic acids, with potentially deleterious con-
sequences for the cellulose polymer chains. Measuring the acidity of historic
linen fibres is therefore crucial and, as outlined at the end of this case study,
allowed us to make some recommendations concerning the longer-term preser-
vation of the sail.
3.1 The Chemical Composition and Microstructure of Linen
Linen is derived from certain varieties of flax (Linum usitatissimum); other
varieties of the species are cultivated for linseed for the production of oil. The
flax fibres make up 15% by volume of the plant stem. They are found in the
bast, a fibrous layer next to the woody interior, acting as structural braces. To
isolate the fibres and remove the non-fibrous and woody tissue, traditionally
linen straw is retted (wetted to permit biological attack on the inter-fibre glue),
scutched (mechanically stripped) and hackled (combed), leaving yellow/brown
ligno-cellulosic fibres. These can be bleached white for fine textiles, generally
after spinning and weaving. The fibres are cellular in nature, being composed
predominantly of cellulosic cell walls around a hollow lumen. Bundles of these
individual cells (known as ultimates) are then cemented together by the middle
lamella. The cell walls are largely made from polysaccharides (80%), in
addition to a smaller proportion of lignin (2%), proteins, pigments, waxes and
minerals. The polysaccharide component is primarily cellulose (in the form
-cellulose or cellulose I) (64%), along with hemicelluloses (17%) and pectins
60 Chapter 4