display, resting at a shallow angle on a support platform. These recommenda-
tions were necessary in light of the reduced strength and, in particular, facile
deformation consequent upon the aged condition of the sailcloth and the
degraded state of the constituent fibres.
3.3 Degradation of Cellulosic Fibres
Deterioration of each of the fibres’ various components will affect the mechan-
ical performance, but to different extents and through different mechanisms.
Breakdown of the intercellular glue will obviously facilitate slippage of the
ultimates, and this is often a particular problem for archaeological linen. Here
though, we have chosen to focus mainly on the deterioration of the structural
cellulose filler, which may be the more pertinent to the weakened condition
of the Victorysailcloth.
Cellulosic materials are susceptible to a range of degradation processes,
including those associated with chemical (e.g.acid attack, photolysis, micro-
bial and fungal metabolism) and thermal degradation. In general, the deterio-
ration of the material is due to oxidative processes or hydrolysis, leading to both
scission and cross-linking of the cellulose polymer. In any event, the general
result is a polymer assembly with a lowered degree of polymerisation, increased
crystallinity due to aggregation of some of the smaller chains, and the devel-
opment of some network character, and hence weakening and embrittlement.
Humidity and Heat. Moisture is crucial to the normal behaviour of cellulosic
fibres. Under moderate conditions (relative humidity 45–65%) water is read-
ily absorbed through the network of pores running through a fibre cell, it coats
cellulose crystallites and acts as a plasticiser of the amorphous regions, dis-
rupting inter-chain hydrogen bonds. Without this bound water the fibre would
be permanently brittle, with an effective glass transition point way aboveroom
temperature.
Humidity extremes, however, cause problems. High humidities lead to swell-
ing,which may be disruptive, particularly for aged fibres. The opening of the
polymer structure invites ingress by damaging pollutants and salts. The con-
ditions also favour mould growth and microbiological breakdown.
Soaking in sea spray, of particular relevance to the Victorysail, will have led
to increased swelling of the fibres, due to the penetration of hydrated sodium
and chloride ions. On drying, swollen fibres will suffer dimensional changes,
which in turn can lead to the distortion of the fabric. For the brine-laden sail-
cloth, further disruption of the linen would have ensued as the salt crys-
tallised within the fibres.
Desiccation, under drier conditions (RH30%), will lead to increased cross-
linking of the chains in the amorphous zones through secondary bonding, and
brittleness. The overt results are shrinkage and loss of flexibility. As the
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