Conservation of Ancient Timbers from the Sea 301
compounds, which can be treated differently: particles of iron(II) sulfide pre-
sent in the cell lumen and organosulfur compounds firmly bound in the lignin-
rich parts (middle lamella) of the wood cell wall. The sulfides are oxidised in
humid conditions and are probably the source of most of the acid present. In the
timbers of the Mary Rose, sulfides are abundant, but there is little sulfate, prob-
ably because of the constant spraying during the active conservation treatment.
Monitoring the state of archaeological wood and its environment during
conservation is an important aspect for their long-term preservation. Changes
of environment during excavation, treatment and storage can result in the initi-
ation of chemical and biological processes that may ultimately destroy the
object. The acidification of archaeological wood once excavated is a problem of
immediate concern. It is therefore important to monitor the chemical changes
and microbial activity in the timbers during conservation and display.
5.2 Microbial Activity
Sulfur-metabolising organisms have been monitored within the timbers of
the Mary Roseby extraction and analysis of bacterial ribosomal RNA. The
Figure 18Normalised sulfur K-edge XANES spectra (Daresbury) from sections of oak core
from surface (0 mm) and inwards taken from untreated Mary Rose timber