During the time since it sank in 1545, Henry VIII flagship, the Mary Rose, layers of silt have protected the vessel’s hull and contents. The hull, which is now being actively conserved within a dry dock in Portsmouth’s Historic Dockyard, is the world’s largest archaeological conservation project.
The ancient oak hull is housed beneath a double-skinned, thermally insulated protective roof. It is being sprayed continuously with an aqueous solution of polyethylene glycol (PEG), which is penetrating deep into the delicate cell walls of the timber. By replacing the water in the cells, the PEG will minimise distortion of the hull when it is eventually dried out.
The project would not be possible without sophisticated remote monitoring and control. A Honeywell Excel 5000 management system monitors and controls some 250 parameters and integrates with an Excel Building Supervisor building management system. Its duties include monitoring spray pumps, filter pressure, tank level and many other variables and also regulate the heating system within the ship hall and ventilation the glass-fronted viewing gallery.
A second system is installed in the exhibition building and is much smaller. This provides ambient heating and air conditioning as well as precise temperature and humidity control within numerous sealed glass-fronted display cabinets, in which some 1000 treasures are on public display.
‘The hull treatment process must be continuous to prevent it drying out, so we are grateful that Honeywell’s Response Centre in Bracknell monitors around the clock,’ explained conservation scientist Dr Mark Jones, Head of Collections with The Mary Rose Trust. ‘At the first sign of a problem, the Response Centre will alert our engineers so we can take immediate action.’
Glenn McConnachie, the Trust’s Conservation Manager, added: ‘The critical alarms are associated with the hull conservation process and indicate a spray system failure. Specifically, the critical alarms are low level in the sump tank, into which the spray solution drains for re-circulation, and high and low pressures within the spray system. These pressure abnormalities would most likely be due to, respectively, a system blockage or a blow-out in the spray system.’
The Mary Rose Trust also has a freeze drier unit, operating at -30oC and low pressure, that is used to preserve small archaeological treasures. This exacting conservation process is ensured through links to the Honeywell Excel 5000 system, which extends further critical alarms to the Response Centre for 24-hour monitoring, which is provided by Honeywell free of charge.
Editor’s note: Henry VIII’s flag-ship the Mary Rose was built between 1509 and 1511 in Portsmouth and listed as 400 tons. Rebuilt in 1536, the vessel was uprated to 700 tons but sank accidentally in 1545, just 2km from the entrance to Portsmouth Harbour, while preparing to engage a French invasion fleet.
The Mary Rose Trust, a registered charity with HRH Prince Charles as President, was formed in 1979 to carry out excavation of the ship and its contents, with the eventual aim of revering and preserving the ship for permanent display.
Over 600 volunteer divers, and many more on shore, helped with the work. Many artefacts and 3,000 timbers were recorded and brought ashore, leaving the hull to be raised in 1982.