Page 181 - Manual for Activities directed at the Underwater Cultural Heritage

in view of stabilizing their existing state while ensuring their accessibility to the present and future generations. Conservation actions can be divided chronologically into preventive conservation and curative conservation:
• Preventive conservation includes all indirect measures and actions aimed at avoiding and minimizing future deterioration or loss of materials or artefacts. It is carried out in situ within the context and surroundings of an object or a group of objects, or in the excavation laboratory. It should be undertaken regardless of the age and condition of the artefacts concerned.
• Curative conservation includes all actions directly applied to an object or group of objects and is aimed at arresting damaging processes and, when possible, stabilizing their condition against further deterioration.
Restoration is the continuation of the conservation process, when the latter is insufficient to re- discover the original surface of the artefact (without falsification), aiming at returning to the original appearance of an archaeological item as closely as possible and thereby providing a condition in which the artefact can be exhibited.
The conservation and restoration of underwater
cultural heritage call for comprehensive knowledge 180 of the environment in which a shipwreck or
© D.Nutley.Anchors of the Vernon on public display outside the Australian National Maritime Museum, Sydney, New South Wales.
Conservation costs for
individual objects can be very significant. Estimating the cost of conservation in a research plan must consider a range of factors including the size of the object and where the object is to be displayed.
The anchors of the Vernon represent an example of conservation by application
of a protective coating (both physical and chemical) for the
iron and anti-rot preservatives
for the timber.The cast iron of
the anchors is from 1839 and the timber stocks date to 1905.They have not been returned to an ‘as new condition’.
The decision to display the anchors outside and in an accessible environment to
visitors creates a challenge for
the ongoing preservation of the objects because of the artefacts’ exposure to the elements of wind, rain, sun, hail, humidity, sea spray as well as attack by vandals.
In the case of the Vernon, a display and mounting system was built
for the anchors which includes
an aluminium mesh on which
the anchors rest. Mesh rather
than solid metal allows water to drain away and aluminium was chosen because of its electrode potential relative to the iron in
the anchors. As the conservation treatment applied to the anchors (removal of the outer corrosion, blasting of the surface with copper slag, treatment with zinc epoxy paint) is less permanent than electrolytic techniques, the Vernon anchors are regularly inspected
for deterioration. Being on public displayasamemorialhasalso exposed the anchors to vandalism (2 rings were repaired and refitted after vandalism in 1992).
Conservation and site management