The Conservation Project

 
EXPO 2005 Japan poster

At the end of January 2005 six plaster copies of High Crosses of Ireland, owned by the National Museum of Ireland, were installed in the Irish Pavilion at the World Expo site in Aiichi, Japan. The casts are full size replicas in plaster, the tallest standing at over 6.5 metres.

Made in the 1890’s these casts were made by taking moulds directly from the original stone crosses.

Treatment

In order to exhibit these pieces it was necessary to follow a five step conservation programme for the plaster. This work was done in conjunction with the Office of Public Works (OPW) team responsible for the structural fortification of these casts to enable them to travel and be exhibited in an earthquake zone in Japan.

Cleaning

All plaster elements were “cleaned” with compressed air. This method of dry cleaning allowed for the removal of all the loose flaking paint while avoiding the need for aqueous treatment prior to consolidation, which due to the fragile nature of these plaster casts would not have been desirable. It also enabled the conservators, Lorna Barnes and Jason Ellis, to test the “soundness” of the plaster and remove and reaffix and loose areas.

Repairing, unpacking and displaying the crosses

Consolidation

This treatment was to consolidate the old flaky plaster throughout its thickness and to consolidate the surface of the casts. Many consolidants, using solvents, could not be considered due to the scale of the project and health and safety issues.

Loss compensation and filling

The edges of all the plaster elements, called “joins”, had suffered particularly over time and it was necessary to build up these areas again, complete with detail, so that the crosses could be re-erected. All fills and losses were made with reference to photographs of the original stone crosses and discussion with Raighnall O’Floinn, Head of Collections at the NMI. The intention was to remain “true” to the plaster casts which were made in the 1890’s. Some casts required only a little additional detail, notably the Ahenny Crosses, while Muiredach’s Cross and The Tall Cross, from Monasterboice, required considerable loss compensation in plaster.

As the old paint coat applied during the last century could not be easily removed from the plaster it was necessary to “fill” all paint losses  to provide a smooth surface for re -painting. In addition numerous nicks and dents were also filled prior to re-painting.

Joins

The areas where the casts joined had suffered particularly when the crosses were dismantled. In order for the casts to “join” it was necessary to make up quite large areas in Plaster. These areas were left slightly shy of a full join, which had to be filled in as a final step in Japan.

Structural Support

High Cross replica

As the casts were travelling to an earthquake zone they had to be further braced inside to withstand vibration. The OPW team, headed by Ben Faye, engineered a steel “totem” pole onto which all the pieces of each cross could be slotted. This system enabled every piece of the cross to be fixed to the steel infrastructure while removing the need for these fragile elements to rest on each other. The team also fortified the casts from inside with new plaster and wooden struts. In addition the team also fixed straps into each element on the inside to enable the pieces to be hoisted by a crane into position while minimising the need to handle the delicate pieces.

Painting

All the crosses were painted in the same way, with varying shades, to replicate the effect of the original stone crosses. The crosses once erected give the illusion of being single pieces rather than four or five elements joined together.

 
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