Vol. 500 No. 3
82 Mr. Gormley asked the Minister for Finance if she will report on the progress of cleaning the facade of the National Museum and the National Library; the methods used to clean these surfaces; and if he will make a statement on the matter. [2770/99]
The facade of the National Museum of Ireland building in Kildare Street had seriously deteriorated within 30 years of its construction date which is given as between 1885 and 1891. The stone used was face-bedded rather than end- bedded and the masons involved used the softer rather than the harder face as a front.
The building maintenance service of the Office of Public Works, which has the expertise available to undertake specialist projects on prestigious buildings, undertook the complete restoration of the exterior stonework of the National Museum building. The project, which commenced in 1995, is the largest of its kind in Europe. The work involves not merely the cleaning, but the reconstruction of large areas of the carved stone mouldings and details, which have been corroded by pollution over the years.
The stone facework is cut back or keyed, using a grinder, hammer and bolster. Then layer after layer of specially formulated mortar is built up before being moulded into the desired shape. For larger pieces, templates are made up on site and transferred to be made into moulds which are then cast off-site.
The cleaning of the facade involves the use of sandstone cleaner chemical 100 which is used for the removal of dirt and grime from sandstone, unpolished granite, brick and terracotta. It will remove iron stains from masonry and contains agents to prevent iron stain formation on the stone face. Calcium carbonate which contains fine carboniferous limestone granules is also used. The product is crushed and screened several times, then air classified to produce a material of high purity with a controlled level of fines. It is dried to give a very low moisture content. The cleaning of the facade also involves the use of oligomer siloxane solution with additives for water repelling impregnation of cementitious building materials. This product was especially developed as a water repelling treatment for natural stone.
The cleaning products and the cleaning method conforms to BS 6270. In effect, the whole facade of the National Museum building is being restored or cast anew under this ambitious project. These works are due to be completed in 2001 at which stage, a similar project for the National Library building will be undertaken.
