Nano-Lime for Consolidation of Plaster and Stone: Fid-Bau Portal

Nano-Lime for Consolidation of Plaster and Stone

D'Armada, Paul / Hirst, Elizabeth

Stone consolidants should, ideally, be physically and chemically compatible with the materials requiring consolidation. The theoretical principle of getting calcium hydroxide into a decayed calcareous substrate, and allowing it to carbonate, has long been understood and was the reason why limewatering (a method refined by Professor Robert Baker in the 1970s and 1980s) was used on several important projects, including the carvings to the west front of Wells Cathedral. Nano-lime has been developed as a method of consolidating limestone and lime plasters because it offers theoretical advantages over traditional materials such as limewater and lime grouts. Preliminary investigations to determine its performance characteristics prior to its specification and subsequent use on medieval wall paintings were undertaken by Hirst Conservation in 2010. Although these tests were limited to only a few materials, results were encouraging and highlighted some of the product's advantages and disadvantages. The results clearly show that rates of penetration vary significantly according to the type of material, its porosity and other factors. Nano-lime dispersed in alcohol can work well as a consolidant if used in the correct manner, allowing time for maximum penetration, precipitation and carbonation of the nano-lime. This may take days or even weeks for each saturation.