Every now and then in the field of building conservation, a new treatment or solution is developed which shows great potential to solve problems. The treatments are tested under laboratory conditions to understand how they interact with materialsl, their working parameters, and sometimes how and when they fail. The next stage is application in real-life situations. Nano-limes have been around for over fifteen years, but there are relatively few technical and practical studies to draw on. This month sees the publication a case-study in the use of nano-lime technology in the Journal of the Buildings Lime Forum which considers the potential of the treatment as an alternative to repointing.
Nano-limes are very small particles of calcium hydroxide suspended in an alcoholic medium, developed as a calcium-based consolidant and initially presented for the conservation of wall paintings and frescoes, and later extended to calcareous stones such as limestones. Nano-limes are consolidants, and should be approached and used following the same protocols, guidelines and level of caution established for stone consolidation. Lime-based consolidation using lime-water is a well-established conservation method for calcareous materials . However, there are a number of disadvantages to its use as it is labour-intensive requiring 100+ applications to achieve reasonable consolidation, the process typically introduces a significant amount of moisture to a deteriorating material, and lime deposition is typically limited to the outer few millimetres of the material precluding deep consolidation. Nano-limes presented an alternative to lime-watering, offering greater penetration with fewer applications, offering much higher lime loadings than water-based solutions with less potential for undesirable moisture-related side-effects.
Research into the application and use of nano-limes have focused on conservation of wall plaster and natural stones , but no published research to date on its suitability for conserving pointing mortars or external renders, with relatively few published case studies on its use in practice . The application of nano-limes is subject to the general principles and limitations of consolidating a porous historic building material whether it be stone, brick or mortar. The general principle of nano-lime is that the calcium hydroxide would precipitate within the pores of the mortar, and would then carbonate to calcium carbonate within fractures and the porous network of the mortar.
This month sees the publication of ‘Bartra Martello Tower: a case-study in the use of nano-lime technology’ in the Journal of the Buildings Lime Forum. This paper presents work using nano-limes as an alternative to the replacement of lime-based mortars and plasters. The key characteristics and properties of the original lime mortars and plasters, and treatment with nano-lime tested to establish its effectiveness in regaining cohesion in flaking and powdering lime mortars and plasters.