Stone Conservation: An Overview of Current Research (2010)

Stone Decay 7ing the difficult challenge of long-term evaluation of stone treatments(Simon and Lind 1999; Favaro et al. 2006; Favaro et al. 2007).The development and application of the drilling resistance measurementsystem (DRMS), also known as the drilling force measurementsystem (DFMS), has provided an extremely useful and minimally destructivemethod for evaluating the condition of stone and the performanceof treatments for stone (Lotzmann and Sasse 1999; Leroux et al. 2000;Delgado Rodrigues, Ferreira Pinto, and Rodrigues da Costa 2002;Pamplona et al. 2008). The system uses a portable drill and ceramic drillbit with a sensor to measure the force needed to advance the drill bit agiven distance. In principle, the DFMS can determine depth of deteriorationand the penetration depth of consolidants, in situ, with a minimumof destruction (a 3 mm hole).Ground-penetrating radar is increasingly used in archaeologicalprospecting, and it is natural that its use should be extended to historicbuildings (Finzi, Massa, and Morero 1992). It has seen wider applicationrecently by a number of researchers (Binda et al. 2003; Binda, Lualdi, andSaisi 2007; Huneau et al. 2008; Palieraki et al. 2008). The method is usefulin detecting flaws, voids, moisture, metal straps, and the thickness ofstone masonry.Infrared thermography has been used by a wide range ofresearchers (Moropoulou, Avdelidis, and Theoulakis 2003; Grinzato et al.2004; Tavukçuoglu et al. 2005) to study moisture in stone. To provideuseful results, a thermal contrast, such as solar heating or deliberate heatingby infrared lamps, is often needed to identify the different surfacetemperatures related to differences in moisture content. This method isknown as photothermal radiometry and has been developed to detectdelaminations and voids (Madrid, Coffman, and Ginell 1993; Candoré etal. 2008). Most building materials have significant thermal inertia, andpractitioners using thermography on a casual basis will not necessarilyfind useful temperature contrasts.One interesting way to look into a stone’s subsurface for smallsurface detachments is to use the sensitivity of laser holography interferometryin combination with varying sound vibrations from a loudspeakerto map detached segments of wall paintings or stone surfaces(Castellini et al. 2003; Gulker, Hinsch, and El Jarad 2004; Keene andChiang 2009).A range of field evaluation methods has proven useful for quantifyingwater uptake and surface coherence, including the sponge andScotch tape tests (Urzï and De Leo 2001; Vergès-Belmin and Laboure2007; Vandevoorde et al. 2009).Laboratory-Based MethodsSo far, we have considered minimally destructive techniques. It is,of course, possible in some instances to remove samples for analysis inthe laboratory. These will often consist of core samples, which are slicedparallel to the original surface. The slices may be examined using the normaltechniques for characterizing stone, such as polarized light microscopy,scanning electron microscopy combined with energy- dispersive