## 4 Discussion and Future Directions  
The politicing approach to sampling soluble salts appears to work well, at least in the situation investigated. Clearly, many more stone types and other substrates and soluble salt ions need testing. This is planned in the GoGreen project [34]. The application of wet poultices to some stone objects will not be possible, and also further work is required to ensure the poultices protect the surfaces from salt damage when drying. The salt ions were apparently removed from a greater depth than the liquid water had penetrated from the poultice. This could be explained by water vapour penetrating beyond the water front. This would cause the salts to deliquesce, provided the RH was sufficiently high. The salt solution could then be drawn along with the liquid water as the poultice dried and drew the water back into it. Combining measurements from an Hf Sensor M350 microwave moisture meter and Protimeter Surveymaster gives a reasonable measure of the conductivity of liquid salt solutions in calcite columns. It seems likely that this approach will be extendable to other materials. Separate calibrations are required for each subset of materials with the microwave meter, and software is available to undertake these. The method appears to be feasible, although there is a slight mismatch between the microwave and protimeter information depths. If dielectric meters with deeper information depths can be sourced, they can be combined with different microwave heads to undertake measurements further from the object surface. Heads are available with information depths of 3, 7, 11, 30, and 80 cm from the Hf Sensor. Additionally, the sensitivity of the methods to different depths has not been investigated. We plan to continue with further experiments with the calcite cylinder to investigate this aspect. The combined method can generate maps of object surfaces, which could direct invasive (drilled) sampling between groups of objects and within single objects. The reflectance FTIR successfully identified the mixed acetate salt found on the cuneiform tablets. The rapid analytical time and limited manipulation of samples allowed many more analyses than previous methods, sample removal and XRD or FTIR. This was important when faced with a large number of instances and gave confidence to the results obtained. A clear segregation was determined using the chloride and sulphate salt contents of a group of cuneiform tablets exposed to high RH and acetic acid concentrations. Within the analysed group, tablets with no visible salt efflorescence were clearly distinguished from those that underwent heavy reaction. Salt analyses appear to be predictive as to whether a particular tablet will react or not. It is possible the salts present in the tablets deliquesce and the acetic acid deposition into these solutions is increased compared to dry deposition. The observation of reaction only after high RH (the tablets had been previously exposed to summer RHs peaking between 71 and 74% for the past 20 years) does seem different from [PERSON]'s observation that the salt grows in conditions of 40-60% RH [35]. Figure 14: Map of muscovite clay content analysed with NIR across break surface of stone fragment from Theftord. Some cuneiform tablets were fired, and the poultice method could be applicable for determining the salts present, although further work on the information depth from poultice would be required. The ATR-FTIR successfully identified the removed clay samples. The actual analytical area is less than 1 mm\({}^{2}\) and the information depth for the diamond crystal used is likely to be in the order of 1 \(\upmu\)m from the Harrick equation at 3300 cm\({}^{-1}\) and using 1.551-1.613 as the refractive index of muscovite clay [36; 37; 38; 39]. This could lead to issues with non-homogeneous samples, but multiple analyses should be able to quantify this and still retain significant time savings compared to XRD. The in situ analyses worked well with both direct-reflection FTIR and NIR.