Week 6 of 12
Module 4: Deterioration Mechanisms; Methods of Survey & Analysis
Marisa Laurenzi Tabasso (see Day 20 (11.05.2011)) returned today to discuss 'Micro-Destructive Diagnostic Criteria & Techniques' and 'Sampling Methodology and Techniques'. Diagnosis of deterioration should form the basis and reference point to plan and design the conservation intervention; 'we cannot conserve what we don't know'. As Marisa identified, far too often it is the conservation decision that comes first, and then the diagnosis of deterioration.
In an ideal situation a conservation scientist should be employed from the start of any conservation project to be involved in the sampling, analysis and interpretation. A scientist unfamiliar in the field of conservation may provide highly accurate results, but will not have the same skills or insights for making the interpretations, which are arguably the most important part of the analysis.
We had a detailed discussion on the types of analysis methods available including the following; optical microscopy, scanning electron microscopy (SEM), x-ray fluorescence (XRF), x-ray diffraction (XRD), ionic chromatography, Fourier transform infra-red spectrometry (FTIR), Raman spectroscopy, UV-Vis spectrophotometry, mass spectrometry (e.g. gas chromatography), thermal analysis (e.g. thermogravimetry), mercury injection porosimetry (MIP) and ultrasonic measurements/tomography. Many of the above techniques I have used either in my work at the Scottish Lime Centre Trust or previously, however I have not come across MIP analysis before and I am interested to learn more. The technique I currently use in my work allows me to identify the percentage of open porosity in a stone, but does not provide an idea of the pore shapes, sizes and connectivity which this method allows. It is a highly sophisticated technique and could provide some very interesting information about the capillarity and movement of moisture within different types of stone or mortar.
An interesting point to note is that the majority of techniques applied for analysing stone were originally developed in other industries. This is worth remembering when it comes to borrowing or hiring equipment; John Fidler in one of his lectures mentioned it is sometimes possible to invite other organisations onto your site to demonstrate or test their equipment and therefore find a shared benefit in analysis investigations.
This afternoon we returned to our work site, the Non-Catholic Cemetery to begin to diagnose the reasons for the deterioration that is present on the tombs on which we're working and to identify any forms of analysis or further investigation we wish to carry out. Two of the things we have identified that we wish to learn more about are available techniques for consolidation of areas of stone that are detaching (particularly areas of carved lettering) and an investigation into the biological growth on the stone and whether it is having a damaging or protective effect. We will be learning about stone consolidation in week 9 of the course and bio-deterioration both at the end of this week and in week 10, which I hope will lead us towards a better understanding of these two topics for making our decisions in regard to our project.