Cleaning marble, oolitic limestone and terracotta surfaces : a topographical assessment and comparison of the effects of conservation cleaning treatments on architectural materials
This project is an attempt to investigate the potential and applicability of White Light
Interferometry in surface studies in conservation and to establish a methodology to be used in
topographical studies of statuary and architectural materials. Surface texture is a key parameter
when dealing with works of art and is central in the assessment of cleaning treatments.
In addition to this, the development of laser cleaning as a conservation treatment has imposed
a need for the evaluation and assessment of other cleaning techniques. The use of more
traditional methods has relied so far on a visual assessment, unlike much of the research
applied to laser cleaning. A conscientious use of these cleaning methods requires their
assessment as well as the need for a comparison based on a common methodology.
In this study, the importance of surface texture in conservation is explored, followed by the
presentation of the principles of topographical studies. A topographical assessment of laser,
abrasive, steam, chemical (using hydrofluoric acid, ammonium carbonate and EDTA) and
water-based cleaning is presented, where topographical variations induced on marble, oolitic
limestone and architectural terracotta surfaces are assessed by means of light interferometry.
This research focuses on the topographical alterations occurred on both non-polluted and
polluted surfaces. Whereas the former is the basis of the investigation of the mechanisms of
interaction between cleaning treatments and the several materials tested, the latter will
contribute to the understanding of the topographical alterations occurred during cleaning
treatments. Based on this assessment, a comparison between the topographical effects induced
by these cleaning treatments is also presented.