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Proceedings Paper

Infrared detection of moist areas in monumental buildings based on thermal inertia analysis
Author(s): Ermanno G. Grinzato; Andrea Mazzoldi
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Paper Abstract

This paper presents a technique to detect the moisture conditions of walls supporting frescoes in order to detach its in case and to understand causes of the surface wetting. An important feature of the testing procedure is to be nondestructive and appropriate to analyze large surfaces as it is based on thermographic image processing. The goal is to classify the wall surface on the basis of its moisture condition. We choose the thermal inertia as the most suitable parameter for this purpose, because the heat capacity of a porous body increases to a great extent by varying its water content. The test works modifying the wall inner thermal conditions and detecting temperature variations of the fresco, in time and space domain. For this purpose a convective thermal flux is uniformly applied to the surface while an infrared camera views it. In such a way temperature gradients appear, whose maximum directional variation curves are used to segment the surface and the mean temperature time difference is used to label each area. The key point of the proposed procedure is the freedom from the knowledge of the wall composition and its thermal and hydrologic dynamic status, depending on weather history. Other topics as the environmental radiometric reflection and emission, the 'Narcissus effect' in thermograms mosaic composition and the perspective distortions are considered. Experimental results on a XVI century church at Padua (Italy) are presented.

Paper Details

Date Published: 1 March 1991
PDF: 8 pages
Proc. SPIE 1467, Thermosense XIII, (1 March 1991); doi: 10.1117/12.46425
Show Author Affiliations
Ermanno G. Grinzato, ITEF/CNR (Italy)
Andrea Mazzoldi, ISDGM/CNR (Italy)

Published in SPIE Proceedings Vol. 1467:
Thermosense XIII
George S. Baird, Editor(s)

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