Application of three‐way mixed multivariate analysis of variance method to detect changes in chromatic coordinates (L*, a*, b*) in building granites

Abstract

In the present work we determined the chromatic coordinates (L*, a*, b*) for three building stones used in the heritage city of Ávila, Spain (World Granite Heritage City, 1988). The stones came from quarries and were subjected to 90 cycles of three types of accelerated ageing processes: (a) freezing/thawing together with cooling/heating (T1); (b) salt crystallisation (T2); and (c) freezing/thawing together with cooling/heating + salt crystallisation (T3). A three‐way mixed MANOVA (multivariate analysis of variance) was applied to the data obtained. Significant variations in the three chromatic coordinates (L*, a*, b*) were observed between the three types of accelerated artificial ageing processes compared to the data obtained from the quarry samples, with a tendency towards darkness (↓L*), redness (↑a*) and much less intensity towards yellowing (↑b*).