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

Abstract

[EN]In the present work we determined the chromatic coordinates (L*, a*, b*) for three building stones used in the heritage city of ´Avila, Spain (World GraniteHeritage City, 1988). The stones came from quarries and were subjected to90 cycles of three types of accelerated ageing processes: (a) freezing/thawingtogether 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 appliedto the data obtained. Significant variations in the three chromatic coordinates(L*, a*, b*) were observed between the three types of accelerated artificial age-ing processes compared to the data obtained from the quarry samples, with atendency towards darkness (#L*), redness ("a*) and much less intensitytowards yellowing ("b*).