Comparison Between Colorimetry and Sensory Panel in Studying Similarity Between Roman and Integration Bricks, Assisted by Multivariate Data Treatment

ABSTRACT

The restoration of the Roman building of the third-fourth century CE called Minerva Medica, in Rome, highlighted a problem concerning the choice of the color of the bricks for integration. Current conservation practice in Italy favours a restoration that as much as possible is consistent with the original but leaves some visible differences to a careful observer. Color measurement is usually performed using portable spectrocolorimeters that provide the reflectance spectrum and also colorimetric parameters such as L* a* b*, h* L* C*, RGB, etc. In other sectors, such as for olive oils, for wines, and also for the colors of commercial products, sensory panels are used to provide results of difference/similarity and are known to be similar to observations made by consumers. In this study, data from a top quality spectrocolorimeter and from a sensory panel are compared. Twenty non-professional people were involved in the comparison between seven restoration bricks and three ancient Roman bricks from the studied site. Observations took place in a room with controlled lighting, and each observer filled out a sensory card using about 2000 known comparison colors. Comparison of the results was carried out with graphic methods and by means of cluster analysis. The results show that the sensory panel could be a useful alternative to colorimetry, while cluster analysis allowed a significant response to questions posed by conservation professionals, and was confirmed by other graphic-statistical methods.

KEYWORDS:

• Ancient Roman building
• restoration bricks
• colorimetry
• sensory panel
• cluster analysis
• statistical data processing

Acknowledgements

We would like to thank the Soprintendenza Speciale per i Beni Archologici di Roma, in particular Dr Maria Rosaria Barbera and Arch. Marina Magnani for furnishing the materials and for useful information.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 http://tdselz.ru/category_small_sub/view/6/ (in Russian)