Investigation of painting technique of Coptic icon by integrated analytical methods: imaging, spectroscopic and chemometric methods

Abstract

Essence of the cultural heritage is the preservation of the historic objects. The first action on the preventative issues is to know the technique used through implementation of different analytical methods. The studied object is a panel painting of a Coptic icon for Anstasy Al-Rumi the painter and it is documented with date back to the 16th century. Optical microscopy (OM), Raman microscopy (RM), scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) are good tools for forensic investigation of the multilayers of the painting; wood, canvas, paint colors (pigment, binder and varnish). Imaging methods have succeeded in identifying the wood and the canvas type, while spectroscopic methods manifested the elemental composition and characteristic bands of the paint colors, and principal component analysis reduced the variation in the colors retaining most of the information. The painting technique was tempera style involving Juniperus phoenicea wood, hemp canvas, animal glue, pine resin, lead white, gypsum, green earth, Prussian blue, yellow ochre, vermilion, carmine lake, carbon black and gold leaf in the icon painting. After investigation of the materials, the icon has not been referred to the 16th Century. Prussian blue was discovered at the start of the 18th century and Anstasy Al-Rumi the painter lived in the 19th century demonstrating that the icon may encounter previous intervention. There was a color loss as an indication of the aging process and chemical interactions with the environmental conditions.