Micro-Raman Spectroscopy,X-ray Fluorescence,and X-ray Diffraction Analysis of Materials,Stratigraphy,Hidden Inscriptions,and Artistic Techniques in Portrait of Farrokh Gaffari

Abstract

This study employs an integrated, multi-technique, minimally microinvasive investigation of the material composition, stratigraphy, and technique of the Portrait of Farrokh Gaffari, which was created in 1959 by Qollar-Aqasi, an artist of the Iranian Coffeehouse Painting workshop, thereby closing the element → phase → molecule evidence chain by combining whole-field macroscopic X-ray fluorescence analysis (MA-XRF) with X-ray diffraction (XRD) and micro-Raman, complemented by cross-section microscopy and fiber analysis. MA-XRF resolves two subsurface narratives: Continuous Sr and Ba-K line patterns that expose hidden Persian lettering on a reused shop-sign support (blue ground with white lettering), and an Fe-mapped pentimento masked by Fe-poor overpaint, documenting a localized compositional revision. Mapping and section analysis reveal a zinc-rich gray priming beneath the paint and multi-campaign varnishes. Using Bruker Gamma Filter technology, effective separation of substrate-derived and surface zinc signals was achieved, thereby improving the accuracy of spectral targeting. Raman identifies lithol red (PR49, likely PR49:2) as the principal red and Prussian blue (PB) as the main blue. Ultramarine occurs as deep-blue accents. XRD identifies lithopone (BaSO₄+ZnS), zinc oxide (ZnO), and lead chromate (PbCrO₄), rationalizing why the red is XRD-silent while whites/yellows are phase-visible. Together, these data resolve a compact, high-saturation palette logic: mixture-greens from PbCrO₄ + PB, lithopone-moderated whites and reds, and area-specific combinations (e.g., canopy: PbCrO₄ + PB + iron oxide + lithopone; fountains and flowing water: PB + lithopone, flowerbeds/red blossoms: lithol Red (PR49) + carbon black). Fiber microscopy identifies a cotton support assembled from two panels with orthogonal warp orientations. Furthermore, it is worth noting that this painting was executed on a repurposed blue-background-with-white-lettering advertising sign, which is a substrate choice that not only aligns closely with the pragmatic “local material adoption” principle of the Coffeehouse Painting workshop but also echoes their typical painting-on-a-sign practice, with the original sign’s material composition specified as follows: the blue ground comprises CaCO₃, BaSO₄, and PB, while the white lettering is formulated with BaSO₄.

Graphical abstract

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