Identification of pigments in artworks by inverse tangent derivative of spectrum and a new filtering method

F Fazlali,S Gorji Kandi

doi:10.1186/s40494-020-00438-4

Abstract

Employing an economical and non-destructive method for identifying pigments utilized in artworks is a significant aspect for preserving their antiquity value. One of the non-destructive methods for this purpose is spectrophotometry, which is based on the selected absorption of light. Mathematical descriptive methods such as derivatives of the reflectance spectrum, the Kubelka–Munk function and logarithm have been employed for the characterization of the peak features corresponding to the spectrophotometric data. In the present study, the mentioned mathematical descriptive methods were investigated with the aim to characterize the constituents of an Iranian artwork but were not efficient for the samples. Therefore, inverse tangent derivative equation was developed on spectral data for the first time, providing considerable details in the profile of reflectance curves. In the next part, to have a simpler and more practical method it was suggested to use filters made up of pure pigments. By using these filters and placing them on the samples, imaging was done. Then, images of samples with and without filter were evaluated and pure pigments were distinguished. The mentioned methods were also used to identify pigments in a modern Iranian painting specimen. The results confirmed these methods with reliable answers indicating that physical methods (alongside chemical methods) can also be effective in determining the types of pigments.

Highlights

There are several complementary analytical techniques to provide an understanding of the composition of the materials in artworks that can be classified into destructive and non-destructive
Some spectrophotometers such as Fiber Optic Reflectance Spectroscopy (FORS) methodology provides the possibility to collect reflectance spectra from very small areas of the surface of paintings. This technique is portable, lightweight, compact, low-cost, high speed, and easy to use [15, 16]. This identification method is very useful for the characterization of pure pigment in artworks [11]
The samples were separated based on hue, and mathematical descriptions were

Summary

Introduction

There are several complementary analytical techniques to provide an understanding of the composition of the materials in artworks that can be classified into destructive and non-destructive. While absorption of light is a relatively straightforward phenomenon, diffusion is more complex since it depends on the pigment specifications such as particle size, angle of impact, suspending medium, and difference in refractive index of pigment [12,13,14] Some spectrophotometers such as FORS methodology provides the possibility to collect reflectance spectra from very small areas of the surface of paintings. This technique is portable, lightweight, compact, low-cost, high speed, and easy to use [15, 16]. This identification method is very useful for the characterization of pure pigment in artworks [11]

Objectives

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Results

Conclusion