The PISTACHIO repository contains spectral data from the PISTACHIO (Photonic Imaging Strategies For Technical Art History And Conservation) project, aimed at the validation and use of an FTIR hyperspectral imaging system for heritage science. Additional info can be found at http://pistachio.gla.ac.uk/ and in the EPJP paper by Botticelli et al., 2023 (doi: XXX). 
The database includes external reflection/ATR-FTIR spectral data for several pigments in oil, that can be used as research library. 

TYPE OF SAMPLE

Two different folders are deposited, depending on the type of sample analysed:

A. RECONSTRUCTION PANEL (folder name: 'Reconstruction_panel')

The panel reproduces D.Y. Cameron’s palette (known oil pigments or pigment mixtures on a boxwood panel). Several commercially available traditional oil paints were analysed: cobalt (CoB) and cerulean blue (CeB), vermillion (V), yellow ochre (YO) and ivory black (IB). Different white pigments were also included: titanium (TW), lead (LW) and zinc white (ZnW). Because the painting ‘Uplands in Lorne’ was found not to have a ground layer, the first row of squares in the panel is made of pure pigments on a rabbit skin glue size. The other rows represent mixtures of the pure pigments with a white, where the white pigment is in the first square of each row. To increase the level of complexity of the reconstruction, the last row has a mixture of lead and zinc white added to each pigment.  Titanium white is included as reference in the reconstruction, but it is not mixed with any pigment, as this type of white was not found in Cameron’s palette.

B. MOCK-UP SAMPLES (folder name: 'NaCl_windows')

Mock-up samples of the same pigments used in the recontruction panel were prepared on NaCl windows (diam. 25 mm) and analysed with the benchtop instrument in external reflection or ATR. 

TYPE OF ANALYSIS (Sept - Nov 2022)

Each main folder contains sub-folders depending on the type of analysis carried out on the sample:

- Benchtop micro-FTIR (sub-folder names: 'ATR' and 'External_reflection')

A Thermo Scientific Nicolet iN™ 10 MX IR imaging microscope, equipped with MCT/A detector. Spectra were collected in external reflection and ATR (Germanium tip) mode, at 4 cm^-1 resolution in the 4000–700 cm^-1 spectral range, with a beam aperture 200x200 micron^2. The collected spectra are the average of 64 scans, computed using Norton-Beer medium/strong apodization. The working distance is 20 mm from the object, with the angle between IR beam and detector being ca. 40°. Raw transmittance (%) data from ATR/external reflection measurements by micro-FTIR are provided as .csv and .spa files.

- PISTACHIO hyperspectral imager (sub-folder name: 'HS imager')

An in-house instrument built at Heriot-Watt University and developed at the University of Glasgow. Spectra were collected in external reflection, at 16 cm-1 resolution in the 1400–700 cm-1 spectral range, with 1 scan and 600 nm stage step size. The LWIR camera is positioned at a distance of approximately 85 mm from the object with the angle between incident and reflected light of approximately 20°. Raw Intensity data from the imager are provided as .txt files. They are also converted in .csv and .spa files.


Example of the notation adopted for file names:

EXAMPLE 1

'Cameron_reconstruction_CeB_LWZnW_refl_64s_200x200ap_point2.csv'
= .csv file from the recontruction panel, area painted with cerulean blue (CeB) mixed with lead (LW) and zinc (ZnW) white. The spectrum was aquired in external reflection (refl) after 64 scans (64s), with 200x200 micron^2 beam aperture, second point (point 2) analysed in the same area.

EXAMPLE 2

'Cameron_NaCl_IB + ZnW_ATR2_64s_point1.SPA'
= .SPA file from a mock-up sample (NaCl), area painted with ivory black (IB) mixed with zinc white (ZnW). For this analysis ATR-FTIR was used, collecting the average spectrum of 64 scans (64s), from the first point (point 1) analysed in the area.


EXAMPLE 3

'HSI_220920_ceb_v_cebznw_vznw_cerulean1.txt'
= .txt file from the area of the recontruction painted with cerulean blue (ceb), vermilion (v), cerulean blue with zinc white (cebznw), vermilion with zinc white (vznw), representative of the spectrum from point 1 in the area with cerulean blue (cerulean1). This spectrum describes the reflected intensity as a function of the wavenumbers.
.SPA and .CSV files derived from it are multiplied by -1 to be compared to absorbance spectra from other instruments.