Notes to the User
The paintings catalogued here belong to the Pissarro family, Camille Pissarro and his two sons Lucien Pissarro and Georges Manzana Pissarro, and are housed at the Indianapolis Museum of Art. This catalogue consists of a featured essay which discusses the materials and painting techniques of the artists and how they influenced each other. Additionally, each work has a Technical Examination Report, which begins with an Overview, noting basic information about the object and identifying the conservator/conservation scientist who undertook the detailed analysis. This is followed by a section identifying Distinguishing Marks on both front and back of the painting, including images of the “marks” in question. These include inscriptions, stamps, labels, etc. A Summary of Treatment History outlines the documentary and physical evidence of past treatment interventions. The Current Condition Summary discusses the condition of the work at the time of examination. A table identifying Methods of Examination, Imaging, and Analysis used to examine each object follows.
A section on the painting’s support (Description of Support and Condition of Support) discusses materials and construction of the support and auxiliary supports as well as their condition and presumed (or confirmed) age. The section on the ground layer (Description of Ground and Condition of Ground) discusses the materials and application of the preparatory layers as well as the stability and condition at the time of examination. The section on the Description of Composition Planning discusses any underdrawing, preparatory layers, and pentimenti that were observed during the examination of the object. The section on the paint layer (Description of Paint and Condition of Paint) includes analysis of the binding media and pigments as well as a discussion of the techniques and tools used by the artist to create the work and a discussion of the condition of the original paint layer. The coatings section (Description of Varnish/Surface Coating and Condition of Varnish/Surface Coating) describes the layers of varnish, dirt, and other surface materials as well as inpainting, retouching, and overpaint present along with the condition of the surface coatings at the time of examination. Finally, the frame section (Description of Frame and Condition of Frame) discusses the presumed age, style, construction, and condition of each frame. There is a Distinguishing Marks section for labels, stamps, inscriptions, etc. found on the frames. These marks are numbered sequentially with any already noted at the beginning of the report.
In addition to being examined and photographed in visible light (front and back), raking light (front), ultraviolet-induced visible fluorescence, reflected infrared photography, visible induced infrared photography, reflected UVA photography, and X-radiography, paintings were also examined with a stereomicroscope. Frames were photographed (front and back) in visible light and using X-radiography (where appropriate). Each work underwent pigment analysis using macro X-ray fluorescence scanning (MA-XRF), and in select cases, cross sections were taken and analyzed using SEM-EDS. In some cases, pigments and ground materials were analyszed using Raman microspectroscopy. Binding media were analyzed where appropriate using FTIR. Colorimetry was also performed in selected caes.
Equipment used to carry out analysis for this catalog include:
Cross-section analysis:
Cross sections of paint layers were prepared by mounting an excised sample in Buehler Epoxi-cure mounting medium. The samples were pre-oriented in the mounts using a drop of fast-drying Superglue. Once the poured resin had cured fully, the section was polished on Micromesh cloth up to 12,000 grit fineness. Darkfield images of the sectioned samples were acquired on a Zeiss AxioImager M2m compound microscope with a 20X objective using an MRc5 digital photomicrography camera. The same area was then examined under UV irradiation from an X-cite 120Q mercury vapor lamp source for signs of visible luminescence. A DAPI filter cube set allowed narrowband excitation between 325 and 375 nm with observation throughout the visible spectrum (λem > 412 nm).
Fourier transform infrared (FTIR):
Fourier transform infrared (FTIR) microspectroscopy was performed on a Continuum microscope with a liquid nitrogen cooled MCT A detector coupled to a Nicolet 6700 spectrometer purged with dry, CO2-free air. The spectra are the sum of 32 coadditions at 4 cm-1 spectral resolution. Microsamples were crushed on a diamond compression cell and held on a single diamond window during the analysis. Sample identification was performed using the Infrared and Raman Users Group (IRUG) reference spectral library.
Fourier transform infrared (FTIR) spectroscopy was performed using a SpectraTech Smart Orbit diamond ATR attachment coupled to a Nicolet 6700 spectrometer with a mid-IR DTGS detector. The instrument was purged with dry, CO2-free air. The spectra are the sum of 64 coadditions at 4 cm-1 spectral resolution. Sample identification was performed using the Infrared and Raman Users Group (IRUG) reference spectral library.
Raman microspectroscopy:
Raman spectra were acquired using a Bruker Senterra microspectrometer on a Z-axis gantry. The spectrometer uses three selectable excitation lasers (532, 633, and 785 nm), an Andor Peltier-cooled CCD detector, and a 50 μm confocal pinhole. Laser power at the sample was generally below 5mW. The spectra are the result of 5 or 10 sec integrations with 5–30 coadditions. A 50X ultra-long working distance objective was used to focus slightly below the varnish layer on select pigment particles. The analysis spot size was on the order of 1 μm, and the spectral resolution was in the range of 9-18 cm-1. OPUS software allowed for automated cosmic spike removal, peak shape correction, and spectral calibration.
Scanning electron microscopy with energy dispersive spectrometry (SEM-EDS):
Electron micrographs of cross sections were created using a Zeiss EVO MA15 scanning electron microscope operated in variable pressure mode at 50 Pa of room air. A five-segment backscattered electron detector (BSE), a variable pressure secondary electron detector (VPSE), and a Bruker XFlash 6 energy dispersive spectrometer (EDS) with 60mm2 area were used to acquire images. Electron accelerating voltage was set at 20 keV to ensure generation of X-rays for all metals in the sample with a beam current of 1.2 nA. A sample working distance of 8.5mm optimized EDS detection. The SEM was controlled using Zeiss SmartSEM software while the EDS spectra were collected and analyzed using Bruker Esprit 2.0 software.
X-ray fluorescence (XRF):
A Bruker Artax microfocus XRF with rhodium tube, silicon-drift detector, and polycapillary focusing lens (~70 μm spot) was used in the analysis. Experimental parameters included 50 keV tube voltage, 600 μA current, and 60 sec live time acquisitions. A helium purge gas allowed for light element detection. Elemental survey spectra were collected in the region from 0 to 50 keV.
Point analyses and elemental maps were acquired on a Bruker M6 Jetstream macro-scanning XRF with rhodium tube, dual 60 mm2 silicon-drift detectors, and polycapillary focusing lens (selectable 540 to 100 mm spot). Experimental parameters included 50 keV tube voltage, 600 mA current, and 45 msec/pixel scan rate. Elemental spectra were collected in the region from 0 to 40 keV.
A Bruker Tracer 5i handheld XRF with rhodium tube, a large area silicon drift detector, and a 3 or 8mm collimator was used in the analysis. Experimental parameters included 40 keV tube voltage, 100 μA current, and 60 sec live time acquisitions. A vacuum attachment allowed for light element detection. Elemental survey spectra were collected in the region from 0 to 40 keV.
Macro X-ray fluorescence scanning (MA-XRF):
Point analyses and elemental maps were acquired on a Bruker M6 Jetstream macro-scanning XRF (MA XRF) with rhodium tube, dual 60 mm2 silicon-drift detectors, and polycapillary focusing lens (selectable 540 to 100 mm spot). Experimental parameters included 50 keV tube voltage, 600 mA current, and 45 msec/pixel scan rate. Elemental spectra were collected in the region from 0 to 40 keV. Maps were prepared from deconvoluted and background corrected spectra. Overall image intensities were manipulated to enhance readability of the maps.
Pyrolysis–gas chromatography–mass spectrometry (PY-GC-MS):
A small scraping of paint was characterized by PY-GC-MS. The sample was analyzed using the method similar to Tsuge et al. In short, a Frontier Lab PY-3030D double-shot pyrolyzer system with a 320oC interface was coupled to a Thermo Trace Ultra gas chromatograph and an ISQ single quadrupole mass spectrometer. A Thermo TG-5MS capillary column (30 m x 0.25 mm x 0.25 µm) was used for the separation with 1 mL/min of He as the carrier gas. The split injector was set to 250oC with a split ratio of 100:1. The GC oven temperature program was 40oC for 2 min, ramped to 320oC at 20oC/min, followed by a 13 min isothermal period. The MS transfer line was at 320oC, the source at 230oC, and the MS quadrupole at 150oC. Mass spectra were collected from 29–250 amu for the first 3 min and from 45-600 amu thereafter. The electron multiplier was set to the auto-tune value. Samples were placed into a 50 µL stainless steel Eco-cup and pyrolyzed at 600C for 6 sec. If necessary, the sample was derivatized on-line using 3 μL of 25 wt% tetramethylammonium hydroxide (TMAH) in methanol from Sigma-Aldrich and allowed to dry before introduction into the pyrolyzer. In all instances, the sample cup was purged with He for at least 3 min in the microfurnace prior to pyrolysis. For derivatized samples, a 3 min solvent delay was added to the run prior to activating the MS. GC peak identification was aided by searching the NIST MS library and by comparison to pyrograms of authentic samples.
Colorimetry:
Color measurements were made using a handheld Konica Minolta CM-700d spectrophotometer. The unit uses a pulsed Xe flashbulb source positioned for 8º diffuse illumination in an integrating sphere. An 8mm circular area of the painting was examined. Sample measurements are compared against a white reflective tile. The resulting spectra span 400-700nm at 10 nm resolution. CIE Lab* color coordinates were calculated using D65 illuminant, 10-degree observer, specular component excluded, and DE2000 color different equation.