Investigating Fluidizing Dripping Pink Commercial Paint on Van Hemert’s Seven-Series Works from 1990–1995

Abstract

A painting from the Seven series by Frank van Hemert made between 1990 and 1995 was starting to show fluorescent exudates and drips after about 7 years. Paint samples were investigated with analytical mass spectrometry, solid state NMR, imaging FTIR and SEM-EDX. Fluorescent exudate of fluidised paint compared to rubbery paint underneath showed differences in FTIR and MS characteristics related to the distribution of polar acylglycerides with ester bonded and free azelaic acid groups. The oil in the Schmincke Norma Fleischfarbe nr 213 tube paint used by van Hemert consists mainly of semidrying oil giving a Drying Index of 72. Imaging FTIR identified aluminium soaps in fluorescent vesicles in the solid rubbery paint. Solid state NMR indicated that these aluminium soaps are degraded and consist mainly of aluminium hydroxy-monostearates. DTMS and ESIMS showed apolarity inside the rubbery paint compared to the exuding material. The drying of the paint produced high relative amounts of smaller oxidised fractions that could not be retained in the paint mass as aging progressed. A physical separation resulted in more polar fractions. The fluorescence of these exuding fractions can be used a tracer for failing or impending failing of oil paint.

Appendix

Experimental Details

Microscopy

Light microscopic images (VIS and UV-fluorescent) were obtained with a Leica DMRX microscope (Leica, Wetzlar, Germany). The Bio-Rad Stingray (Bio-Rad, Cambridge, MA), combining the Bio-Rad FTS-6000 spectrometer equipped with a Bio-Rad UMA 500 infrared microscope with a 64 × 64 mercury-cadmium telluride (MCT) focal plane array camera was used to record the FT-IR images (see van der Weerd et al. 2005). A Philips-FEI XL-30 FSEM coupled to an EDAX energy dispersive analyser was used for SEM-EDX. The ion polished section (Boon et al. 2008) was covered with a few nm of gold in vacuo using a sputter coating system.

Mass Spectrometry

A JEOL SX102-102A mass spectrometer was used for DTMS (Direct Temperature resolved Mass Spectrometry) equipped with a Pt/Rh (9/1) filament (diam.100 μm) probe for in-source MS. Spectra were obtained at 16 eV electron ionisation over a mass range of 1,000 Da at a cycle time of 1 s and acceleration voltage of 8 kV (Boon 1992). Degree of esterification was determined by GCMS after derivatisation of paint samples using the method of Van den Berg et al. (2001). Tube paint was extracted with chloroform/methanol (3/1). Part of the extract was analysed directly with ESIMS. Another part subjected to basic hydrolysis, worked up and analysed by ESIMS or by GCMS after silylation. Paint samples were also weighed (400–600 microg) into 1 mL tapered vials. For ethanol extraction 100 microL ethanol was added with tridecanoic and tetradecanedioic acids as internal standards. The samples were extracted for 18 h under ambient conditions. Extract were analysed directly with ESIMS. Hydrolysis of ethanol extracts: a 0.1 M ethanolic NaOH solution with tridecanoic and tetradecanedioic acids as internal standards was added to the samples. The hydrolysis took place in an oven held at about 80 °C for 1.5 h. Each solution was shaken and centrifuged after extraction or hydrolysis. The extract or hydrolysate was subsequently transferred to a vial containing cation exchange resin (DOWEX HCR-W2 ion-exchange resin, Sigma–Aldrich) and left for 30 min to remove pigment-derived cations. The supernatant solution was removed from the resin and transferred to a new vial. For all ESIMS, Ethanolic ammonium acetate was added until a final concentration of 10 mM ammonium acetate was achieved.

Nano-ESI–QTOF–MS was performed on a Q-ToF2 instrument (Micromass Limited, Wythenshawe, UK). The solutions were sprayed with Econo10 needles or BG-10-58-2-CE-20 needles (New Objective, Woburn, USA) with a flow of approximately 10–80 nl/min. Data were processed using the MassLynx V3.5 software (Micro- mass Limited, Wythenshawe, UK). Mass spectrometer conditions: capillary voltage: 2 kV, cone voltage: 10 V, collision energy: 10 eV, TOF: 9.1 kV and the detector was set at 2,150 V in the positive mode and 2,300 V in the negative mode.