Research ArticleAPPLIED SCIENCES AND ENGINEERING

Luminescence of coprecipitated titanium white pigments: Implications for dating modern art

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Science Advances  17 May 2019:
Vol. 5, no. 5, eaav0679
DOI: 10.1126/sciadv.aav0679
  • Fig. 1 Artworks and historic paints exhibit strong luminescence bands in Raman spectra.

    Raman spectra of titanium white paint and pigment samples taken with a 785-nm laser display peaks due to CaSO4, anatase (sample from Green Composition), or rutile (Corinthian II and the TITANOX RCHT pigment) and the luminescence peaks, which are marked with “*.” The manufacturer’s information indicates that the TITANOX RCHT pigment is 30% rutile coprecipitated with CaSO4 (27).

  • Fig. 2 Luminescent titanium white paint samples from four works of art contain similar levels of certain REEs.

    ICP-MS was used to determine REE concentrations in samples of coprecipitated titanium white paints from Untitled #525 (1961) and Thanksgiving (1960) by Ray Parker, Wotan (1950–1951) by Franz Kline, and Fiat Lux (1963) by Hans Hofmann and in a sample of Grumbacher Titanium White paint. All samples contain the rutile form of TiO2, except for that from Wotan, which contains both rutile and anatase phases.

  • Fig. 3 REE levels vary widely in ilmenite ores.

    ICP-MS was used to determine concentrations of REEs in ilmenite ore samples from the McIntyre mine (New York), the Faraday mine (Canada), Egersund (Norway), and the Middle Atlas Mountains (Morocco). Error bars indicate SEM (n = 3).

  • Fig. 4 REE levels are similar in an ore, a coprecipitated pigment, and paints from works of art.

    Concentrations of REE in different samples of TITANOX pigments compared to those of the ilmenite from the McIntyre mine (New York) and average concentrations of the four paintings analyzed in Fig. 2. Error bars on the TITANOX and ilmenite samples indicate a 5% instrumental error, while those on the painting average indicate SD of the four different paint samples. REE levels in the pure pigment TITANOX RA are within the detection limits of ICP-MS but comparatively low (for Nd, 25 ng/g), so bars are nearly invisible on this scale. The same data are presented on a log scale in fig. S3.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/5/eaav0679/DC1

    Fig. S1. Luminescence bands shift and change intensity with laser energy.

    Fig. S2. Timeline for occurrences of six white pigments in American works of art.

    Fig. S3. REE levels in an ilmenite ore are similar to those in coprecipitated titanium white pigments and paints from works of art.

    Table S1. Timeline of titanium oxide pigment manufacture in the United States.

    Table S2. Raman shifts and luminescence wavelengths generated by different lasers.

    Table S3. TITANOX titanium dioxide pigment compositions and species detected by Raman spectroscopy.

    Table S4. Works of art displaying luminescence peaks indicative of coprecipitated pigments.

    Table S5. Analysis of titanium white oil paints from NGA-MSRC.

    Data file S1. Rare earth concentrations in samples of ilmenite ores, TITANOX pigments, and samples of paint as determined by ICP-MS.

    Reference (41)

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. Luminescence bands shift and change intensity with laser energy.
    • Fig. S2. Timeline for occurrences of six white pigments in American works of art.
    • Fig. S3. REE levels in an ilmenite ore are similar to those in coprecipitated titanium white pigments and paints from works of art.
    • Table S1. Timeline of titanium oxide pigment manufacture in the United States.
    • Table S2. Raman shifts and luminescence wavelengths generated by different lasers.
    • Table S3. TITANOX titanium dioxide pigment compositions and species detected by Raman spectroscopy.
    • Table S4. Works of art displaying luminescence peaks indicative of coprecipitated pigments.
    • Table S5. Analysis of titanium white oil paints from NGA-MSRC.
    • Legend for data file S1
    • Reference (41)

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    Other Supplementary Material for this manuscript includes the following:

    • Data file S1 (Microsoft Excel format). Rare earth concentrations in samples of ilmenite ores, TITANOX pigments, and samples of paint as determined by ICP-MS.

    Files in this Data Supplement:

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