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Thursday, May 16 • 2:00pm - 2:30pm
(Tough Challenges Need New Techniques) The Dating Game: A New Diagnostic Marker for Dating and Provenancing of Titanium White Pigments

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Titanium dioxide was the white pigment of the 20th century. Non-toxic, inexpensive, and with high covering power, it was everything that zinc and lead white pigments were not. Although synonymous with ‘modern art’ (roughly from the 1860s to the 1970s), close assessment of titanium dioxide can provide dating information because changes in manufacturing chemistry altered the compositions of available pigments in well-defined ways. The first titanium white pigment produced in the United States was the anatase form co-precipitated onto barium sulfate (1916). The anatase form co-precipitated onto calcium sulfate was introduced by 1925, and pure anatase itself was widely available by 1927. The rutile form, which has a higher refractive index and greater coloring power, was at first more difficult to manufacture, co-precipitated rutile pigments were introduced in 1941, and the pure rutile species in 1957. Anatase co-precipitates were reportedly phased out in the 1940s, while production of the rutile calcium sulfate co-precipitate continued until the 1970s. Accordingly, the crystal form of the titanium dioxide, which is easily and non- or minimally- destructively determined by Raman spectroscopy, provides some dating information. Determining whether the pigment is co-precipitated would allow more precise dating, but mere co-detection of barium or calcium sulfate with titanium dioxide is inconclusive: sulfates are commonly used fillers that might be mechanically added to titanium dioxide paint. Fortunately, some titanium dioxide pigments bear within them trace elements that can serve as markers for the source of the titanium ore and their method of manufacture. Recent technical studies on abstract expressionist paintings at the Museum of Fine Arts, Houston, the Menil Collection and the Metropolitan Museum of Art revealed a luminescence signature from titanium white paints whose pigment had been manufactured by co-precipitation with calcium or barium sulfate. We propose that trace neodymium, a rare earth element present in some ilmenite (FeTiO3) ores, can become trapped in the sulfate during co-precipitation, generating a luminescent marker characteristic of both the ore and the process. The luminescence is linked to a specific ilmenite source used in historic Titanox® pigments manufactured in the USA, permitting identification of the mineral source (similar to trace element analysis of obsidian, marble, or lapis lazuli). The signature is not present in pigments produced by more advanced chemistries, allowing identification of the manufacturing method. Facile Raman-based detection of this luminescence along with characteristic peaks of the sulfate and rutile or anatase can unambiguously identify the titanium white pigment and narrow its manufacture date range. A survey of 109 paintings of known provenance created between 1926 and 1986 reveals that the manufacture dates inferred from the luminescence are consistent with the production dates for these works. The luminescence frequently occurs in paintings by well-known artists including Franz Kline, Hans Hofmann, Barnett Newman, Andy Warhol, Robert Rauschenberg, and Jackson Pollock, artists whose works currently sell for millions of dollars and are targets for forgers as illustrated by the recent Knoedler Gallery scandal. This luminescence, therefore, represents a new, valuable tool for assessing the age and origin of an artwork.

avatar for Dr. Corina E. Rogge-[PA]

Dr. Corina E. Rogge-[PA]

Andrew W. Mellon Research Scientist, The Museum of Fine Arts, Houston
Corina E. Rogge is the Andrew W. Mellon Research Scientist at the Museum of Fine Arts, Houston and the Menil Collection. She earned a B.A. in chemistry from Bryn Mawr College, a Ph.D. in Chemistry from Yale University and held postdoctoral positions at the University of Wisconsin-Madison... Read More →

avatar for Julie Arslanoglu

Julie Arslanoglu

Research Scientist, The Metropolitan Museum of Art
Julie Arslanoglu is a Research Scientist in the Department of Scientific Research at the Metropolitan Museum of Art. She investigates paints, coatings, adhesives and organic materials from artworks across all ages with spectroscopic, mass spectrometric and immunological techniques... Read More →

Thursday May 16, 2019 2:00pm - 2:30pm EDT
Salon B2, Uncas Ballroom
  General Session, Tough Challenges Need New Techniques
  • Ticketed Included in Main Registration
  • Authors in Publication Order Corina E. Rogge, Julie Arslanoglu
  • Abstract ID 18469
  • Tags Raman spectroscopy,modern art,titanium white,dating