Underdrawings and pentimenti reveal intermediate states of a painting and thus may shed light on the working
methods of some artists. It has been claimed that Lorenzo Lotto used optical projections during the execution
of Husband and wife (1543) and, recently, that underdrawings in that work might reveal evidence of tracing
of optical projections. We analyze x-ray images of this painting-captured under careful, museum-laboratory
conditions and enhanced through digital image processing-with special attention to the possibility of evidence
of the use of optical projections in the central passage of the depicted carpet. We also study the work in situ and
in high-resolution macro optical images of the central portion of the carpet pattern. These photographs reveal
that the top portion of the keyhole pattern is not "blurry, like an out-of-focus image," but instead was merely
executed in a somewhat broader brush than was neighboring passages. Furthermore, x-ray, infra-red and visible
light inspection show that the white portions and black contours were executed atop a broad layer of dark red and
reveal no record of an optical projection would have been present when Lotto executed the visible portion. As
such, an evidence of putative underdrawings in this region has no bearing on the optical projection claim. There
is no evidence of tracing marks-in charcoal or in any medium-in the top, visible portion of this passage either.
As such, this visual, infra-red and x-ray evidence does not support the claim that this painting was executed
under optical projections. We also discuss the difficulties with the projection theory with special reference to
Lotto's preparatory drawing in the Rijksmuseum-specifically the need for a needlessly complex optical system
(two lenses rather than one). We also review briefly contemporary textual evidence in early 16th-century Venice
that has been used to support the optical projection claim for Lotto and conclude that it also fails to support
the projection claim for this painting.
The archaeological gold contains usually 10 - 80 ppb U238 as a trace element. Under radioactive decay U238 produces approximately 3.7 alpha particles in 1 mg of metal containing 1 ppb of U238 per one year. The a-particles (as He4) are accumulated inside the metal as gold appears to be extremely retentive for He. When the metal is heated to its melting point all accumulated helium escapes thus establishing 'zero-time' for the He-radiogenic clock. This way the clock starts at the point when the object is manufactured. The new ultrasensitive He-recycling mass-spectrometer providing the sensitivity approximately 2.5(DOT)104 He-atoms has been developed and manufactured for the museum usage. Taking a gold sample of 5 - 10 mg with typical 10 ppb U content in gold one can expect to find 185,000 - 370,000 He atoms in metal manufactured 1000 years ago. These quantities can be easily detected by the instrument thus providing rather reliable authentication (and in some cases -- absolute dating) tool for detection of fakes.
The Kodak DCS460IR Digital Camera has been applied in the Hermitage Museum for photographing the museum objects in visual luminescence under UV, in the near IR and for X- radiography in the 10 - 80 kV range using the fluorescent screens. We found the instrument to suit quite well for the qualitative examination, providing the possibility for substitution of the corresponding conventional photographic materials. In case of the near IR the sensor permits to work in the range where the infrachromatic materials are not commercially sensitized. The quantitative estimates for the images were difficult at the same time.
Conference Committee Involvement (8)
Optics for Arts, Architecture, and Archaeology (O3A) VIII
21 June 2021 | Online Only, Germany
Optics for Arts, Architecture, and Archaeology VII
24 June 2019 | Munich, Germany
O3A: Optics for Art, Architecture, and Archaeology
28 June 2017 | Munich, Germany
Optics for Arts, Architecture, and Archaeology V
24 June 2015 | Munich, Germany
Optics for Arts, Architecture, and Archaeology IV
15 May 2013 | Munich, Germany
O3A: Optics for Arts, Architecture, and Archaeology
25 May 2011 | Munich, Germany
O3A: Optics for Arts, Architecture, and Archaeology
17 June 2009 | Munich, Germany
O3A: Optics for Arts, Architecture, and Archaeology
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