The Evidence: Surface

Crystallization vs. Oxalic Acid Polishing: Floor Care Tech Talk

3M Crystallization vs. Oxalic Acid Polishing

Getty Kouros

The Getty Kouros

      Perhaps the most important and unusual feature of the kouros is its pale, chalky surface. In 1987, Marion True published an article arguing in favor of the Getty kouros's authenticity based on a series of scientific tests conducted on its abnormal surface, rejecting arguments based in visual analysis and noting that the similarities between the Anavysos kouros and the Getty kouros were only superficial.[1] The stone used to carve the Getty kouros is dolomitic marble found on the island of Thasos. According to True, scientists removed samples from the left shoulder and right knee in order to conduct tests on the material. They concluded that "natural ground water" had leached out the magnesium the dolomitic marble naturally contains over the course of centuries, leaving behind an outer shell of calcite. Since dolomitic marble is much less porous than other marble types, it is much easier for this type of crystallized crust to form over the top.[2] This process of de-dolomitisation, according to the scientists conducting the tests, could not be duplicated with modern science. Furthermore, iron-bearing clay was discovered on the dolomite crystals, which to True, suggested that the statue had been buried for some time and must therefore be authentic.

       While scientific analysis is important, it must be evaluated in its own right. Stylistic analysis, or connoisseurship, cannot always determine a fake on its own. Sometimes science is necessary to augment this approach. Yet to completely rely on the results of these tests can be dangerous. The supposed objectivity offered by science is more universally accepted a definitive proof than intuition-based connoisseurship, but that does not always mean that science is free of bias or inaccuracies. The problem is figuring out which types of tests are the most beneficial to the situation and, when the tests are completed, how to interpret the results.[3]

       For example, more recent examination of the Getty kouros's exterior has revealed the outer layer as calcium oxalate rather than the result of de-dolomitisation. Calcium oxalate is created when dolomitic marble is exposed to oxalic acids.[4] Thus the aged effect on the outer layer of the kouros could be faked in a relatively short amount of time. Kenneth Lapatin notes that "potato and other vegetable molds can transform the surface of dolomitic marbles in a matter of months."[5] In fact, oxalic acid solutions have been used since the 1960s to polish marble and travertine floors through a process labeled crystallization.[6] Thus such a substance may have been very easy for forgers to obtain and use on the marble. However, no researcher has yet been able to recreate the recipe a forger may have used on the statue with the same resulting chemical structure as the Getty kouros. Though though the marble could have been "cooked," the method of "cooking" is still in question.[7]

       The application of oxalic acid onto marble also changes the chemical structure of the stone, meaning that removing the layer of calcium crystal would be extremely difficult if not impossible. Currently, there is no evidence of paint, which was typically applied to all archaic kouroi, remaining on the Getty kouros.  If any remnants of ancient paint survive, they may be underneath the calcium layer. Unfortunately, it may be impossible for these remnants to survive if the outer shell of calcium is ever removed. The fact that the outer layer is not de-dolomitisation but rather calcium oxalate is not proof of forgery alone, but rather disproves previous arguments for the statue's authenticity.

 


 [1] True, "A Kouros at the Getty Museum," 8.

[2] Ibid., 11.

[3] Spier "Blinded with Science: The Abuse of Science int he Detection of False Antiquities," The Burlington Magazine 132.1050 (1990): 628.

[4] Lapatin, "Proof?: The Case of the Getty Kouros," 47.

[5] Ibid., 50

[6] 3M Building and Commercial Services Division, "Crystallization vs. Oxalic Acid Polishing: Floor Care Tech Talk," last modified March, 2012, http://multimedia.3m.com/mws/media/790119O/crystallization-vs-oxalic-acid-polishing.pdf

[7]Lapatin, "Proof?: The Case of the Getty Kouros," 50.

 

The Evidence: Surface