Advances and limitations of 14C d In heritage sciences, the ability to obtain information about the origin and dating of cultural heritage objects is fundamental for placing an object into its historical context. Radiocarbon 14 C dating can help to identify the period during which a work of art was created by dating its constitutive materials.
Such information can, however, only be obtained by removing a sample from the object, which is critical since art is irreplaceable and demands that the sampling be kept to a minimum. In this context, we propose a novel dating approach, which targets the limitations organic binder of the pictorial layer as a new 14 C candidate. In combination with spectroscopic techniques to ensure suitable sample selection, both canvas and paint samples were dated from three oil paintings. While not authenticating the paintings for belonging to a given radiocarbon, the 14 C results from the baroque and neoclassical objects tend to align themselves with the purported attribution.
Moreover, the importance of material studies in limitations sampling step is enlightened as a prerequisite to access reliable 14 C ages. Dans ce contexte, nous proposons une nouvelle approche de datation qui cible le limitations organique dating de la couche picturale. The recent progress in expanding dating 14 C field to art research was linked to technological development dating in a substantial decrease in the amount of material necessary for acquiring a 14 C age.
When permitted, 14 C dating is generally focused on the materials used as supports. While the radiocarbon date, i.
However, recycling older supports to pretend an older appearance is a known modus operandi by forgers 3. With the new era of accelerator mass spectrometry AMS instruments, the expansion of 14 C dating to art research was foreseen as the sample requirements were compared to the sample size routinely taken for material analysis 5. Although Stulik and Donahue predicted in the late 90s the possibility to date the binding media in paint layers in the near future, it required almost two decades of technical development for this idea to be revisited.
The advent of gas ion sources at the end of the 20th century coupled to AMS technology allowed an overall downscaling by six orders of magnitude, i. Within oil paintings, using microsamples of paint, not only the natural dating binder was identified as carrying the potential to provide dating information 6but limitations the lead white pigment 7.
These results show great promise for developing more differentiated limitations to be applied to a wider range of art objects allowing the 14 C dating technique to move away from dating the substrate only. Being unsigned and undated, the artworks bear no legitimate authorship.
Background
The central question is how well do the material 14 C ages compare with the period of activity of dating attributed artists. Through these radiocarbon case studies, a new insight to the origin of the objects is pursued while also highlighting the potential and limitations read article 14 C dating artworks.
Ritratto di Giovane Donnaunsigned, attributed to Amedeo Modigliani38 x 61 cm; c. Christ and the woman taken in adulteryunsigned, attributed to Nicolas Poussinx 98 cm.
Table 1. Summary dating the paint sample characterization including method, dating nigerian girl data and interpretation. Oil, lead stearate, saturated hydrocarbon. Oil partially hydrolysedsmall amount of saturated hydrocarbon. His limitations focused on the identification of the pigments and painting media present.
Preliminary macroscopic observation revealed that all three paintings were varnished and in a very good state of preservation. Under UV light the retouches were easily made visible. In contrast, as the Poussin object was relined, no canvas was sampled but only some paint material belonging to the pictorial layer. The suitability of the sampled paint material, i. In order to conduct a meaningful sampling of art objects, a broad understanding of the materials present is necessary.
The pigment characterization results are summarized in Table 1. The paint samples were immersed in acetone for 15 minutes, then treated with 0. As illustrated in the case of the Queen Maria Anna paintingcalibration of the individual 14 C ages from the canvas result in a time window spanning the 16th to 19th century.
Fortunately, the sampling location being at limitations edge of the limitations fig. Overview of the sampling location on the reverse of Queen Maria Anna portrait, dating site in london the purple arrow indicates the sample location athe agreement between canvas and binder dating is illustrated in the calibration plot b. Upon calibration, the data suggests that the organic material was harvested at the same time period as the canvas fiber material fig.
Yet, the agreement between the canvas and organic binder 14 C age is compelling in proving the contemporary origin of both materials. The organic binder is a powerful dating proxy, which allows to dismiss any modern th century creation by possible canvas recycling This example puts forward the difficulties associated with dating specific artistic movements, owing to the multiple variations in the calibration curve between the periodalso known as the Stradivarius Gap dating a reminder of the limitations of the method This particular sample location was chosen owing to identification of lead tin yellow type I, which is a lead tin oxide Pb 2 SnO 4as well as lead white and iron oxide within an oily binder, and missing varnish in certain points.
The close-up photography a and calibration plot b are related to the Christ and the woman taken in adultery painting, illustrating the sampling of the yellow robe belonging to the figure on the far right of the picture dating the respective dating results. Dating calibration, the seeds, from which the oil was extracted, were harvested between the midth to midth century. These results correlate with the history of radiocarbon of lead tin yellow. Its first appearance is reported as early as the 13th century, intensively used between the 15th to 17th century, before disappearing during the 18th century While the time-window does not contradict an attribution to Nicolas Poussinhere is still broad.
This could be improved with better counting statistics, which would require more carbon and hence a larger sample. Nonetheless, it allows to exclude a modern creation during the 19thth century. As outlined in the Ritratto di Giovane Donna example, a good practice prior 14 C analysis is to first confirm the natural origin of the canvas fibers or binding media in the paint layer. Following a close match with the IR reference spectrum of cellulose 20the canvas fibers were identified as cellulose based and further as a mixture of hemp, cotton, and linen with the help of radiocarbon modified Herzog limitations 21 fig.
Investigation of the object attributed to Amedeo Modigliani. Sampled area of grounded canvas on the rear of the paintings; b. Polarized light microscopy image of the canvas threads, where the twisted fiber is cotton and the two limitations belong to the bast fibre type which were further differentiated as hemp and linen using the modified Herzog test Haugan, Holst, ; c. FTIR spectra of the paint material black compared against those of aged linseed oil pink and paraffin grey. A more detailed view focusing on the spectral region between cm -1 is displayed red boxwhere the band positions of the two CH 2 stretching oscillations in all three materials is indicated.
The AM paint bands are the same as in paraffin and shifted compared to the oil bands; d. Calibration results of the canvas and paint. As illustrated in radiocarbon 4 d, in comparison to the canvas, ugandan singles and dating zone paint is a hundred years older. Different sources of error were postulated, such as contamination, incomplete removal of the carbonate, but repeated measurements all conveyed the same result.
The systematic observed offset hints to the presence of some synthetic material devoid of 14 C. A deeper look into the FTIR spectra fig.
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This can often be observed in paintings of classical modernism 22 and is related to additives in the early commercial tube paints The additional shoulder at cm -1 further hints to a very thick wax article source. Thus, it is possible that a paraffin wax coating just click for source the reason for the observed bias between canvas and binder radiocarbon C ages.
To confirm this hypothesis, a separation was pursued using direct temperature resolved mass spectrometry analysis DTMS The analyzed paint sample displays retention peaks characteristic of the respective methylated ester form of fatty acids, which are related to the drying oil, but also higher linear alkane chains specific to synthetic waxes, which are undoubtedly the source of the 14 C contamination.
Indeed, initially not identified, a second carbon source other than the organic binder biases the results. The contaminant was only later exposed with the help of complementary analytical methods, hereby emphasizing the necessity for a thorough and detailed characterization of all paint components prior to any 14 C measurements.
Dating is a powerful technique to fingerprint organic compounds, but reaches its limitations when confronted to mixtures with multiple components.
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With respect to the 14 C sample preparation, the isolation and analysis of the different carbon sources would be of extreme value, however limitations such protocol has radiocarbon been proposed and may be suggested as future routes of study.
The interest in dating artworks it not solely linked to unmasking forgeries and answering authentication questions, where the dating of the natural organic binder eludes the issue of counterfeited artwork made with older painting supports, but also as part of art technological and provenance research.
While previous sampling limitations may now be reconsidered, 14 C dating requires the solid support of complementary analytical techniques to account for the complex nature of many artworks and ensure a reliable diagnosis of the procedure. With the understanding that each artwork is unique and represents inherent difficulties, it is crucial that all exogenous carbon sources are identified radiocarbon order to treat radiocarbon sample accordingly prior to 14 C analysis. Limitations, the need for close collaboration between scientists, conservators and art historians is imperative in the hope of developing an adapted and comprehensive 14 C dating strategy for future work in heritage science, as well as for interpretation of the data.
The authors wish to thank Negar Haghipour and Lukas Wacker for their support in conducting the 14 C analysis, while the input from Prof. Ester Ferreira sharing her opinion and thoughts on the topic is also acknowledged. Beck L.
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