Tracing Medieval and Renaissance Alabaster Works of Art Back to Quarries: A Multi‐Isotope (Sr, S, O) Approach

Abstract

Multi-isotope fingerprinting (sulphur, oxygen and strontium isotopes) has been tested to study the provenances of medieval and Renaissance French and Swedish alabaster artwork. Isotope signatures of historical English, French and Spanish alabaster source quarries or areas reveal highly specific, with a strong intra-group homogeneity and strong inter-group contrasts, especially for Sr and S isotopes. The chosen combination of isotope tracers is a good basis for forensic work on alabaster provenance allowing verification of hypotheses about historical trade routes as well as identification of fakes and their origin. The applied analytical techniques of continuous flow isotope ratio mass spectrometry (CF-IRMS) and thermal ionisation mass spectrometry (TIMS) only require micro-samples in the low mg range thus minimising the impact on artwork.

Adapted ageing tests for the evaluation of alabaster used in the restoration of Bishop’s Palace of Tarazona

“…Due to the translucency and the small thickness of the samples, the temperature gradient was negligible, and all the crystals dilated and contracted at the same time. In addition, textural features such as straight grain boundaries or heterogeneous grain size (6,20,21) which favor bowing did not appeared in the studied samples.…”

“…This mineral anisotropy is the responsible to stone deformation forming surface grooves (3) and sometimes bowing (4). This phenomenon is commonly found in calcitic crystalline stones like marbles (5), although in other polycrystalline stones as granites was also recognized (6). This particularity, added to its high dissolution potential, makes alabaster extremely susceptible to decay, and consequently it is used mainly in sculptures and other indoors ornaments.…”

In search of the lost polychromy of English medieval alabaster panels in the Southwest of France

“…Other archaeometric papers on alabasters are not directly related to the study of polychromy. They examine their provenance by comparing the composition of alabaster quarries and that of the panels preserved in France and Switzerland, based on the dosage of trace elements such as strontium and sulfur …”

“…They examine their provenance by comparing the composition of alabaster quarries and that of the panels preserved in France and Switzerland, based on the dosage of trace elements such as strontium and sulfur. 24 These recent papers on polychromy illustrate the benefits of a deeper knowledge of medieval polychromies by a multidisciplinary approach, namely the collaboration of art historians and archaeometrists. This collaboration seems essential in order to avoid misinterpretations in examining colors that have generally altered over time.…”

Competing English, Spanish, and French alabaster trade in Europe over five centuries as evidenced by isotope fingerprinting

“…Our pilot study ( 19 ) tested isotope fingerprints (Sr, S, O) as an independent method to link artworks to their source areas, and developed an associated analytical protocol: Tiny flakes (<20 mg) of alabaster are dissolved in distilled water at 50 °C, and the dissolved sulfate is precipitated as BaSO 4 for S- and O-isotope analysis by continuous flow isotope ratio mass spectrometer (CF-IRMS). Aliquots of the solutions are purified by ion exchange for Sr-isotope analysis by thermal ionization mass spectrometer (TIMS).…”