Volumes of Worth—delimiting the Sample Size for Radiocarbon Dating of Parchment

Abstract

Medieval manuscripts are invaluable archives of the written history of our past. Manuscripts can be dated and localized paleographically, but this method has its limitations. The Fragmenta membranea manuscript collection at the National Library of Finland has proved difficult to date using paleographic methods. Radiocarbon dating has been applied to manuscripts of parchment before, but a systematic protocol for radiocarbon dating of parchment has not been established with a minimally destructive sampling strategy. In this work, we have established a radiocarbon dating procedure for parchments combining a clean-room based chemical pretreatment process, elemental analyzer combustion, automatic graphitization and accelerator mass spectrometry (AMS) measurements to reduce the AMS target size from a typical 1 mg of carbon. Prolonged acid treatment resulted in improved dating accuracy, since this is consistent with the manufacturing process of medieval parchment involving a lime bath. Two different combustion processes were compared. The traditional closed tube combustion (CTC) method provided a well-established though labor-intensive way to produce 1 mg AMS targets. The Elemental Analyzer-based process (EA-HASE, Elemental Analyzer Helsinki Adaptive Sample prEparation line), is designed for fast combustion and smaller sample sizes. The EA-HASE process was capable of reproducing the simulated radiocarbon ages of known-age samples with AMS graphite target sizes of 0.3 mg of carbon, corresponding to a 3 mm2 area of a typical medieval parchment. The full potential of the process to go down to as little as 50 μg will be further explored in the future in parallel to studies of sample-specific contamination issues.

Radiocarbon dating

“…The characteristic complications of the calibration curve -which plague the last 500 years of the time scale 8 and form the Vinci and Stradivarius age plateaus [G] 51 -increase the age range of numerous artworks when their radiocarbon ages are calibrated. Nevertheless, the need for radiocarbon dating of manuscripts, paintings, textiles, statutes, musical instruments and objects of everyday use such as furniture and buildings is growing and treatment methods to optimize both sample size of various materials and precision are being developed 264 (Supplementary Table 2). Removal of exogenous carbon such as varnishes or consolidation material using solvents is crucial for accurate and precise dating and for the detection of forgeries [265][266][267][268] .…”

A Glance to the Fragmenta Membranea Manuscript Collection Through Ftir and Radiocarbon Analyses

“…Some exceptions occur, to mention the fragments of the printed Missale Aboense that have a very narrow and highly reliable reference dates of AD 1478-1488, as Missale Aboense is known to have been printed in Lübeck by Bartholomeus Ghotan in 1488 (Heikkilä 2010). This timeframe also corresponds to our reference materials of AD 1471 and AD 1506 used also in Kasso et al (2021). Therefore, we consider those samples also as suitable reference material to additionally monitor the quality of the process in our sample preparation.…”

“…However, sampling cultural heritage material such as medieval manuscripts for radiocarbon dating can be challenging due to the limited sample sizes allowed. Using known-age material, Kasso et al (2021) demonstrated that it is possible to obtain reliable radiocarbon dates of parchment samples down to 0.3 mg carbon targets for accelerator mass spectrometry (AMS), corresponding to typically ca. 3 mm 2 area parchment sample sizes.…”

“…This allows minimal sampling and prevents unnecessary destructive intervention to the object. In this study, we apply our previous method (Kasso et al 2021) to a large set of samples and evaluate our results from the viewpoint of the applicability of radiocarbon dating as an absolute dating method parallel to traditional methods in dating medieval manuscripts. Moreover, we address the challenges when working with fragmentary parchment material and underline the necessity of pre-screening material prior to sampling.…”

“…Radiocarbon dating provides a scientific parallel to the traditional palaeographical estimation of the ages of the fragments. Combining these methods can potentially narrow down the age range of manuscripts extensively, and help to produce a more reliable timeline for the historical developments and information these objects contain (Kasso et al 2021).…”