Chapter 3 T h e Å l a n d C h u r C h e s p r o j e ct a n d T h e n e C e s s i T y o f i n T e r d i s C i p l i n a r y r e s e a r C h Chapter 3 ABOUT The ÅlAnd ChUrChes prOject an important aim of the project was to employ systematic implementation of to put an end to all speculation about scientific methods of analysis on a large 14 the age of these significant churches. scale. This priority of the natural C analysis of fragmentarily preserved wood new approaches are needed this time. sciences has come as a surprise to Less well preserved wood, not datable through dendrochronology, such as fragments from wooden scaffolding or organic fragments embedded in the it is not enough to use traditional many art historians. scholars have even mortar, has systematically gone through radiocarbon analysis. Together with humanistic methods, instead the expressed concern that such an the results from dendrochronology, this material has provided an important churches themselves should provide approach might overshadow humanistic databank with age control for comparative research. the historical sources. archaeological aspects such as architecture, art history, artifacts and coins do not necessarily and style. yet interdisciplinarity and the date stone churches, as they can derive implementation of scientific methods in the pattern of the annual rings with the provide an exact date for the wood in from older buildings on the site, and fact often provide the very basis for pattern of the master curve individually question, but not necessarily for the they may also belong to later periods. archaeological, architectural and art developed for different geographical original building stage. Therefore, the The lack of written sources must be historical analyses. only with reliable regions, it is in principle possible to initial results were somewhat disappoint- compensated by all available methods. results is it possible to draw conclusions establish the exact year when the ing. all experts should be consulted. concerning the medieval history of the timber was felled. so far the method although dendrochronological now was finally the time to establish Åland islands, about the building has primarily been used for oak and analysis could not always determine the the true dates of the churches. To reach activity, and about the art of the pine. date for the first building stage of the an objective chronology, i was prepared churches. Thus dendrochronology was the first construction, the benefits of the ideally this chapter should function scientific method implemented by the implementation were soon evident. as a guide through the large numbers project, and all available timber in the dendrochronology could determine the of complicated scientific processes. Åland churches was tested. The analyses ages for secondary building stages, such above all through the different steps of were performed in 1991-1992 by as towers, vaults, porches, and sacris- developing mortar dating, which have Thomas bartholin, from the national ties, which meant that we had valuable been taken within the Åland Churches Museum of Copenhagen and the material for comparative analysis, and project. other methods used are also university of lund. of a total of 283 for the interpretation of an internal described, as is the interdisciplinary samples 159 yielded results, and out of building history of the churches. collaboration and the result of this these 107 were of medieval origin. This peter Tångeberg, the swedish approach. material was to form the basis for an conservator and art historian, was Åland master curve. however, a large consulted about the wooden sculptures Dendrochronology part of the samples were of spruce, a in Åland; he suggested that i should To begin with, everything seemed timber which is not easily dated by this contact peter Klein from the university straightforward and easy. dendrochro- method. often, it would also show that of hamburg, in order to complement nology was the method to solve all the annual rings were too few for a stylistic analysis with dendrochronologi- problems. it was to be implemented on determination of the age. cal dating of the sculptures. Klein has all the churches, on all building stages. it was also demonstrated that well developed an important non-destruc- of all scientific dating methods preserved timber mainly derived from tive method for wooden sculptures, dendrochronology is the most reliable. secondary building stages, or from later where a nailbrush and a loop replace The sample is drilled from the sapwood repairs. due to rot and fire, many parts the drilling into the wood. The analysis Fig. 167. Peter Klein analyzing a to the inner core, if possible with all of the roof constructions had been of individual wooden sculptures is wooden sculpture in Finström church, annual rings included. When comparing renewed. dendrochronology can described in their respective contexts. July 2005. 134 abouT The Åland ChurChes project diagram of aMs analysis final particle detector radiocarbon sample 12 13 14 Tandem accelerator 3 Mill. volt 12 ion source 13 14 Magnet argon analyzing magnet radiocarbon dating as a method radiocarbon dating (14C with the same number of protons (6 for 6000 years the organism contains only prepared graphite sample is placed in analysis) was developed at the end of carbon), but with different numbers of half of the original amount of 14C an ion source, after which the ionized the 1940s by Willard f. libby, who neutrons in the nucleus. There are three isotopes. furthermore, a beta particle is carbon isotopes pass through two received the nobel prize for this different naturally occurring carbon triggered for each decaying atom. angled magnets on each side of the discovery in 1960. in the atmosphere of isotopes: the 12C isotope, which in at the beginning, the measure- accelerator. already by the first magnet the earth, carbon exists primarily as addition to 6 protones includes 6 ments were done conventionally, by a number of 12C and 13C isotopes are carbon dioxide (Co2). in the inner neutrons (a total of 12 nuclear particles), beta counting, or measuring and thrown out of their course. The circulation of the carbon, carbon the 13C isotope with 7 neutrons, and detecting of beta emissions from 14C remaining isotopes (14C) reach the dioxide is bound to the earth through finally the 14C isotope which has 8 atoms over a period of time. Conven- tandem accelerator, which they pass the photosynthesis of plants. from the neutrons. by far the most common is tional dating requires large samples. with accelerated (hence the name) plants it is further spread to animals and the stable isotope 12C which represents one kilogram raw-material (mortar) is speed, only to force the remaining 12C to different living organisms in the food 98,9% of all carbon isotopes. The 13C needed to get the necessary amount of and 13C isotopes off course at the next chain. isotope, equally stable, amounts to 1-2 grams of pure carbon. since only magnet. Thus only the 14C isotopes The amount of 14C stored in plants 1.1%. Thus, together the two stable isotopes decaying during the period of reach the final detector, where every and animals, in the oceans and in the isotopes form about 100% of all carbon analysis are measured, the conventional single 14C isotope is counted: the fewer global carbon reserves, remains rather isotopes. unlike the other carbon method is less precise and the statistical the 14C isotopes that reach the final constant through the ages, which isotopes, however, the 14C isotope is uncertainty becomes larger for small particle detector, the older the sample. means that the 14C contents of living unstable, and is only a minimal part of samples. radiocarbon dating is a statistical organisms is largely the same as in the the entire whole. That is, only one of a for radiocarbon dating the introduc- method, with built in error margins atmosphere. radiocarbon dating is million millions carbon atoms is a 14C tion of accelerator mass spectrometry presented as ± values. based on the ratio between radioactive isotope. it is radioactive, and therefore (aMs) in 1977 meant considerable 14C and the stable isotope 12C, a relation characterized by radioactive decay, improvement. The system requires a that mirrors the atmospheric concentra- which starts when the living organism tandem accelerator, which includes two tion of the isotope in living organisms. dies. The decay has a half life of 5730 separate phases of acceleration. The isotopes of an element stand for atoms years, which means that after less than diagram demonstrates the process: the abouT The Åland ChurChes project 135 Calibration a basic fact concerning all 14C dated curve falls irregularly, which affects Church Churchof Jomala,tower of Jomala,tower LemböteL embötechapel chapel materials, not only mortar, is that the the precision of the results. Where combined calibrationcombined calibration combined calibrationcombined calibration result is presented as a BP (“before the curve is falling steeply, the margin 720±12BP 720±12BP 642±15BP 642±15BP present”) age. paradoxically “present” of error is only a few years, but where1000 BP 1000 BP 1000 BP 1000 BP in this case is identical to the year the curve is largely horizontal, or 900 BP 900 BP 900 BP 900 BP 1950, since after that the amount of when it wiggles and turns upwards, carbon dioxide was disturbed by the measurement becomes less 800 BP 800 BP 800 BP 800 BP repeated atomic tests and nuclear precise. for medieval scandinavia 700in BP 700 BP 700 BP 700 BP power stations. since the ratio of the general, and for medieval Åland 600 BP 600 BP 600 BP 600 BP isotopes in the carbonate of the especially, the irregularity during the sample reflects the carbon dioxide at 14th century is a greatly disturbing 500 BP 500 BP 500 BP 500 BP the time when the mortar hardened, factor.