News & Timeline

Lemland anonym apostel, kalkmaln


Presentations and participation in International conferences:


During the coming year the network aims at presenting the results from the project “Intercomparison”, a system where different types of mortars are prepared and analyzed following different proceedings. This part of the project was initiated at the workshop in Mallorca 2012 with the aim to decide what type of preparatory method and analysis is best suited for different types of mortar.

June 27 – July 1 2016, at The 8th 14C and Archaeology conference, in Edinburgh, the network will present the results of the above mentioned Intercomparison project. Further, at this conference a special session is planned for mortar dating.

October 10-12 at The 4th Historic Mortars Conference in Santorini, Greece the network will participate with the following presentations:

Roald Hayen et al., Absolute Dating of Mortars – Methodologies Compared.

Mark Van Strydonck, A Historic Overview of the Method of Mortar Dating.


In September the network met for The 4th International Mortar Dating Workshop, in Zürich, ETH Hönggerberg – Science city Zürich. Organizer Irka Hajdas.

The topic of the workshop was Intercomparison and Age and Antrhopogenic Carbonates: Radiocarbon Dating of Mortars. Limes and Stucco.

Among others the following presentation:

Å. Ringbom, A. Lindroos and Jan Heinemeier, Lime lumps analyzed since April 2014 (Padova).


The network for mortar dating is rapidly growing. At the moment we count research groups in Italy, Spain, Portugal, The United States, Belgium, England, Switzerland, Slovakia, Israel, Poland, Sweden and Finland.

January 2-5, at the Archaeological Institute of America, (AIA) the Annual Meeting in Chicago Åsa Ringbom and John R. Hale presented a poster with the title:

Recent Advances in Radiocarbon Dating of Ancient Roman Mortar and Concrete.
Poster Chicago 2014

the Third International Mortar Dating Workshop, Padova 2014

April 14-16 Our team Åsa Ringbom, Alf Lindroos and Jan Heinemeier participated actively in the Third International Mortar Dating Workshop, in Padova, Italy, with several presentations:  Ringbom, Å. Keynote lecture, abstract (The Story of Mortar Dating, from an Archaeological Point of View).



11-13 of September Åsa Ringbom participated in  ”The 3rd Historic Mortars Conference”, Glasgow, with the following presentation:

The International Mortar Dating Project – Promising Advances with Dating Lime Lumps Embedded in the Mortar


8-12 of April  Åsa Ringbom and Alf Lindroos participated with two different presentations in The Seventh 14C and Archaeology conference, in Ghent, Belgium, where one entire section was devoted to mortar dating.:


Ghent 2013 mortar group.

Ghent 2013, members of the mortar dating group

9 of April, Åsa Ringbom (together with Alf Lindroos, Jan Heinemeier, Pia Sonck-Koota) presented:

Nineteen years of mortar dating – learning from experience. The International Mortar Dating project 1994 – .

9 of April, Alf Lindroos (together with Jan Heinemeier, Åsa Ringbom och Gregory Hodgins) presented:

Tracing contaminants in the AMS mortar dating process and elimination by sequential dissolution.

7-8 of Februari Alf Lindroos participated in The AMMC Conference on Ancient and Modern Mortars in Florence, the conference was arranged by the Associazione Italiana Archeometria – Italian Association of Archaeometry and the Forum Italiano Calce – Italian Building Lime Forum. Lindroos presented the Key Note Lecture:

”Lime Mortars as a Material for 14C Dating”.


Presentations and participation in international conferences:

February 4, Åsa Ringbom presented:  Åländska skärgårdskyrkor i sten – Föglö, Kumlinge, Kökar, at the BOTTNISK KONTAKT XVI  (Bothnian contacts) seminar in Korpoström, Korpo, Finland,  3-5. februari 2012. The topic of the seminar was contacts and/or conflicts.

August 27 . 30, Åsa Ringbom took part in the 23rd Nordic Iconographic Symposium in Saeby, Jutland. She presented the following paper: ”Liturgical Drama in Parish Churches?”

August 29-September 2 Alf Lindroos and Åsa Ringbom participated at the Medieval Europe conference arranged jointly with the 18th symposium for the European Archaeological Association (EAA) in Helsinki, with a presentation ”Lime Lumps as a Material for Mortar Dating”. Alf Lindroos presented the paper.


September 17-21. The research team was invited to participate in The Second International Mortar Dating Workshop, Mallorca. Organizer: Mark Van Strydonck. Kikirpa, Royal Institute for Cultural Heritage, Brussels. Mallorca program & abstracts

The participants of the Mallorca Workshop. From the left: Greg Hodgins, Roald Hayen, Mark Van Strydonck, Vincent Debonnes, Irka Hajdar, (hidden behind her Guy De Mulder), Alf Lindroos, Tess Van den Brande, Jan Heinemeier, Jose Palmer Comas, Åsa Ringbom, Bob Hohlfelder, Kathryn Barth, Fabio Marzaioli, Damia Ramis, Magdalena Salas and Dolors Domeniquez Henares.

September 24, Åsa Ringbom guided the participants of the ”Swedish History Days” to the churches of Finström and Sund.

During 2012 the following publication will emerge: Lindroos, Alf, Åsa Ringbom, Jan Heinemeier, Gregory Hodgins, Fiona Brock, Lior Regev, 14C dating of fire damaged mortars from medieval Finland, Radiocarbon 2012.

For further information concerning the mortar dating project and its international network, see



The International Mortar Dating project sponsored by the Finnish Academy came to an end, but it still continues as different externally financed projects, among others the dating of the Gotland churches. Åsa Ringbom frequently acted as a guide to the Åland churches, among those participating can be mentioned former Swedish Prime minister Göran Persson and his wife Anitra Steen.

Göran Persson, Anitra Steen and Ingrid Iremark in Finström church,  August 2011.

April 10-15. The research team participated in the Radiocarbon & Archeology 6th International Symposium, Cyprus, April 10-15, 2011. At this symposium mortar dating was presented in four different posters. In addition to our contribution mortar dating was presented in posters from Rome, Switzerland and Jordan.

Our poster: Lindroos et al. Cyprus_poster
Alf Lindroos, Åsa Ringbom, Jan Heinemeier, Gregory Hodgins, Fiona Brock, Lior Regev, 14C dating of fire damaged mortars from medieval Finland.

October 4, press release for  ”The Voice of the Åland Churches. New Light on Medieval Art, Architecture and History”, by Åsa Ringbom. The book is a translation from  ”Åländska kyrkor berättar. Nytt ljus på medeltida konst, arkitektur och historia” published in 2010.


September 30 Åsa Ringbom retired from her chair as research professor at the Åland University of Applied Sciences and Art History, Åbo Akademi. This means that she now can devote all her time to continued research on the Åland churches and different international projects.

June 8 – 12, the research team participated in the Archaeology and History of Churches in the Baltic Region, Symposium, Visby, Gotland (Åsa Ringbom, Pia Sjöberg och Alf Lindroos). See publications 2011.

August 9 – 15, the International mortar dating project hosted the first International Mortar Dating Workshop, in Finland (Åbo/Turku, Åboland and the Åland Islands). Organizers: Åsa Ringbom, Alf Lindroos, Pia Sjöberg and Pia Sonck-Koota. Click here to see the program. First International Mortar Dating Workshop program

This first International Mortar Dating Workshop resulted, among other things, in the following homepage:


Mortar Dating Workshop; Kökar, Åland, some of the participants prepared for swimming.


May 28 – June 5, Åsa Ringbom and Jan Heinemeier participated with a presentation on mortar dating and the Åland churches in the 20th International Radiocarbon Conference, Hawaii. (See publications 2010).

Arny Sveinbjörnsdottir, Jan Heinemeier and Åsa Ringbom at the 20th Radiocarbon Conference, Hawaii

June 4, Successful AMS 14C dating of non-hydraulic lime mortars from the medieval churches of the Åland Islands. Arr. The 20th International Radiocarbon Conference, Hawaii, Big Island. Jan Heinemeier and Åsa Ringbom.

October 1-2, Alf Lindroos and Åsa Ringbom presented current research at the Nordiskt forum för byggnadskalk, Kalmar, Sweden.

October 20, Why mortar dating? Research Seminar. Art History, Åbo Akademi, ÅR.


January 3-6, the research team (Åsa Ringbom, Alf Lindroos, Jan Heinemeier, John Hale, Lynne Lancaster, Fiona Brock) participated in the Annual Meeting in Chicago, the Archaeological Institute of America, with the poster ”Mortar Dating in Classical Archaeology”.

Click on the poster for a readable PDF file.

Our Chicago poster was awarded the following prize: “Judges Choice – Best Poster”.
January 6, Presentation by Åsa Ringbom at the Archaeological Institute of America, Annual meeting in Chicago, ”Radiocarbon Mortar dating at Torre de Palma, a case study from the margins of the Roman Empire 1997-2000”.

March 27-29, Together with professor Robert Hohlfelder, Colorado University, Boulder, Åsa Ringbom arranged the symposium ”Building Roma Aeterna” in Rome. The American Academy in Rome, The British School in Rome, and the Institutum Romanum Finlandiae (Villa Lante) jointly hosted the occasion.
At this symposium mortar dating was presented by different members of our team. See publications 2011.

October 15 the Mortar dating project was presented ”Dating the Roman Empire and Beyond: Understanding the Methodologies and Applications for 14C Mortar Dating” at Museu Nacional de Arquelogia, Lisbon. The audience was The Archeological Institute of America and the Iberian Peninsula Society, Speakers: Åsa Ringbom, Jan Heinemeier, Alf Lindroos, from the Scandinavian Mortar Dating Team.

14-16 oktober, Workshop på Museu Nacional de Arquelogia, Lissabon. Deltagare: Stephanie Maloney, Maia M. Langley, Åsa Ringbom, Jan Heinemeier, Alf Lindroos.


The parallel project International Mortar Dating was initiated. The PhD students Pia Sjöberg och Pia Sonck-Koota joined the research team.

PhD student at Åbo Akademi University: Pia Sjöberg, Art History, and Pia Sonck Koota, Geology and Mineralogy.

June 8, Presentation at the ” 9. Kirkearkaeologiske Symposium, Kalundborg 7-10 juni 2007,  Projekten Ålands kyrkor och internationell murbruksdatering, – en lägesrapport. Åsa Ringbom, Jan Heinemeier och Alf Lindroos, (see publications 2010)


Collaboration with the Gotland churches was initiated (Heikki Ranta och Joakim Hansson).

Bro church, Gotland, mortar sampling team in September 2006, from the left: Otto Andersson, Joakim Hansson, Heikki Ranta and Alf Lindroos.

Collaboration initiated with the NSF Arizona Accelerator Mass Spectrometry Laboratory, University of Arizona.

March 30, Cambridge, “Mortar Dating in Classical and Medieval Archeology, Second International Conference on Construction History, Queen’s College, March 29-April 2, 2006. Åsa Ringbom (see publications).

April 4, Oxford, 19th International Radiocarbon Conference, AMS mortar dating in Medieval and Classical Archaeology – a decade of development and testing. Keble College, Oxford. April 3-7, 2006, Jan Heinemeier.

June 12-15 ”The C-14 Ancient Mortar Project: An Interdisciplinary collaboration to develop techniques for AMS dating of concrete and other lime mortar construction materials”. Planning meeting for the international research team (Jan Heinemeier, Alf Lindroos, Pia Sonck-Koota, Fiona Brock, John Hale, Åsa Ringbom) Bartsgårda, Åland.


Collaboration initiated with the Oxford Radiocarbon Accelerator Unit. The mortar dating team visited the Oxford laboratory, Alf Lindroos, Jan Heinemeier, John R. Hale and Åsa Ringbom.

March 10, Presentation of the International Mortar Dating Project, The Oxford Radiocarbon Accelerator Unit, Oxford, UK, ÅR.

March 17, Presentation of The International Mortar Dating Project, arr. Italcementi, Bergamo, Italy. Åsa Ringbom and Alf Lindroos.

In the summer of 2005 Peter Klein conducted archeological analysis of the wooden sculptures in the Åland churches. Peter Tångeberg gave his expert opinion on the sculptures, his suggested dates later proved to be precise and identical to the results from dendrochronology.


June 10-14,  “New light on cultural contacts in Medieval Åland”, IIIrd European Congress of Medieval Studies.
Jyväskylä, Finland, ÅR.

August 23-26, Åsa Ringbom, Alf Lindroos, Lynne Lancaster, John Hale and Jan Heinemeier; When did the mortar harden? A new method of dating buildings and other structures through AMS radiocarbon analyis, Poster Session. XVI International Congress of Classical Archaeology of the Associazione Internazionale di Archeologia Classica (AIAC) Harvard University, Art Museum, Boston/Cambridge USA.


”The Harvard poster”. Click the poster for a readable PDF file.

The research team at Harvard 2003: from the left John R. Hale, Åsa Ringbom, Jan Heinemeier, Lynne Lancaster and Alf Lindroos.


Marked the end of the participation of the research team in the excavations at Torre de Palma, Vaiamonte, Portugal.

The interdisciplinary team at Torre de Palma, from the left:  John R. Hale, Jan Heinemeier, Åsa Ringbom, Stephanie Maloney, Alf Lindroos.

September 16 , Åsa Ringbom presented ”Mortar dating, a presentation of the method” at the European Association of Archaeology, Conference, Lisbon.

June, Åsa Ringbom presented ”Mortar dating – a method with a potential for the future” at the Second International Conference of Medieval Studies, Barcelona.


Lynne Lancaster

Collaboration on mortar dating in Rome together with was initiated Lynne C. Lancaster, Classical Archaeology, Ohio University, Athens, OH.

October 19, Different views on church research examples from the Åland Islands, presentation by Åsa Ringbom at the department of Art History, Tromsö University, Norway.


Participation of the research team in archaeological excavations were initiated at Torre de Palma, Vaiamonte, Portugal.

The sponsoring from the Academy of Finland was ended, and the project was taken over by the University of Applied Sciences, Åland.

December 27-29 Åsa Ringbom and John R. Hale participated at the The Annual Meeting of the Archeological Institute of America, i Chicago, where John R. Hale presented mortar dating in the Åland Islands.

John R. Hale


During the fall semester Åsa Ringbom chaired the F.L. Morgan chair in Architectural History at the University of Louisville, Kentucky, which resulted in a long-term research collaboration with the archaeologists  Stephanie Maloney and John R. Hale. This also meant the implementation of  mortar dating into Classical Archaeology.


The interdisciplinary team sampling mortar in the church of Jomala, Åland. From the left: Kenneth Gustavsson, Jan Heinemeier, Högne Jungner, Åsa Ringbom, Thorborg von Konow and Alf Lindroos.

The project moved over to the use of AMS 14C in mortar analysis. All earlier results from conventional dating were nullified. This meant the beginning of the most important collaboration with Jan Heinemeier at the 14C  AMS Dating Centre at the University of Århus. At the same time Alf Lindroos, geologist at Åbo Akademi University joined the team. Since then he has been responsible for the scientific development of the mortar dating method.

Jan Heinemeier and Alf Lindroos


All the Åland churches went through dendrochronological analysis, conducted by Thomas Bartholin, the University of Lund.


The Åland churches project was initiated, sponsored by the Academy of Finland.


In August, at a Franciscus conference at Källskär, Kökar, Högne Jungner at the Laboratory of Radioactive Dating at Helsinki University, presented the mortar dating method. At the same time the first interdisciplinary research team was formed, consisting of Högne Jungner, Kenneth Gustavsson, Milton Nunez and Åsa Ringbom. A pilot project started, financed by the Academy of Finland.


The ideal environment for interdisciplinary research. Several years before the Åland churches project was on the agenda, contacts had been made across the faculty borders at Åbo Akademi University. Geologists and art historians regularly shared morning coffee at Gadolinia, Second from the left Alf Lindroos, Åsa Ringbom, Bo Lindberg and Nils Edelman.