CONSERVATION OF THE SWEDISH WARSHIP VASA FROM 1628 Birgitta Håfors CONSERVATION OF THE SWEDISH WARSHIP VASA FROM 1628 Birgitta Håfors 2nd edition 2010 Copyright 2001 by the Vasa Museum, Stockholm, Sweden and Birgitta Håfors. Printed in Sweden ISBN 91-85268-86-0 Front Cover Photo: from the Archive of the Swedish National Maritime Museums Back Cover Photo: Hans Hammarskiöld Preface to the 2nd Edition In the beginning of the sixties, conservation of waterlogged archaeological wood became an important topic in the museum world. The Swedish warship Vasa was salvaged in 1961 and a few years later, two other archaeological large-scale wet site projects were started, namely the excavation of the Danish Viking ships at Skuldelev and the the medeival cog in Bremen. The testing and development of conservation strategies and practical procedures was a largely unexplored field at the time, and the intense work in the sixties, seventies and eighties by the conservators at the Vasa museum became of seminal importance for the preservation of Vasa, as well as other water-logged artefacts. Birgitta Håfors has been a key person in this work since 1961, and she summarized the work in the comprehensive report from 2001 on the conservation of the Vasa hull and the several thousands of loose objects. Since then, she has continued work with this material, in particular the role of the conservation agent, polyethylene glycol (PEG), in the preservation process. Since the publication of the first edition in 2001, continued preservation work and front-line international research on the chemical and mechanical changes occurring in the wood of Vasa has been pursued by the Museum in co-operation with national and international institutions and laboratories. A prerequisite for a successful work in this field is detailed documentation on all actions taken during the earlier stages of the preservation. It is therefore a great pleasure for SMM to publish the present updated second edition of Håfors’ report, which will be of great use for the continued efforts to preserve the Vasa and other large water-logged artefacts. The Museum is very grateful for her enthusiastic and dedicated work to complete this documentation. Stockholm, August 2010 Marika Hedin Lars Ivar Elding Director¸ Vasa museum Scientific co-ordinator Preface The preservation of the Swedish warship Vasa from 1628 is the largest undertaking of its kind in history. A large, black, waterlogged wreck has been transformed into a preserved museum piece of world renown, the centrepiece of the most visited museum in Scandinavia. The road covered in the process has been difficult and at times bumpy. In 1960, no museum had ever preserved a waterlogged wooden object of anything near the size of the Vasa. New methods had to be drawn up, tested and applied, while experts put forward their opinions, which were not infrequently diverging. As was often the case during the Vasa adventure, problems were solved by a combination of professional knowledge, commonsense and daring feats of imaginative thought. At no time was the going rougher than during the prolonged discussions in the 1970’s about when to stop spraying the hull with polyethylene glycol (PEG). The decision to discontinue the treatment was appealed against to the Government and eventually led to the resignation of the then head of conservation. The Vasa Museum is now pleased to present this documentation of the preservation of the Vasa. This book focuses on the preservation of the hull and covers the period from the raising in 1961, via the PEG treatment in the temporary Wasavarvet Museum from 1962 to 1979, the subsequent slow drying period, and the transport to the permanent museum in 1988, to the accommodation of the vessel in the new premises in the early 1990’s. We believe that this documentation will be useful for museum colleagues working with large waterlogged wooden objects, and we also hope that it will be an interesting case for science or museum studies. For its achievement in preserving the Vasa, the Museum is profoundly grateful to the conservation staff, a small but dedicated group of professionals, working in sometimes very difficult circumstances. In particular I should like to mention the late Mr Lars Barkman, M.Sc., head of conservation in the pioneering years from 1961 to 1978. The contribution of the Board of Conservation Specialists (Konserveringsrådet) with the voluntary participation of the foremost experts in fields such as wood chemistry and technology, polymer technology, ventilation and naval architecture has been (and continues to be) crucial for a successful preservation project. This is also shown by the many references to the activities and opinions of the Board in the present work. Finally, I should like to thank the author of this documentation, Mrs Birgitta Håfors, M.Sc.. She has participated in the preservation of the Vasa since the early days of the project, first as a chemist, and from 1978 to 1995 as head of conservation. During this long period, she has acquired an immense knowledge about the preservation of the Vasa material and of the history of the preservation project. No person could be more suited than she to pass on that experience to future generations. Stockholm, January 2001 Klas Helmerson Director, Vasa Museum INTRODUCTION The Commission At the meeting of the specialist board for the conservation of the Vasa on 6 February 1976, the member Ernst Abramson drew attention to the large number of documents that was accumulating during the work with the conservation of the Vasa. He pointed out the desirability of arranging and working on those documents so that they could be of use to other institutions in the same field. The same issue was again raised on 5 August 1977. This time the meeting recommended that the museum director as soon as possible should see that the documentation of what had up till then been done regarding conservation measures was started. The next time the question of the documentation of the conservation work was raised was on 16 October 1978 when the museum director informed the meeting of specialists that Lars Barkman, after seventeen years as head of conservation of the Vasa project, had resigned from his position. The meeting expressed great concern regarding the danger of delay in the documentation work that this might lead to. The specialists, did not however, give up the subject. At the meeting on 21 March 1979, a memorandum by Abramson was discussed. This described how the documentation should be carried out, and the meeting also recommended that a suitable member of the conservation staff should be charged with the task of executing the commission. This time, the museum director presented the matter to the board of the museum. On 15 May 1979, the Board of the National Maritime Museum decided that three aspects of the Vasa project were to be documented. The first was the history of the Vasa project from 1956 to 1964. The second was the conservation of the Vasa and the third was the restoration of the ship. The three commissions, in the order mentioned, were entrusted to Gillis Claus, myself and Lars-Åke Kvarning. At that time I had been working with the Vasa project for nearly eighteen years. The Planning The conservation project, however, needed much attention at that time, and this affected the documentation project. The work was started on a small scale and it remained on the agenda at the specialist meetings. First a schedule of reports on the conservation treatments of all categories of material that were represented in the Vasa project was prepared. The main subject was however the treatment of the Vasa hull and the large disconnected wooden finds. Because a chronological report was suggested in the discussions of the meetings of the specialists, I made out a plan with the Vasa hull as central object. The chronology of measures taken to carry through the process of preserving and drying the hull and the monitoring work involved was chosen as the backbone of the report. The disconnected constructional timbers and sculptural adornments that were treated in tanks would get their own chapters. The research work that had been my original task on the Vasa project would be the subject of a separate report. The Documentation Work In 1985, the conservation project had reached a stage that would allow some time to be devoted to the documentation report. To obtain some idea of what working method would be adequate, I was asked first to write a report on the work of developing the method of treating and mounting the Vasa sails as a smaller assignment. That report was finished in March 1985. I then started work on the main documentation report. To help exclusively with this, I was given one assistant for the registration of the archive material and one assistant to systematize the large amounts of measurement data from the monitoring activities. The work continued until the task of managing the actual conservation situation for the Vasa in the permanent Vasa museum demanded our full attention. The Report In 1995, it was decided that the documentation report would be put into focus again as my main task for a period of three years. The matter was brought to the attention of the group of specialists who, with old and new members, still remained at the disposal of the Vasa museum. The specialists have all shown great interest in the documentation work and have provided many useful suggestions. However, the report unfortunately had to be reduced to the backbone of measures regarding the hull, as being the most spectacular and demanding task of the Vasa conservation project. This means that there will be other reports concerning other aspects of this project.