The Royal Navy's first submarine launched in 1901 was salvaged from the seabed by the Museum in 1982. In 1993, after eleven years on open-air display at the Museum, it became apparent that chloride-sponsored corrosion was causing the rapid deterioration of the submarine. The Museum recognized that a sophisticated conservation package was needed if the vessel was to be preserved for the long term. The conservation process outlined below began in 1995 and was completed in June 2001
The corrosion of Holland I was particularly acute because the vessel had absorbed high levels of chloride during the 69 years spent as a wreck on the seabed. Chloride sponsored corrosion in iron and steel proceeds approximately five times the rate of corrosion where chloride levels are low. The Museum adopted the strategy of (1) reducing the chlorides levels of the vessel and therefore reducing the sensitivity of the submarine to air and water and (2) building an environmentally controlled gallery for the long term display of the vessel where moisture levels could be strictly controlled.
The methodology of chloride extraction was well established with respect to archaeological and marine artifacts, however the treatment of an historic object the size of Holland I (120 tons, 16.3 x 3.3 m) was a major innovation. A process typically carried out on the laboratory workbench had to be scaled up a thousand times. A major concern was that the process itself could damage the artifact. Experiments with active electrolysis to treat corroding objects had in some instances caused considerable damage. For Holland I the Museum adopted a passive soaking process that would take much longer but which carried less risk. The submarine spent five years soaking inside a purpose built glass fibre tank built around the vessel. In 2001 the chloride removal process was considered to be complete. Designs were now prepared for a purpose built environmentally controlled gallery in which to house the submarineAt the same time a plan was prepared by the Museum curator working in partnership with freelance museum conservator Ian Clark for the remedial conservation and display of the submarine.
The key points on innovation in regard to the conservation plan are as follows:
An example of the conservation approach is the hull of the submarine which has a rough weathered appearance and is no longer in a sea worthy condition. Conventional restoration would have seen the hull extensively filled, patched and painted - largely disguising the reality of its aged and corroded state. However the Museum chose to seal the hull with a wax finish frequently used by archaeological conservators in order to protect the surface of the submarine but also to show the true state of the metal - the wax is like a varnish or lacquer and clearly shows all the detailed ageing. No large twentieth century maritime artifact had been treated in this way before. Traditional restoration has until Holland I been the approach and in some cases this does not produce the best strategy for conservation. However some parts of the original paint were restored. The areas chosen had to be in exceptionally good condition so that the paint would look right and was done primarily in order to enhance visitors understanding of the submarine. For example internally operational submarines past and present are painted white so as to maximize the working light for the crew inside, so in about two thirds of the internal space of Holland I is painted white, but, where there was no real interpretation benefit we have used the wax sealant. Financial and commercial factors meant that the step-by-step preparation of the boat had to be fitted around the dynamics of the building construction work. This project therefore necessitated an exceptional amount of co-operation between the various parties in order that both building and submarine progressed according to schedule. By way of illustration the conservator had to apply a first class uncontaminated wax finish to the submarine hull in conditions where painters and plasterers were working on the building immediately surrounding the vessel.
The gallery building that now encloses Holland I is also a major part of what makes this project innovative and exceptional. As already stated above the long-term conservation depends on the maintenance of a dry air environment. We believe Holland I is probably unique in having both such a stringently controlled environment and such a high level of visitor access to the outside and inside of the vessel. Ramping allows wheelchair access right up to the main visitor hatch into the submarine. The visibility of the vessel for visitors inside the gallery is superb and includes access into the submarine. The building's enormous glass window means that visitors can step back from the building and appreciate in one panoramic view the lines of the submarine hull.
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