Bottom heavy hazardOctober 17, 2012 About my museum job, Blogs, Conservation, Dissection and Resurrection Men
Following on from Jill Saunders’ recent blog, The main event, the closing post in the series on the conservation of the iron coffin from St Bride’s looks at fixing the final problem of supporting the coffin base. Come and see the coffin for yourself in our Doctors, Dissection and Resurrection Men exhibition opening on 19 October.
Our work on the coffin was nearly complete and we had stabilised a great deal of valuable material and discovered many things along the way. However, the object presented one final major problem to us in the heavy bottom sheet of the main coffin, which was only partly attached to the walls. This meant that whenever the object was lifted, the weight of this base was unsupported and pulled heavily on the attached regions. We felt this could eventually lead to the whole base falling out – which we obviously wanted to prevent. There were two main courses of actions to limit the risk of this undesirable occurrence; either we could find some way to adhere the base along the edges from which it had become detached (the suggested material was EPOPAST), or we could provide a simple base which the object would sit in (though not be permanently attached to) and upon which it could always be lifted. As is usually the case in conservation, there were interesting and worthy arguments for and against both treatment courses:
1. Adhering the base to the walls
- Could secure the base indefinitely
- Could be reversible if a release coating was applied first
- Would make the object as robust as possible in preparation for its future life of manoeuvring outside of museum conditions.
- Quite an interventive procedure, which could have issues with reversibility
- Practitioner inexperience in the proposed material raised competency issues. Limited time to complete treatment exasperated this issue
- If quite a large amount of fill/adhesion material was needed it could cause aesthetic disturbance.
2. Providing a carrying base (unattached)
- Would uphold the popular professional concept of ‘minimum intervention’
- Would support the base adequately if used properly
- Would prevent contact handling of the object.
- Could easily be separated from the object in the future or misused
- May interfere with future display requirements if secured and if unsecured the base would then be unsupported
- If secured, could cause damage where attached
- Would require further input from the technicians who we would depend upon to make it.
Unable to reach a decision, we decided that the best thing to do was to practice using the proposed material to test its manageability and properties (e.g. strength, adhesion, working time) and our ability to use it. The quantity needed would be key to our decision. We found some scrap modern iron which would provide a good test as its surface would be harder for the material to adhere to than our object. If it managed this we would be confident it could work. We had the iron cut into four pieces by our technicians so that we could test joining lacquered and un-lacquered pieces to test the release properties of the coating we had used i.e. if it had a detrimental effect on adhesion or if we would need to add more to ensure reversibility. We had to ‘double glove’ when mixing the two components of the material because of all the glass fibres it contains. The material comes in two components, one a putty and one more liquid which have to be mixed according to a specific ratio measured by weight. The hardening depends upon a reaction between the two components.
• We arranged two sets of iron sheets at c. 90° to one another with a gap in between in order to mimic the base and wall:
• After the two components of the material had been thoroughly mixed we filled the gaps and spread out a small amount on each ‘base’ piece to provide additional test information about adherence to the untreated and lacquered surfaces:
• We were pleasantly surprised to witness the strength of the material in the morning which had both good adhesion to the surface and easily carried the weight of the attached piece. We also felt that we could use even less than we had in our experiment to secure the base, limiting the aesthetic disturbance.
We proceeded to mix up a fresh batch to use on the object, this time adding powder pigment to help the material blend in (the green colour is the natural appearance of the product). As the base and walls had now been lacquered three times we did not need to add an additional release layer. We filled along the gaps and when the material had hardened we used a stiff brush to remove any glass fibres which were sticking out. We lacquered the filled areas to seal in any remaining loose fibres and reduce aesthetic contrasted with the object but decided not to blend them in any further (using paints) as it is commonly considered mote ethical in conservation not to completely hide new material.