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The conservation of Wimborne St Giles parchment map

Our Conservator has just completed the conservation of a large parchment map belonging to the Shaftesbury Estate. Here she describes the challenges of working with this complex material.

As the Conservator at Dorset History Centre, I have the privilege of working on some fascinating and intricate documents, and in 2015 my skills were tested when I was asked to conserve a large scale parchment map of Wimborne St Giles from 1659.  The hand-drawn, colour map shows field systems and land ownership in mid-17th Century Wimborne St. Giles and provides details of the topographical and agricultural features of the day.  It is significant because relatively few maps from this period have survived and it forms part of a very small number of its kind which can inform us of continuity and change in our landscapes. 

The challenge of parchment

The map consists of six parchment skins.  The adhesive holding them together had long since failed and some attempt had been made to keep the skins together by sewing along the joints.  However, this too was coming apart and the map arrived in 3 sections, unwieldy and cockled from previous exposure to high humidity.  If parchment becomes too damp it tries to revert to its original animal form and each of the six skins had reacted differently to this exposure.  As such the drawing on the map no longer aligned when the skins were placed next to each other.

A long-term treatment

Each skin was cleaned with a soft goat hair brush and latex sponge. Small tears in the parchment were repaired using cold gelatine mousse as an adhesive.  Then the six skins were re-attached in small sections at a time.  Where the skins had shrunk or expanded and no longer aligned, localised humidification was used to gently manipulate the skins back into position.  This process took several weeks due to the size of the map and allowing the skins time to 'acclimatise' to being re-adhered and relax to their original positions.

Once all the skins were in place, the whole map was slowly humidified and bulldog clips, padded with foam and attached to the edge of the map, were pinned to a board, holding the map under tension whilst it dried.  This technique is a replica of that used to make parchment.  Once dry to the touch, the clips were removed and the map was placed between felts and dried under weights for a further six weeks to ensure it was completely dry.

Future protection

A bespoke box was created from archival box board for storage.  The map is rolled onto a tube and the box has two supports either end to suspend the tube.  This prevents excessive weight being placed on any section of the parchment.  The map will return to St Giles House, home of Lord Shaftesbury, who funded the conservation work.  Preservation of the archive is part of a wider restoration programme being undertaken at St Giles House by the 12th Earl.

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