What do you do if one of your 17th century deeds – a really big one, in three pieces, beautifully illustrated, with a seal attached – has become dirty and brittle over the years and is folded up so that it can barely be opened? You call in the Conservation Department, that’s what you do.
A few months back a 17th century parchment deed in poor condition came to the Conservation Department from the Manuscripts & Archives Research Library. The document is dated from 1666 and is a patent grant of lands in Ireland to Thomas Lestrange under the Acts of Settlement and Explanation
The challenge was to conserve the large format document (900 mm x 750 mm with seal) consisting of three parchment leaves, attached together at their bottom edge, which made handling and treatment difficult. Moreover, the large black wax seal was soiled and fragmented. The third leaf was beautifully illustrated with a portrait of Charles II of England, floral borders, lions, enchained unicorns and butterflies among others. Some of the pigments employed were brittle and in need of consolidation.
After dry cleaning each side with a soft Japanese brush, the deed was placed in a humidity chamber at 25° C and 90 % relative humidity for two hours.The leaves were then tensioned on a board with pegs and clips. This step is crucial since the fibres of the parchment are horizontally oriented which gives the parchment its mechanical and visual properties. Introduction of water or humidity can change that orientation and distort the parchment. Tensioning the hydrated parchment is essential to keep the fibres parallel to the surface. After two hours of tensioning, the deed was placed under weights for the night.
This first relaxation produced good results but the creasing on the illuminated leaf was more severe. It was humidified locally with a Gore-Tex® membrane and two damp blotters and tensioned again with pegs and clips again. This method enabled the conservators to relax one leaf at the time and the introduction of humidity was slow and controlled.
The large tear on the illuminated skin had opened out and the distance between the edges was about one centimetre running through the portrait of the king. A Gore-Tex® membrane was again employed, but this time only on the upper half of the parchment and for 20 minutes with a slightly damp blotter. Japanese paper bridges were quickly applied with wheat starch paste on either side of the tear and it was then put under weights. The parchment reacted very well and we were able to narrow the tear. The edges were still slightly open in some areas but it was decided not to attempt any further manipulation lest any additional stress in the parchment be created.
The large amount of tears were mended with caecum glued on the verso with 10 % isinglass glue, a substance obtained from the dried swim bladders of fish, dissolved in deionized water. The large losses were infilled with parchment on the recto and supported by caecum on the verso. We consolidated the pigments with a 1 % solution of isinglass under a microscope. A drop of isopropanol was applied just before the consolidant in order to reduce the surface tension of the adhesive and improve the penetration and spreading under the pigments.
A small and vulnerable piece of the wax seal came off during treatment. Isinglass was chosen as the adhesive, due to its good bonding properties and, being water soluble, it is thus reversible without damaging the wax substrate. It was applied to the detached piece with a brush, positioned and held in place for a few seconds. The attachment is strong and the repair is almost invisible
Housing was an important part of the project particularly as it had to meet the requirements of the both storage and scholarly access. The housing has to allow easy access to the large skins, protect the vulnerable wax seal and lightly restrain the parchment while in storage.
A box was designed in which the first document (the one at the back) is attached to a thick board platform with Mylar® corners and the bottom of the deed is secured with a strip of Mylar®. The two other leaves are not attached but they are retained when the box is closed by two substantial foam (Plastazote®) batons fixed to the inside of the lid.The platform can be remove from the box employing two fabric handles on each side.
The seal is secured with a card former and black foam (Plastazote®) filler for the missing areas. It is is placed on a thin layer of that same foam in order to support the significant relief on the back face. Three pieces of linen thread going through the platform and knotted on the verso secure the textile to the board.
A two months stay in the Conservation Lab made this large artefact easier to handle and much less vulnerable than before treatment. The object will be housed flat and the reader or researcher will be able to access the three leaves without removing the object from the platform.
This project was supervised and this blog co-written by senior conservator John Gillis.
Heritage Council Intern