Open studio event at LMA – Behind the Scenes in Conservation

Next Tuesday 20th November we will have an open studio day. This is an opportunity to come and see the repaired and housed Great Parchment Book. Rachael will show you the techniques she has used to humidify, tension dry and repaired the parchment.

Just come to London Metropolitan Archives between 10 and 12 or 14 and 16. To find out more please click here.
See you soon!

Great Parchment Book membranes

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Repackaging

Once all the sheets had been treated, they just needed rehousing. The sheets could not be put back into their original boxes because they were no longer suitable in terms of their size and shape. Also, it was felt that the boxes were housing too many sheets to a box.

For ease of handling, it was decided that the sheets should be stored in Clamshell style boxes with, on average, six to a box. The sheets would also need to be interleaved to stop them catching on each other. The interleaving material needed to be something thin and flexible that would mould to the shape of the sheets, so reducing the risk of extra bulk, but also smooth surfaced so the sheets won’t catch on it. It will also act as a support for each sheet when moving them in and out of the boxes.

Tyvek® was chosen for the job as it fits all these qualities and is chemically inert.

Lifting the membranes

Repackaged

Repairing the membranes

There are fragments from some of the sheets that have been found at the bottom of the boxes. Some of these have already been matched up to certain sheets and numbered; some still need to be matched up. Gelatine coated tissue is used to hold these loose fragments in place.

Attaching gelatine coated tissue splints

Attaching gelatine coated tissue splints

TREATMENT on the Great Parchment Book

Part 3

Tension drying

Magnet drying is proving to be the most effective method for holding out the creases whilst drying. Metal sheets are wrapped in thin blotter and covered with thin non-woven polyester (which reduces the risk of the parchment sticking). Magnets wrapped in felt or Tyvek® are used to hold open creases whilst the parchment dries. It was found fairly early on that the amount of shrinking present on some of the sheets was preventing the creases from being pulled out horizontally. This was remedied by inserting polyester wadding underneath the creased area and so pushing it out in a vertical direction, as well as pulling horizontally with the magnets.

The edges of the parchment are held down with magnets

The edges of the parchment are held down with magnets

Tears can also be secured with magnets

Tears can also be secured with magnets

TREATMENT on the Great Parchment Book

Part 2

Testing of inks

Prior to humidification, the Inks were tested for solubility in water and also for the presence of any metals within the ink. The inks were found non-soluble in water and, for the most part, no presence of metals was detected.

Humidification

The sheets of parchment are placed in a humidification ‘sandwich’, where they are layered up with Gore-Tex® and damp blotter (see diagram below) and left to gently humidify for approximately six hours.

Cross section of humidification set-up

Cross section of humidification set-up

Small ‘humidity packs’, made by wrapping Laponite® (a synthetic layered silicate) in thin non-woven polyester and then Tyvek® (a brand of flash spun high-density polyethylene fibres), can be placed in the sandwich over the shrunken areas to increase the humidity reaching these areas and therefore increase the softening.

Humidity packs placed over shrunken areas

Humidity packs placed over shrunken areas

TREATMENT on the Great Parchment Book

Part 1

With all the tests we have carried out we are now ready to start to work on the Great Parchment Book!

Surface cleaning

Prior to humidification surface cleaning is being carried out using vulcanised rubber sponges and soft goat hair brushes. The sponge works by picking up and drawing in the dirt when it is placed in contact with the surface of the object to be cleaned. With the Great Parchment Book, ideally, we would like to remove as much surface dirt as possible from the parchment to stop it being drawn into the substrate when it absorbs moisture during humidification. Also, it helps to improve the legibility of the text. However, where flaky media is present, surface cleaning has to be avoided as the sponge will pick this up too.

Area before cleaning

Area before cleaning


Area after cleaning

Area after cleaning

The ink on the sample above is very stable and so the area could be cleaned. The sponge was most effective on the area in the middle, where the dirt was sitting loosely on the surface. However, the dirt in the bottom right hand corner of this image was much more ingrained, and so surface cleaning did not improve it.

Treatment trials continued… (part IV)

17th-century samples with original fire damage

An original sample of heat damaged parchment (not part of the LMA collection) was found, and the magnet drying system was tested again. This was a good sample to test the treatment on as it had similar planar distortions and fragile edges as seen on the Great Parchment Book, which would not withstand having clips attached. (The sample was fully humidified between blotter and Gore-Tex®.)

Before treatment

Before

After treatment

After

Close-up before

Close-up before

Close-up after

Close-up after

Results

This method worked really well. Stronger, larger magnets were used around the shrunken areas to help hold the creases open, and then weaker, smaller ones were used to hold down the torn, fragile edges. However some tears, that were already present, did become wider and more obvious. This was a natural reaction to the overall plane of the parchment becoming flatter, but should be avoided when treating the Great Parchment Book.

Virtual flattening

Alongside all the conventional conservation work happening on the book, here at UCL we are experimenting with ways to “virtually restore” the book using a mix of imaging, computer vision, and computer graphics techniques.

Our approach is two-fold. First create a virtual 3D model of each page, and second flatten the 3D model into a 2D plane. It sounds fairly simple but is deceptively complex.

Creating detailed models of the pages requires a careful imaging process to try to get inside every crease and fold and capture every letter at as high a resolution as possible. The result is a set of 50 or so high-resolution images (for each page of the book). These are fed into a pipeline of computer programmes which (after a considerable amount of processing time) generates the 3D model.

Before flattening

Before virtual flattening

3D mesh

3D mesh

Then comes the problem of flattening the page in a sensible way. At first glance, it would seem that we want to just “unfold” the page as you would a crumpled piece of paper. However, the way the pages are distorted is not like crumpling a piece of paper and so there is no nice and easy way to “unfold” them. So now the problem becomes “how can we flatten the page into a 2D plane in such a way that the text does not become distorted”, and that is what we are trying to solve at the moment.

After flattening

After virtual flattening

Treatment trials continued… (part III)

RESULTS – PEGGING

Before treatment

Before

Suction table drying

Peg drying

After treatment

After

The peg method was quite successful in reducing the planar distortion on the fully humidified sample. The pins were put straight through the ends of the pegs, meaning the parchment was held very taught with not much room for movement. If using this method on the Great Parchment Book, which is much more fragile, we would want to allow for more movement to prevent tearing. Therefore elastic bands would be attached to the pegs and the pins put through these to allow for more flexibility.

Close-up before

Close-up before

Close-up after

Close-up after

Treatment trials continued… (part II)

RESULTS – SUCTION TABLE

Before treatment

Before

Suction table drying

Suction table drying

After treatment

After

It was found that with both local and complete humidification, suction table drying was not appropriate. It did flatten out the sheet, but pulled smaller creases in more deeply. This method would be more effective on items that were less badly damaged, without shrunken areas, and that could be humidified to a greater extent.

Close-up before

Close-up before

Close-up after

Close-up after