Consolidation of Friable Media in a Manuscript: Conservation Treatment of a 1476 Prayerbook

The book is bound in full calf over shaped wooden boards with two clasps on the fore-edge. (Figure 1) The catch plates on the upper cover are still present but the straps are missing. There are several symmetrical holes and indentations on the cover besides blind-tooled patterns, showing there were once four corner bosses and one central boss attached to each cover but are missing now. The book is housed in a cloth covered wrapper and slipcase.

The text block is written on very fine thin parchment in Lettre bâtarde with 21 long lines per page. The book was previously re-backed and the spine is rather inflexible, as the book hardly opens to 90 degrees. (Figure 2)

The parchment leaves are not completely flat and have multiple creases near the edges. Some leaves are yellowing and have multiple sooty deposits in the margins that require surface cleaning. (Figure 3) A gathering consisting of folio 2 to folio 9 is detached from the text block due to the broken sewing thread. During treatment it was sewn onto a Japanese paper hinge and the broken thread was threaded back into the center of the gathering and secured in place. Wheat starch paste was used to reattach the gathering to the text block using the Japanese paper hinge. (Figure 4)

There are three full-page miniatures and 31 illuminated initials including six historiated initials in this book. All of the miniatures and initials are illuminated with gold leaf and have painted decorations. (Figure 5, 6) The media condition of all the miniatures and initials is overall unstable, including multiple losses, cracks, flaking, and abrasions. (Figure 7)

Before treatment, a spot test was conducted under LEICA M80 microscope using Winsor & Newton Series 7 00 fine brush. (Figure 8) The dry brush was used to lightly touch gold and manuscript paints of each miniature and initial to understand the friability of media. All locations of each problem area were recorded and the consolidation would be based on this list . (Figure 9)

In order to hold the book while doing spot tests and consolidating, we created a cradle for strapping the book to the target page. Two layers of VIVAK plastic sheet were bent into an L shape, and double-sided tape was used to adhere the layers. We also attached a polyethylene strip to the vertical side of the VIVAK sheet for strapping the book. While setting the book in place, a sheet of paper would be placed between the parchment leaf and the polyethylene strip. During treatment, a piece of conservation board would be placed under the page to create a flat surface for consolidation. (Figure 10)

During the examination, we found out some of the reasons for the unstable media condition in this book. First is the deterioration of the original binding material, which caused the media to flake and become powdery. Another reason is the creating process of the initials. Some of them have stamped patterns on the gold which often made the media around them flake or crack. The usage of the book is another reason for the unstable condition. Most patterns painted along the edges of the book show abrasion due to handling and flipping pages. (Figure 11) The inflexible spine forcing the parchment leaves to bend considerably is also a reason for media flaking and losses. We are not rebinding the book as it appears to be in its original binding, but keeping the leaf to be treated flat became a big challenge throughout the treatment. With the pages bending while opening the book, the detached and fragile media layer would often slightly lift and was hard to settle down. Especially loose media around creases on parchment leaves (Figure 12) and on the pages in the middle of the text block when the book can hardly open to 70 degrees. (Figure 13)

However, the unstable condition of the media concerns not only gold leaf and manuscript paints, but often includes the ground layer under the gold leaf as well, sometimes having lifted off the parchment with the gold still firmly adhered to its surface. This layer is very brittle and prone to fracturing if even light pressure is applied. 

To understand the forces involved in the process of re-adhering large areas of a lifted, fragile layer of ground with gold, we made samples with parchment pieces and samples with a gilder's clay base, also called bole. (Figure 14) We attempted to create flat pieces of the bole which we then adhered to small pieces of parchment using different consolidants. We started with adhering one edge, and then used ethanol followed by the consolidant in repeated applications to aid in the wicking of the consolidant under the lifted bole. We examined distortion and stiffness of air dried samples and also investigated weighting them down as they dried. The resulting distortion of the parchment was deemed too much, so we abandoned attempting to re-adhere large areas of lifted ground with leaf gold.

After a series of tests with various consolidants and concentrations, isinglass with deionized water was chosen as the suitable consolidant for the paint. For the flaking ground layer, fish gelatin was used because of its stronger adhesion.

To apply the minimum amount of consolidant in the right spot, consolidation was conducted with a Winsor & Newton Series 7 00 fine brush under a LEICA M80 microscope. (Figure 15) Another fine brush was used to apply ethanol first to let the consolidant flow easily under the unstable media. For lifted or flaking ground layers under gold leaf, sometimes dry fine brush or absorbent paper points were used to apply  light pressure or hold the loose pieces while the consolidant is drying. The absorbent paper point was also used to absorb excess consolidant. (Note 3) (Figure 16)

The full-page miniature between folio 161 and folio 164 was in the most unstable condition. (Figure 17) The ground layer under gold leaf has large areas of losses, leaving the parchment exposed. (Figure 18) Not only the edges along the losses are fragile, but the upper part of the miniature has a large area of tenting, for which the ground layer is lifted from parchment. (Figure 19) While consolidating a small loss on the upper left corner, we discovered the lifted layer would crack when the consolidant flows under because of its brittleness and detachment from the curved parchment leaf. After researching different conservation techniques and consulting with various conservators, we decided not to conduct an overall consolidation treatment on the lifted area to avoid potential fractured gold. While retaining the tight binding structure, it would be hard to settle all the lifted layers onto a curved surface without creating cracks. As a result, we only secured the loosening pieces and some of the edges along the loss. (Figure 20) To prevent further damage, we suggest the book should be carefully handled and the page of this miniature should not be opened too wide during usage.

Consolidation is a conservation treatment that secures fragile media onto the support. There are many factors to consider before treatment. Including the condition, the material of media and support, possibility of visual alteration, characteristics of the consolidant and handling expectations etc. In this case, we conducted the treatment locally with a fine brush under the microscope, hoping to enhance the stability of the media without severely changing the appearance. (Figure 21, 22, 23. Tone might be slightly different due to different photography methods.)