In a sticky situation: the removal of pressure-sensitive tape from a 19th century case binding

By Maria Borg, Graduate Student, Books & Library Materials

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Among the various nineteenth century case bindings that rest on the shelves in the West Dean Books department awaiting treatment was one that was different to the rest. It was particularly appealing as its binding was completely covered in pressure-sensitive adhesive tape and it was therefore an interesting challenge to take on for a beginning book conservation student.

The book is a late nineteenth century copy of Andersen's Fairytales, complete with several illustrations (Fig. 1, 2). The entire cover was covered with pressure-sensitive adhesive tape and apart from the fact that in time it affects the materials of the book and will cause further damage, it was also visually jarring. It was initially thought that it had possibly even altered the original colour of the book cloth. The boards were still in good condition but the edges of the cloth cover were severely abraded which resulted in uncovered corners. The tape was turned in over the cloth and onto the pastedowns. In addition to this, there was an extensive loss of original material to the spine as there were only a few brittle fragments left which were held on solely by the tape. It seems that the tape was applied in order to protect the cover from further damage and to hold the various fragments together and prevent them from getting lost. Although the owner probably had good intentions, the application of the tape caused considerable other damage which affected both the materials of the book cover as well as the structure of the book.

This type of pressure- sensitive adhesive tape includes four main layers (Fig. 3). The adhesive mass is generally made of synthetic or natural rubber, whilst the carrier would be a flexible material that may be reinforced with other fibres. The primer coat is an important layer between the adhesive and the carrier to ensure sufficient adhesion takes place between the two. It adheres easily onto a range of substrates and does not require solvent or a liquid to stick well, nor does it need heat to activate the adhesive. As all other tapes, it undergoes stages of deterioration that cause damage to the substrate. At first, there is some time that very little is altered and it is reasonably easy to remove. However, after a longer period of time oxidation occurs and the adhesive becomes sticky, oily and yellow, staining the substrate. As oxidation continues to increase, the layer of adhesive mass gradually becomes less sticky. The result would be that the carrier would peel off, leaving adhesive residue on the substrate. The residue may remain slightly sticky, attracting dirt, causing further damage or forming crosslinks with the substrate. In this case the remnants of pressure-sensitive tape discolours, becomes more brittle and becomes even harder to remove. When peeling it from paper, the result could be the delamination of fibre layers in the paper.

For this reason, several tests had to be carried out in order to remove pressure-sensitive tape without causing damage to the original material. These were performed diligently and the treatments were applied to small areas in order to minimise the risks. First, heat was applied using a hot blower on interior top left corner of the left board and lifting the tape with a spatula (Fig. 4). Heat was considered to be a safe option to start with as it is easier to control. However, in tests this process was causing the pastedown to lift, and was thus discontinued. The second treatment tested was acetone, which was applied using a cotton swab and spatula, in order to lift the tape from the pastedown. However, this treatment was again causing the pastedown to lift and was discontinued. Heat was applied next, using a heated spatula and this proved to be successful. For this reason, the tape on the pastedown was removed using the heat spatula. However, it was decided that for the exterior cloth cover, heat would be applied using hot blower as this proved to be a successful given that it was a gentler treatment and the cloth was less affected by the pressure required to lift the tape.

Several tests also had to be conducted in order to remove the remaining adhesive residue, which was still sticky and could attract dirt and cause further problems. Attempts made using a crepe eraser (made from rubber and has a crinkled surface in order to help the mechanical action of cleaning, generally used to clean old adhesive residues from a variety of surfaces) and acetone (Fig. 6) both proved relatively effective. A Mars plastic eraser (a high-quality eraser that is phthalate and latex free, not crumble easily and leaves no discolouration of the eraser on the paper) successfully removed adhesive residue on certain areas of the paper, however it proved to be less successful in areas where adhesive residue was particularly thicker. Benzyl alcohol was considered to be another option. Both benzyl alcohol and acetone are polar solvents and therefore were considered to be more successful at dissolving natural resins. Benzyl alcohol was tested on a small area where the adhesive residue was particularly thick. Although it proved to be the most successful in removing traces of the residue, it also left a slight stain on the paper and therefore acetone was chosen as the best option to remove adhesive on the pastedowns and the cloth. It was applied using a cotton swab and the adhesive was removed by slow gentle strokes.

The next step in the process will be to consolidate the corners of the borders, infill any cloth losses and rebuild the spine. Although it felt a little daunting at times, this treatment was an intriguing process for me and a true learning experience. It was interesting to carry out tests, research different solvents and experience different applications and techniques. This was definitely one sticky situation I was happy to be in!

Figures 1 and 2. Left and right board of cloth case binding before treatment
Figure 3. Four components of pressure-sensitive tape. Source: http://cool.conservation-us.org/coolaic/sg/bpg/annual/v02/bp02-13.html
Figure 4. Test for removal of pressure-sensitive tape using heat blower
Figure 5. Removing adhesive residue using acetone applied with cotton swabs
Figure 6. Left and right board of cloth case binding after treatment