So, having thoroughly gone over The Key from top to bottom, front to back and left to right, now is the time to come up with a treatment proposal to stabilise it.
Conservation treatments don’t try to “restore” the item to its original state. Instead, conservators remove damaging materials and products as much as possible, stabilise the item once that threat is removed and place it into a storage environment where the ongoing deterioration will be slowed right down.
This item is a bit tricky though. As described previously, it was produced using iron salts suspended in gelatine which were developed in acidic chemicals. These acidic chemicals have not only made the paper quite brittle, but they seem to have damaged the residual gelatine as well.
A test was carried out on one of the small loose fragments of the print (about 1cm x 1.5cm). It was washed in deionized water and dried on a blotter.
NAA: A710, 51 - fragment after water wash, showing brown degradation product washed out
After this simple step the paper actually seemed thinner and softer, which poses the question: did some of the original material wash away (such as the residual gelatine), or did washing the degradation products out of the paper return it to a more flexible state? If it is the first scenario, it is a bad result – we wouldn’t want to remove original material irreversibly from the object. If it is the second scenario, it is a good result, as it has restored some flexibility to the paper, which may not now be as prone to physical damage.
What to do???
As much as we might like to try and wash the print with water to remove acidic degradation products, we run the risk of washing out the image as well, which would further reduce the density of the already faded lines. So, unfortunately, washing the print in water is probably out of the question.
Could we wash the print in an organic solvent to try and wash some of the degradation product out, but not risk solubilizing the image? A second fragment was washed in ethanol.
NAA: A710, 51 - fragment in ethanol bath
Unfortunately, nothing was washed out of the fragment, so this procedure wasn’t going to get us anywhere.
Forgetting about “wet” cleaning then, we can turn our attention to “dry” cleaning. The print can be surface cleaned (or “dry” cleaned) with erasers, front and back. This will remove loose surface dirt and brighten up the paper a bit. The front surface will have to be cleaned very carefully to avoid any pencil annotations, and to avoid disturbing the paper fibres which have become brittle and fragile with age.
Remember, too, this item is more than 2.3m long and 0.7m wide, so it is going to take QUITE A WHILE to surface clean it with a regular eraser!
Once the print has been cleaned, the masking tape will be removed so that the tears can be repaired more appropriately and more thoroughly. The full length of the tears will be repaired so that the whole vulnerable area is supported, rather than the current hit and miss approach.
NAA: A710, 51 - old repairs
The tears will be repaired using a thin tissue paper coated with a starch based adhesive. These are called “remoistenable” tissues and are something we make up in the lab. We make them ourselves so we can control the type of tissue used, the size of the sheet of tissue used and the formulation of the adhesive. The preparation of the tissue and a trial run of using them will be detailed in another blog post.
Once the individual tears have been repaired and allowed to dry, the entire print will be lined using whole sheets of remoistenable tissue. This will give strength to the object, keep it flat and provide a margin around the edges to hinge and mount the print for exhibition
The reason we use remoistenable tissue is so that we can tightly control how much moisture is being introduced to the object during the treatment. Too much moisture could cause the image to bleed, or tide lines to form (these are dark lines that form around small areas that wet out more than the adjacent areas)
NAA: A710, 51 - pre-existing tide lines
After the print has been lined onto tissue, the areas of loss will be in-filled with toned paper. This will serve to reduce the visual impact of the losses making them less distracting to the viewer.
Once the print has been repaired, it will be dried between acid free blotters, paper-makers felts and pressing boards to keep it flat and wrinkle free.
The last stage in the treatment will be to mat and house The Key for safe storage.
Stay tuned to see if it all goes to plan…