Agnieszka Depta, Conservator, Western Art on Paper, British Museum
After choosing the smallest possible eraser (yes, that’s the skinny one in the middle) to clean the largest print in the Prints and Drawings collection it didn’t seem like we would ever finish with the mammoth task of surface cleaning, but we did it and here is a picture of some of the eraser crumbs to prove it:
Before embarking onto the next step, to remove the soiled and degraded textile backing from the assembled pages, we supported delicate-looking creases and other weak areas with tissue and wheat starch paste. Then the print was turned over, which was no mean feat for a print this size (357 x 295 cm) and required all hands on deck.
First we carried out some tests to establish which method would be most appropriate to soften the starch-based adhesive so as to allow us to carefully peel the linen off the print in small strips. For this purpose it is best to introduce water very slowly, which allows the adhesive to gradually swell and soften without making the paper too wet. We have a choice of conservation-grade powders that will absorb and hold water in a gel or thick liquid, which we apply as a ‘poultice’. We sometimes use a fabric that holds moisture, such as a Microfibre cloth or capillary matting combined with a barrier material such as Gore-TexR which controls the rate of humidification.
Having settled on using a poultice, we removed the majority of the linen backing using this method. Some areas proved more difficult than others – perhaps where the paper was more deteriorated or thinner, or where the paste had been applied more thickly, or maybe different batches of paste were used. Akin to Goldilocks and her porridge, the poultice had to be left on the linen backing for just the right period of time: too short and some original paper fibres might be accidentally removed, too long and the paper would get soft and be at risk of damage. The goalposts changed as we moved across the print because of the variable topography but, as a reward for our patience, we got to know the print and its little quirks like a best friend. Getting up close and intimate with the print and observing the different styles of chamfering, pasting etc. allowed us to discover what a team effort it must have been to assemble and back it originally.
We too had to work as a team and during this period we were joined by students who observed the treatments and, for a few days of backing removal, by a fellow paper conservator Harry Metcalf, from the City Museum and Art Gallery, Bristol.
In order to reach the centre of the print, we started taking the individual sheets apart as soon as enough of the backing was removed to allow us to do so.
Unexpectedly, the joins had been thinned down in the past to the point where only a fragile layer of paper fibres remained, and it proved the greatest challenge of the project thus far to take the printed sheets apart safely. It required all our skill and ingenuity, including sourcing tools used in dentistry and even purchasing antique manicure sets on eBay and treating this like an exercise in micro-surgery. After weeks of painstaking labour the print has been taken apart into its original 38 sheets.
We also experimented with agarose gel strips (agarose is usually extracted from seaweed) to humidify the joins but the poultice applied on top of the linen, along the joints proved to be the most successful method. Most of the linen backing we removed was kept for possible future analysis and experimentation.
So far we have discovered that pieces of old prints were used to infill historical losses; there was also a notation made on the verso in red chalk; and the various watermarks on the different sheets are a lot more visible without the lining in place. Now that every sheet is easily accessible, it is apparent how creased and distorted some of the sheets are and we have an opportunity to note historical repairs of missing areas, other damage as well as record the watermarks in detail. Recording this detailed examination is currently underway.
Some of the infill paper at the edges proved very deteriorated and brittle and the adhesive tested acidic, putting the print at risk of further deterioration and confirming that it was high time to carry out conservation and perhaps something to keep in mind for when we might be secretly grumbling to ourselves ‘whose crazy idea was it to take this thing apart?’ when the time comes to fit all those sheets back together…. But before this happens, and after we have completed the documentation, we shall be carrying out treatments to reduce the old adhesive left on the back of the sheets as well as reduce the acidity, about which we will post an update on this blog in the near future.
The conservation of Dürer’s Triumphal Arch has been made possible by the generous support of Howard and Roberta Ahmanson.
You can see an interactive zoomable image of the print here.
You can see the removal of the textile backing here.