It is generally the case that a conservation treatment begins with surface cleaning. Dry particulate matter needs to be removed off the surface of the item so that any treatment steps involving liquids won’t drive that dirt further into the fibres of the paper.

This item, being so large, called for a cleaning technique that could cover broad areas of paper but be very gentle at the same time. The method chosen for the back was crumbed vinyl eraser.

Bag of eraser crumbs

This is worked onto the surface of the print using a gloved hand. The surface dirt sticks to the crumbs and they become discoloured. Once discoloured, the crumbs are brushed away, and fresh crumbs used in their place. This is repeated in a systematic way across the full length and width of the object until it is completely cleaned. Areas of pencil annotation were not cleaned so as to avoid erasing any of the pencil. Ink annotations can be cleaned very gently using this method. As you can see from the images, quite a bit of dirt was removed. Cleaning the back of the print in this manner took around 3 hours.

Working crumbed eraser over the surface of the print

Latex gloves after surface cleaning

These two techniques combined produce a successful outcome.

Localised cleaning before application of vinyl eraser

 

Localised cleaning after application of crumbed eraser

 

Localised cleaning after application of vinyl eraser

The front of the object was a different matter. It is much more damaged and fragile than the back. Cleaning the front was investigated very closely, including microscopic examination, to see if the paper fibres were being disturbed during cleaning.

Cheryl trials surface cleaning using a microscope

Unfortunately, they were being picked up, so neither crumbed eraser, nor solid vinyl eraser, was gentle enough. A similar print which has been treated in the lab previously was cleaned using a product called Smoke Sponge. This was used at the National Library after their fire in 1985 to clean soot from their books.
Used with a gentle dabbing motion rather than rubbing, the dirt can be picked up off the surface of the print with little impact of the paper fibers.

Cleaning a loose fragment using the smoke sponge

Smoke sponge after cleaning, showing adhered dirt

It was surprising how much dirt was removed (although the print didn’t actually look that much better – such is life!)

Again, areas of pencil annotation were avoided, but areas of ink annotation could be cleaned. Edges and tears also have to cleaned very carefully to avoid dislodging loose fibres or fragile edges.
Cleaning the front of the print in this manner took around 4 hours.
So in total, investigating and surface cleaning the print took a couple of days. It is not the sort of work you can do 8 hours straight. You need regular eye and muscle breaks. The work needs to be gentle on the body as well as the print.