Does dust attack paper? Spoiler alert: yes it does, but very little. But before going into details I will make a confession: sometimes heritage scientists are attracted by mayhem and destruction. Or, to be more precise, we can’t avoid disappointment when we find out that something is actually not too harmful to historic materials. Perhaps that happens because scientists generally dislike negative results – that is, results that do not show any relationship between two things. When we study the effects of an agent of deterioration (such as dust) on the long-term preservation of some material (such as paper), it leads us to a strange existential contradiction. For want of a better word we could call it scientific Schadenfreude, or a bittersweet scientific ennui: we don’t want heritage to be damaged in any away, but we really want our results to be positive. (If someone can think of a good term for this condition, I welcome suggestions.)
In one experiment, I studied whether dust deposition had any chemical effects on paper. We know that dirty surfaces don’t look good, and require cleaning, and we also know that excessive cleaning can lead to some physical damage. Beyond these factors of degradation, there was some reason to suspect that dust particles could be doing something more to a cellulosic substrate. After all, they are sometimes really small (see Figure 1) and can get deep into pores. Dust also has a very diverse composition, as it can originate from benign sources like a wool jumper, or really toxic ones like the combustion of diesel fuels.
So I devised a relatively simple experiment. I placed pieces of paper in several locations around London, exposing them to different types of dust. One of these locations was on the roof of the Wellcome Collection building. There I hoped to capture particles from the nearby Euston Road. And after a few months of exposure, I measured how the paper was doing and whether it was degraded at all. You can imagine that, as most heritage scientists would do, I was expecting a positive result. I would have been very happy if I had found a good evidence of degradation. The ideal result would be: the more dust, the more degradation. Perhaps this wouldn’t be a happy outcome for everyone, but the attraction of the positive result is strong. Scientists want to find out things, even if these things are not good. Maybe especially if these things are not good.
In any case, the relationship I found was, well, complicated. While in some cases the presence of dust had actually accelerated degradation, in others it didn’t. The key is the composition of the dust. Dust particles that originate from fossil fuels, containing traces of metals, can accelerate the degradation of paper. Dust particles from other sources don’t make a significant difference. But the good news is that even in the most extreme cases of soiling, when a piece of paper looks black with soot, the chemical effects only accelerate the rate of degradation by 10-20%. Nothing dramatic. It’s comparable to increasing the temperature of your storage areas by one or two degrees.
Heritage scientists need to learn to manage the attraction of the positive result. I could easily present this evidence with the following sentence: ‘The deposition of some types of dust results in a significant increase in the degradation rates of paper.’ This would be true, and there’s some satisfaction in being the author of such a weighty statement. But it would also be slightly irresponsible. It lacks context and could lead to incorrect preventive measures. I prefer to say, ‘Dust doesn’t usually degrade paper, except in some cases where it may have a small effect’. Dull? Perhaps. Maybe my article is not a harbinger of imminent destruction for paper collections. I should learn to live with the disappointment.
You can read the original paper (it’s open access) here: https://heritagesciencejournal.springeropen.com/articles/10.1186/s40494-016-0071-8
Josep Grau-Bove, an engineer by training, obtained his PhD in Heritage Science in 2015 and since then lectures at the UCL Institute for Sustainable Heritage. His main research interest is the use of mathematical models in preventive conservation, in order to understand how materials and the environment interact. He is also working on heritage citizen science, developing ways in which the public can help with data collection.