Paper is one of the most important carriers of cultural heritage, and its preservation is of vital importance. As a consequence of its degradation, volatile organic compounds (VOCs) are formed, which give rise to the memorable smell of old books. Their identity and quantity depends on paper composition and VOCs have been shown to be a source of information on paper quality and condition. This discovery enables the development of non-destructive 'sniffing' tools to rapidly identify the objects which are most at risk.
On the other hand, many simple organic acids, aldehydes and even aromatic compounds, formed during paper degradation, may also initiate or accelerate the degradation of cellulose, even from one document to another. A testing procedure was designed to quantify this effect and numerous preventive storage strategies were evaluated, from the use of VOC scavengers to hypoxia.
Impacts & Results
1. Volatile organic compounds (VOCs) are formed during degradation of paper and significantly contribute to its degradation.
2. Considering that the cumulative concentration of internally generated VOCs exceeds the concentrations of externally generated SO2, NOx and O3, the strategies of pollution mitigation in libraries and archives need to be reassessed, along with relevant standards. It has recently been shown that the stability of colour photographic is most affected by acetic acid .
3. The presence of groundwood-containing paper can up to double the rate of degradation of cellulose degraded in its proximity. While in repositories, separation of objects according to paper composition might therefore help, it is a resource intensive operation and would probably negatively affect collection management efficiency. However, alkaline sleeves could be used for groundwood-containing documents, thus beneficially affecting the object itself and those in the vicinity.
4. Strategies of removal of VOCs from the immediate proximity of paper have a positive effect on paper durability. The presence of moleculite and activated carbon, and hypoxic conditions have the same beneficial effect, which is most pronounced in the case of groundwood containing paper (up to 20% benefit). Paper sleeves with a good alkaline reserve also have a positive effect.
5. Different VOCs have different effects on the degradation of paper, with the effects of formic and acetic acid being comparable to that of some aldehydes (formaldehyde, vanillin and furfural). The negative effects of these compounds are most pronounced in the case of alkaline and neutral papers and less so in the case of acidic groundwood containing papers, which are themselves good emitters of VOCs.
6. Historic iron gall ink emits less VOCs than the surrounding paper (left, top), however, its effect on the degradation of paper stored in the proximity is still slightly negative because of the emission of reactive oxygen species (H2O2).
7. Archival boxes shield the documents from traffic-generated pollutants, however VOCs accumulate in the internal box environment. The concentration of acetic acid in boxes can thus exceed 100x that of NO2. Boxing materials should have a good alkaline reserve to absorb this acidity. Boxes with openings retain less VOCs (left, middle).
8. The VOCs emitted by paper have been shown to be a useful source of information on paper quality. Our research has shown, for the first time, that VOC emissions contain information on paper composition and condition. Based on this, development of sniffers to quickly identify the most endangered objects is possible.
9. There are no health concerns in view of aldehyde concentrations in libraries and archives (left, bottom). In poorly ventilated high-load repositories, the concentrations can exceed USA-NIOSH occupational limits (TWA - average value of exposure over the course of an 8 h work shift that is not to be exceeded) of 16 ppb.
10. A new test procedure has been proposed to evaluate the cross infection effect of storage materials in close proximity to organic heritage materials .
Cover image"Old books in Sarah's house" by lungstruck is marked with CC BY 2.0.